I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

Where can I get a 480 VAC drive for next to nothing? Used? Ebay? Please
explain. I think your concept is valid though.

"Ignoramus12852" wrote in message
...
I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

What about the output voltage? The one that you're bidding on is 480v
out. Is it programmable?

Bob

On 2007-10-07, Bob Engelhardt wrote:
What about the output voltage? The one that you're bidding on is 480v
out. Is it programmable?

The way VFDs work is, they rectify input voltage and then supply
the same voltage as "output", turning it on and off several times per
second. So the output voltage is, more or less, the input voltage.

i

On Oct 6, 10:45 pm, Ignoramus12852 ignoramus12...@NOSPAM.
12852.invalid wrote:
On 2007-10-07, Bob Engelhardt wrote:

What about the output voltage? The one that you're bidding on is 480v
out. Is it programmable?

The way VFDs work is, they rectify input voltage and then supply
the same voltage as "output", turning it on and off several times per
second. So the output voltage is, more or less, the input voltage.

i

Iggy dont most three phase motors relink to be a 240 or 480 so you
wouldnt even need to play with it?

What happens if you just feed the 480V VFD 240V?

other than that would you be able to find a three phase step down
transformer

Ignoramus12852 wrote:
I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

The control logic power supply is one thing. It would probably be worth
opening up the box to see if there are jumpers on the control power
primary that would allow the control electronics to run from 240V. You
already mentioned the undervoltage sense.

A few other things to consider would be the high voltage rectification
to DC and the output driver biasing.

If the high voltage rectification is power factor corrected which I
think is fairly likely, all bets are off. The power factor correction is
a boost converter that syncronously rectifies the incoming AC and
regulates the resulting DC to a voltage above the peak to peak AC input
voltage. This would have to be modified to boost to a different voltage.

If the high voltage recifier is a simple bridge, then the filter caps on
the high voltage DC supply and the recifier will still be sized for half
the current.

The output driver transistor biasing might or might not be OK at the
lower voltage. I assume that VFD's use IGBT outputs, so there is no
gate/base current to speak of like a bipolar transistor would require.

I would not bet even one beer that this would be as simple as just
getting the control electronics to run.

Good Luck,
BobH

On 2007-10-07, BobH wrote:
Ignoramus12852 wrote:
I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

The control logic power supply is one thing. It would probably be worth
opening up the box to see if there are jumpers on the control power
primary that would allow the control electronics to run from 240V. You
already mentioned the undervoltage sense.

A few other things to consider would be the high voltage rectification
to DC and the output driver biasing.

If the high voltage rectification is power factor corrected which I
think is fairly likely, all bets are off. The power factor correction is
a boost converter that syncronously rectifies the incoming AC and
regulates the resulting DC to a voltage above the peak to peak AC input
voltage. This would have to be modified to boost to a different voltage.

If the high voltage recifier is a simple bridge, then the filter caps on
the high voltage DC supply and the recifier will still be sized for half
the current.

The output driver transistor biasing might or might not be OK at the
lower voltage. I assume that VFD's use IGBT outputs, so there is no
gate/base current to speak of like a bipolar transistor would require.

I would not bet even one beer that this would be as simple as just
getting the control electronics to run.


Bob, I will try to find a cheap 480 v VFD and will play with it just
for the kicks. For maybe $15 or so, it will be a valuable educational
experience. I will try to find a 2 HP 480v VFD and will try to modify
it to run a 1 HP 240v motor. Worst case is, I will waste time and
money.

i

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i


It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.





I get flyers from automation direct that list single phase drives on
sale for less than 200 bucks new for a 1 hp drive. Unless you are
picking up the used drives for almost nothing, its not worth screwing
around with transfomrers and introducing more electrical losses and
potential problems in your system.


John

On 2007-10-07, Pete C. wrote:
Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.

If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i

john wrote:

Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i


It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

I get flyers from automation direct that list single phase drives on
sale for less than 200 bucks new for a 1 hp drive. Unless you are
picking up the used drives for almost nothing, its not worth screwing
around with transfomrers and introducing more electrical losses and
potential problems in your system.

John

That's my point. Unless you have say a half dozen 3ph machines in the 5
HP range, new individual 240V drives are a better idea. With those big
machines you could go the step-up and use 480V drives and save some
money potentially. Either way trying to modify the drives is almost
certainly not worth the effort.

Ignoramus3938 wrote:

On 2007-10-07, Pete C. wrote:
Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.

Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.


If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i

Ignoramus12852 wrote:
On 2007-10-07, BobH wrote:
Ignoramus12852 wrote:
I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.



Bob, I will try to find a cheap 480 v VFD and will play with it just
for the kicks. For maybe $15 or so, it will be a valuable educational
experience. I will try to find a 2 HP 480v VFD and will try to modify
it to run a 1 HP 240v motor. Worst case is, I will waste time and
money.

Please let me know how it works out. I did a component level repair on a
5 HP 240 volt unit, but it was only a matter of finding the roots of the
visibly exploded cap on the control board and replacing it. I did not
have a schematic and I suspect that they are hard to get.

The reason that I am expecting power factor correction on the high
voltage DC supply is that the Europeans have been raising a huge stink
about harmonic currents and power factor correction for about 5 or 7
years now on switching supplies and a motor drive is basicly a switching
supply. I think power factor correction is a legal requirement to sell
the drives in Europe for motor drives over a horsepower or so now.

Good Luck,
BobH

Pete C. wrote:

john wrote:

Pete C. wrote:


Ignoramus12852 wrote:


I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i


It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

I get flyers from automation direct that list single phase drives on
sale for less than 200 bucks new for a 1 hp drive. Unless you are
picking up the used drives for almost nothing, its not worth screwing
around with transfomrers and introducing more electrical losses and
potential problems in your system.

John


That's my point. Unless you have say a half dozen 3ph machines in the 5
HP range, new individual 240V drives are a better idea. With those big
machines you could go the step-up and use 480V drives and save some
money potentially. Either way trying to modify the drives is almost
certainly not worth the effort.




Most of the bigger drives use a transformer in front of them to switch
the input voltage.

Just as a side note, with vfds the motors don't always come with the
smoke alarm. It seems that the vfd limits the current and the smoke
doesn't release. I had one fail friday nite that didn't smoke. 25 hp
dc Reliance motor that just wanted to rotate to one position and stop.
The drive limits the current so the coils don't get too much of an
overload. On this motor there was a dead short to ground on the rotor.
The operator said that it had been rumbling for a while.

John

Pete C. wrote:

Ignoramus3938 wrote:

On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.


Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.


If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i



You will **** off the whole block, or whoever else is connected to your
pole transformer, as well as the electric company .


John

Pete C. wrote:
... new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time ...

The 480v drives can be *really* cheap. E.g.:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=150166657114

$23 *shipped* for 3hp at 480 or 1 1/2 at 240v

john wrote:

Pete C. wrote:

Ignoramus3938 wrote:

On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.


Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.


If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i

You will **** off the whole block, or whoever else is connected to your
pole transformer, as well as the electric company .

John

In my area that is one neighbor at most and in many cases it's one pole
pig to one residence. I share a 25KVA rated pole pig with one retired
neighbor and given the ability of a standard pole pig to handle 100%
overload (50KVA in my case) for 24hrs without damage I think I'm in good
shape.

On 2007-10-07, Pete C. wrote:
Ignoramus3938 wrote:

On 2007-10-07, Pete C. wrote:
Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.

Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.

A 40 HP 480 VFD would at most produce 20 HP off 240v, and 33% less
when derated to run from single phase. That leaves us with about 12 HP
at most.

i

Bob Engelhardt wrote:

Pete C. wrote:
... new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time ...

The 480v drives can be *really* cheap. E.g.:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=150166657114

$23 *shipped* for 3hp at 480 or 1 1/2 at 240v

I stand by my assertion. If you have a number of machines then you're
still better off with one step up transformer and running the 480V
drives at their rated 480V and strapping the motors in the machine for
480V to match the drives.

Pete C. wrote:

john wrote:

Pete C. wrote:


Ignoramus3938 wrote:


On 2007-10-07, Pete C. wrote:


Ignoramus12852 wrote:


I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.


Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.



If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i

You will **** off the whole block, or whoever else is connected to your
pole transformer, as well as the electric company .

John


In my area that is one neighbor at most and in many cases it's one pole
pig to one residence. I share a 25KVA rated pole pig with one retired
neighbor and given the ability of a standard pole pig to handle 100%
overload (50KVA in my case) for 24hrs without damage I think I'm in good
shape.




Its not so much that you will damage anything but your neighbor may get
****ed at his lights flickering. If the neighor is that old he'll
problaby think it was his eyes going bad.

The power company doesn't like sudden starts of motors or any load that
draws excessive current, especially if you are located on the end of the
supply line. It means that they have to upgrade their lines, and if
they know it's you doing it, you will learn about how a demand meter works.

On Oct 7, 7:16 pm, john wrote:


You will **** off the whole block, or whoever else is connected to your
pole transformer, as well as the electric company .

John



Its not so much that you will damage anything but your neighbor may get
****ed at his lights flickering. If the neighor is that old he'll
problaby think it was his eyes going bad.

The power company doesn't like sudden starts of motors or any load that
draws excessive current, especially if you are located on the end of the
supply line. It means that they have to upgrade their lines, and if
they know it's you doing it, you will learn about how a demand meter works.

That is another of the nice things about VFD's. They can start up a
motor slowly so no excessive current.

Dan

john wrote:

Pete C. wrote:

john wrote:

Pete C. wrote:


Ignoramus3938 wrote:


On 2007-10-07, Pete C. wrote:


Ignoramus12852 wrote:


I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.

I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.


Trying to run a 40 HP VFD on your 200A residential 240V service is sure
to let magic smoke out somewhere, not to mention ****ing off the wife
when the house power drops.



If you have enough machines that could use VFDs, you're likely better
off strapping their motors for 480V, buying the super cheap used 480V
VFDs, and finding a single good sized transformer to setup up the shop
240V to 480V to feed the drives.

That's definitely another practical possibility.

i

You will **** off the whole block, or whoever else is connected to your
pole transformer, as well as the electric company .

John


In my area that is one neighbor at most and in many cases it's one pole
pig to one residence. I share a 25KVA rated pole pig with one retired
neighbor and given the ability of a standard pole pig to handle 100%
overload (50KVA in my case) for 24hrs without damage I think I'm in good
shape.

Its not so much that you will damage anything but your neighbor may get
****ed at his lights flickering. If the neighor is that old he'll
problaby think it was his eyes going bad.

The power company doesn't like sudden starts of motors or any load that
draws excessive current, especially if you are located on the end of the
supply line. It means that they have to upgrade their lines, and if
they know it's you doing it, you will learn about how a demand meter works.

Demand metering is typically only allowed for the commercial rate
tariffs. I'm also about 1 mile from a regulator bank. The utility here
is pretty good actually, one day those regulators went out of whack and
gave me 136/272V. I called the utility and got a call back from a tech
in the area within 10 min, and in another 10 min he was parked in my
driveway and on the radio to another tech heading to the regulators.
Problem resolved in less than 30 min from my call.

On Sat, 06 Oct 2007 20:48:45 -0500, Ignoramus12852
wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i
Not impossible but you would have to know a lot about the
detail design of the drive and be prepared for a lot of messing
about with the printed circuit board.

The output stage should be OK but,in addition providing the
correct supply voltages to the control and drive circuits, you
would also need to modify the output voltage regulator system and
protection circuits to enable them to make them compatible with
the lower output voltage.

An interesting project for the hardened experimenter with
adequate experience and test equipment but not a job to be
undertaken lightly!

Jim

wrote:

On Sat, 06 Oct 2007 20:48:45 -0500, Ignoramus12852
wrote:


I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

Not impossible but you would have to know a lot about the
detail design of the drive and be prepared for a lot of messing
about with the printed circuit board.

The output stage should be OK but,in addition providing the
correct supply voltages to the control and drive circuits, you
would also need to modify the output voltage regulator system and
protection circuits to enable them to make them compatible with
the lower output voltage.

An interesting project for the hardened experimenter with
adequate experience and test equipment but not a job to be
undertaken lightly!

Jim



The hardest part is to get a copy of the schematic of the drive so you
dont have to guess what is going on in it.

The phase rotation sensor and phase loss sensors would have to be
bypassed if you are running on single phase.

The current sensors would probably be ok since the high power
electronics ratings are already matched for the current setting of the
sensor. The voltage sensors would have to be modified for the lower
voltage on the DC buss.

The control circuits power supply would have to be modified to take the
lower ac input voltage unless is was a switching supply with a wide
range of input voltages.

the final thing is that higher powered drives are expensive, even the
480 volt ones since there is a continous demand for them. A new 40 hp
drive gets up in price.


John

On Sun, 07 Oct 2007 18:06:36 GMT, "Pete C."
wrote:

Bob Engelhardt wrote:

Pete C. wrote:
... new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time ...

The 480v drives can be *really* cheap. E.g.:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=150166657114

$23 *shipped* for 3hp at 480 or 1 1/2 at 240v

I stand by my assertion. If you have a number of machines then you're
still better off with one step up transformer and running the 480V
drives at their rated 480V and strapping the motors in the machine for
480V to match the drives.


And I agree with it 100%

Gunner

Pete C. wrote:
Bob Engelhardt wrote:
Pete C. wrote:
... new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time ...

The 480v drives can be *really* cheap. E.g.:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=150166657114

$23 *shipped* for 3hp at 480 or 1 1/2 at 240v

I stand by my assertion. If you have a number of machines then you're
still better off with one step up transformer and running the 480V
drives at their rated 480V and strapping the motors in the machine for
480V to match the drives.

Ah, well - I was responding to your assertion that "...new drives up to
a couple HP are in the $200-300 range ...", not to the "If you have a
number of machines ...". That was why I only quoted that part of your post.

Bob

Ignoramus12852 wrote:
I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage.
Most modern VFDs use a little inverter off the main DC supply,
not a separate 60 Hz transformer.
They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

Yes, they most certainly do, and will shut down below some
particular voltage.
So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).
Well, the little inverter could be rewound, or replaced with a
60 Hz transformer, once you figure out the several DC voltages
it supplies to the works. Then, you could track down the
resistor voltage divider for the voltage sensing and change
that. You would have to convert various things when programming
the drive, because it still thinks it is producing 480 output.
All the current logic should work fine without any changes or
conversions, and Hz is still Hz. If you could find a 5 Hp 480 V
VFD, that would make a dandy 1 Hp 240 V VFD, if the above
conversions weren't too hard to accomplish. If you found a
pallet of 480 V VFDs of the same make and model, this could be a
very profitable exercise. I'm not sure it would be such a great
deal to have to trace all this out on a one-by-one basis.

Jon

Brent wrote:
On Oct 6, 10:45 pm, Ignoramus12852 ignoramus12...@NOSPAM.
12852.invalid wrote:

On 2007-10-07, Bob Engelhardt wrote:


What about the output voltage? The one that you're bidding on is 480v
out. Is it programmable?

The way VFDs work is, they rectify input voltage and then supply
the same voltage as "output", turning it on and off several times per
second. So the output voltage is, more or less, the input voltage.

i


Iggy dont most three phase motors relink to be a 240 or 480 so you
wouldnt even need to play with it?

What happens if you just feed the 480V VFD 240V?
It would say something like "UV" in the display, and refuse to
do anything.

Jon

BobH wrote:
Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.
They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.
So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).
What am I missing?


The control logic power supply is one thing. It would probably be worth
opening up the box to see if there are jumpers on the control power
primary that would allow the control electronics to run from 240V. You
already mentioned the undervoltage sense.

A few other things to consider would be the high voltage rectification
to DC and the output driver biasing.

If the high voltage rectification is power factor corrected which I
think is fairly likely, all bets are off.
The smaller drives, ie. 1 - 15 Hp, in the US at least, never
seem to have PFC. This may be totally different in Europe.
Many of the bigger drives have an inrush surge limiting circuit
that may not switch over properly at half voltage - but they may
just be a timer circuit off the control power.
The output driver transistor biasing might or might not be OK at the
lower voltage. I assume that VFD's use IGBT outputs, so there is no
gate/base current to speak of like a bipolar transistor would require.

They derive all this off the control power, so it should be
fine, once you get the control power supply working right.

Jon

Ignoramus3938 wrote:
On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.


I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no
losses, and just steady state running, would draw 15 KW, and 62
A at 240 V. If the starting surge was only 100%, that would
take it up to 124 A. You won't need much else on in your entire
house to trip the service entry breaker.

Jon

wrote:
Not impossible but you would have to know a lot about the
detail design of the drive and be prepared for a lot of messing
about with the printed circuit board.

The output stage should be OK but,in addition providing the
correct supply voltages to the control and drive circuits, you
would also need to modify the output voltage regulator system and
protection circuits to enable them to make them compatible with
the lower output voltage.

There is no "output voltage regulator". The CPU measures DC bus
voltage and calculates the correct pulse width to get the
desired voltage. If you hack the resistor voltage divider so
the CPU reads the expected voltage when it is really half of
that, it will calculate the right pulse width. You still tell
it it is running a 480 V motor, and it dutifully puts out 240 V
due to the two changes (reduced DC voltage, incresed sense
voltage) cancelling out.
An interesting project for the hardened experimenter with
adequate experience and test equipment but not a job to be
undertaken lightly!
Iggy is INDEED a hardened experimenter, who hacked a DC TIG
welder into a square wave AC TIG machine. So, I think he COULD
do this. I don't know if it makes any sense to do just one
unit, but if you had a bunch of the same model, it could be
quite a successful project.

Jon

john wrote:
The hardest part is to get a copy of the schematic of the drive so you
dont have to guess what is going on in it.

The phase rotation sensor and phase loss sensors would have to be
bypassed if you are running on single phase.

I can't imagine any reason a VFD would have a phase sequence
sensor, as it just gets rectified to DC anyway. Some drives do,
and some don't have a phase loss sensor. But, since Iggy was
talking about 40+ Hp drives, then they often do have that.
The current sensors would probably be ok since the high power
electronics ratings are already matched for the current setting of the
sensor. The voltage sensors would have to be modified for the lower
voltage on the DC buss.

That's only one resistor, but you have to know enough to find it.
The control circuits power supply would have to be modified to take the
lower ac input voltage unless is was a switching supply with a wide
range of input voltages.

It is customarily a switching supply off the main DC bus on most
modern drives. And, they usually are not very wide range.

Jon

On 2007-10-08, Pete C. wrote:
Jon Elson wrote:

Ignoramus3938 wrote:
On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.


I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no
losses, and just steady state running, would draw 15 KW, and 62
A at 240 V. If the starting surge was only 100%, that would
take it up to 124 A. You won't need much else on in your entire
house to trip the service entry breaker.

Jon

My TIG welder (I think Iggy's as well) will happily suck down 100A at
240V, and for longer than that motors startup too. I haven't had any
problems yet.

Mine draws about 60 amps.

i

On 2007-10-08, Jon Elson wrote:
Ignoramus3938 wrote:
On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.


I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no
losses, and just steady state running, would draw 15 KW, and 62
A at 240 V. If the starting surge was only 100%, that would
take it up to 124 A. You won't need much else on in your entire
house to trip the service entry breaker.

Derate it to 20 HP due to voltage, then derate it to about 66% of that
due to single phase, you get just 12-13 HP. I routinely start a 10 HP
motor at home (in my phase converter) and that is never a problem (60
A circuit).

I read all your posts in this thread with huge interest. I will keep
trying to get a cheap 480v drive to play with. I estimate my chances
of success at about 20-30%. But I will learn something useful.

i

Ignoramus17253 wrote:

On 2007-10-08, Jon Elson wrote:
Ignoramus3938 wrote:
On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.


I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no
losses, and just steady state running, would draw 15 KW, and 62
A at 240 V. If the starting surge was only 100%, that would
take it up to 124 A. You won't need much else on in your entire
house to trip the service entry breaker.

Derate it to 20 HP due to voltage, then derate it to about 66% of that
due to single phase, you get just 12-13 HP. I routinely start a 10 HP
motor at home (in my phase converter) and that is never a problem (60
A circuit).

I read all your posts in this thread with huge interest. I will keep
trying to get a cheap 480v drive to play with. I estimate my chances
of success at about 20-30%. But I will learn something useful.

i

Look for a transformer while you're at it. They should be readily
available, my own inventory has a number from 1KVA to 15KVA. They
typically have dual pri and sec windings so 240/480:120/240 however you
care to connect them.