VFD idle power use
 

I have an apple packing line that runs on three phase. It has four 3/4 hp.
motors and a hoist (1/2 hp) I leave the three phase ilder on 12 hours a day
seven days a week. I'm trying to trim my $600 monthly fall electric bill.
(mostly 5hp cooler) I get 7 amps usage while none of the packing line is
running. It would be nice to get rid of the motor hum also.

My question, would a VFD work well to provide three phase for this packing
line. Is standby power usage on a VFD near 0? I'd have to bring motors in
with the existing control logic and wire VFD so it always powers the output
legs.

Karl

VFD as 3P power source or controls for your motors?

Here's a stupid question...why not just turn it off when not in use?

"Karl Townsend" remove .NOT to reply wrote
in message k.net...
I have an apple packing line that runs on three phase. It has four 3/4 hp.
motors and a hoist (1/2 hp) I leave the three phase ilder on 12 hours a
day
seven days a week. I'm trying to trim my $600 monthly fall electric bill.
(mostly 5hp cooler) I get 7 amps usage while none of the packing line is
running. It would be nice to get rid of the motor hum also.

My question, would a VFD work well to provide three phase for this packing
line. Is standby power usage on a VFD near 0? I'd have to bring motors in
with the existing control logic and wire VFD so it always powers the
output
legs.

Karl

On Sat, 27 Aug 2005 17:20:47 GMT, "Karl Townsend"
remove .NOT to reply wrote:

I have an apple packing line that runs on three phase. It has four 3/4 hp.
motors and a hoist (1/2 hp) I leave the three phase ilder on 12 hours a day
seven days a week. I'm trying to trim my $600 monthly fall electric bill.
(mostly 5hp cooler) I get 7 amps usage while none of the packing line is
running. It would be nice to get rid of the motor hum also.

My question, would a VFD work well to provide three phase for this packing
line. Is standby power usage on a VFD near 0? I'd have to bring motors in
with the existing control logic and wire VFD so it always powers the output
legs.

I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

My problem with VFD's is that they're so danged complicated. There
are a buncha settings to get right. Maybe some of them have
"default" values you can invoke if all you want is 3 phase 60 Hz.

I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

I get 15 cents per hour(7amp*220Volt*$0.10/KwHr), or about $54 per month, or
$270 per season as my estimate. I've got no way to check power factor. Just
watching the meter, you can see it turns way more than the load from all the
lights being on in the barn.(1200 watts total). If the VFD has virtually 0
power use at no load, there is enough savings to install it here.


My problem with VFD's is that they're so danged complicated. There
are a buncha settings to get right. Maybe some of them have
"default" values you can invoke if all you want is 3 phase 60 Hz.

I've got VFDs on the mill and lathe. They both ran right outa the box. I
agree there's a ton of parameters. Most all of them will run just fine at
defaults.


To answer another fellow's question, we pack apples between each customer
visit all day long. We'd be turning it on/off fifty times a day to shut it
off when not running. Not practical. We turn on the lights and phase
converter when we open the door in the morning, and off when we lock up.

Karl

"Karl Townsend" remove .NOT to reply wrote
in message nk.net...


I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

I get 15 cents per hour(7amp*220Volt*$0.10/KwHr), or about $54 per month,
or $270 per season as my estimate. I've got no way to check power factor.
Just watching the meter, you can see it turns way more than the load from
all the lights being on in the barn.(1200 watts total). If the VFD has
virtually 0 power use at no load, there is enough savings to install it
here.


My problem with VFD's is that they're so danged complicated. There
are a buncha settings to get right. Maybe some of them have
"default" values you can invoke if all you want is 3 phase 60 Hz.

I've got VFDs on the mill and lathe. They both ran right outa the box. I
agree there's a ton of parameters. Most all of them will run just fine at
defaults.


To answer another fellow's question, we pack apples between each customer
visit all day long. We'd be turning it on/off fifty times a day to shut it
off when not running. Not practical. We turn on the lights and phase
converter when we open the door in the morning, and off when we lock up.

Karl

Karl

Your estimate of the idler's power draw at no load indicates that the
idler might be consuming about 2 HP. How big is the idler?

Jerry

"Karl Townsend" remove .NOT to reply wrote
in message k.net...
I have an apple packing line that runs on three phase. It has four 3/4 hp.
motors and a hoist (1/2 hp) I leave the three phase ilder on 12 hours a day
seven days a week. I'm trying to trim my $600 monthly fall electric bill.
(mostly 5hp cooler) I get 7 amps usage while none of the packing line is
running. It would be nice to get rid of the motor hum also.

My question, would a VFD work well to provide three phase for this packing
line. Is standby power usage on a VFD near 0? I'd have to bring motors in
with the existing control logic and wire VFD so it always powers the
output legs.

Karl

VFDs don't seem to create much heat when idling, so I can't imagine they're
using much power. I've never checked one with a wattmeter, though.

In article et,
Karl Townsend remove .NOT to reply wrote:


I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

I get 15 cents per hour(7amp*220Volt*$0.10/KwHr), or about $54 per month, or
$270 per season as my estimate.

Do you have a power-factor correction capacitor on the rotary
converter? What you do is connect AC run capacitors between the two
sides of the 220V line as it enters the rotary converter, measuring the
current in one of those legs (between the circuit breaker and where you
add the capacitors), until you get a minimum current. Past a certain
amount of added capacitance, you will start to increase the current
again.

Anyway -- the current at the minimum will be pretty much the
"real" current, and any above that will be "imaginary" current. (They
add at 90 degrees, so you can't really just add them, but for most power
services, the "real" current is all that you are charged for, and the
benefits of tuning the power factor are mostly less heating of the wires
and less chance of nuisance trips at the circuit breaker (if your "real"
+ "imaginary" current takes it close to the trip point.)

I've got no way to check power factor. Just
watching the meter, you can see it turns way more than the load from all the
lights being on in the barn.(1200 watts total). If the VFD has virtually 0
power use at no load, there is enough savings to install it here.

It does, indeed.

The problem with using a single VFD for driving several machines
is that you are then tempted to switch the power to the individual
machines between the VFD and the machine, instead of setting things up
so the machine commands the VFD to apply power or not to the machine.

Switching between the VFD and the machine increases the risk of
damaging the output circuits of the VFD with the switching spikes. I've
gotten away with it when using a 1 hp milling machine on a 7-1/2 hp VFD,
but I'm not sure how long I will get away with it even with that big a
difference between capacity and load.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

On Sun, 28 Aug 2005 03:07:37 GMT, "Karl Townsend"
remove .NOT to reply wrote:



I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

I get 15 cents per hour(7amp*220Volt*$0.10/KwHr), or about $54 per month, or
$270 per season as my estimate. I've got no way to check power factor. Just
watching the meter, you can see it turns way more than the load from all the
lights being on in the barn.(1200 watts total). If the VFD has virtually 0
power use at no load, there is enough savings to install it here.


My problem with VFD's is that they're so danged complicated. There
are a buncha settings to get right. Maybe some of them have
"default" values you can invoke if all you want is 3 phase 60 Hz.

I've got VFDs on the mill and lathe. They both ran right outa the box. I
agree there's a ton of parameters. Most all of them will run just fine at
defaults.


To answer another fellow's question, we pack apples between each customer
visit all day long. We'd be turning it on/off fifty times a day to shut it
off when not running. Not practical. We turn on the lights and phase
converter when we open the door in the morning, and off when we lock up.

Karl

OK. So when should I visit to get some Honeycrisp apples?

....

OK. So when should I visit to get some Honeycrisp apples?

I've got a monster crop this year. They'll start Sept 24 and go to Dec 18
(last day open) I've got discounts for Semi truck loads.

Karl

Your estimate of the idler's power draw at no load indicates that the
idler might be consuming about 2 HP. How big is the idler?


5 hp. idler.

I've got a 5 hp VFD waiting for my Hardinge upgrade. I think I'll stick it
in and try it for the fall.

Karl

"DoN. Nichols" wrote in message
...
In article et,
Karl Townsend remove .NOT to reply
wrote:


I'd first check the no-load power consumption of the idler. If it's 7
amps at near 0 power factor, it doesn't cost much to run. Just
watch the electric meter for a little while with the idler being the
only load running. That (and a bit of calculation) will tell you
cost per hour of the idler's overhead.

I get 15 cents per hour(7amp*220Volt*$0.10/KwHr), or about $54 per month,
or
$270 per season as my estimate.

Do you have a power-factor correction capacitor on the rotary
converter? What you do is connect AC run capacitors between the two
sides of the 220V line as it enters the rotary converter, measuring the
current in one of those legs (between the circuit breaker and where you
add the capacitors), until you get a minimum current. Past a certain
amount of added capacitance, you will start to increase the current
again.

Anyway -- the current at the minimum will be pretty much the
"real" current, and any above that will be "imaginary" current. (They
add at 90 degrees, so you can't really just add them, but for most power
services, the "real" current is all that you are charged for, and the
benefits of tuning the power factor are mostly less heating of the wires
and less chance of nuisance trips at the circuit breaker (if your "real"
+ "imaginary" current takes it close to the trip point.)

I've got no way to check power factor.
Just
watching the meter, you can see it turns way more than the load from all
the
lights being on in the barn.(1200 watts total). If the VFD has virtually 0
power use at no load, there is enough savings to install it here.

It does, indeed.

The problem with using a single VFD for driving several machines
is that you are then tempted to switch the power to the individual
machines between the VFD and the machine, instead of setting things up
so the machine commands the VFD to apply power or not to the machine.

Switching between the VFD and the machine increases the risk of
damaging the output circuits of the VFD with the switching spikes. I've
gotten away with it when using a 1 hp milling machine on a 7-1/2 hp VFD,
but I'm not sure how long I will get away with it even with that big a
difference between capacity and load.

Enjoy,
DoN.

One VFD for each machine is really the right way to do it. Not really that
expensive for the small motors involved. I wouldn't be surprised if the
occasional nuisance fault shuts the line down. We found that out with
heating circulators- all of a sudden you put a VFD on and you're dealing
with another point of possible failure.

In article . net, Karl Townsend
says...

Your estimate of the idler's power draw at no load indicates that the
idler might be consuming about 2 HP. How big is the idler?


5 hp. idler.

How were you measuring that 7 amp current draw?

With an amp-clamp meter, right?

Well it was giving you the number that you didn't need to
know - it was giving you the total of both in-phase *and*
out-of-phase current.

The phase angle for the current flowing an unloaded idler
motor like that is about 90 degrees. It's not real current
and won't spin your meter.

Get a proper test setup to measure the phase angle and compute
the *real* power while it's unloaded, and you will see your
idler runs between 200 and 250 watts, most likely. That's
the result I found with my 5hp converter.

My estimation is that your converter is not what's costing
you the money.

Jim


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OK, Karl. Don't forget the sack you owe me from a couple years back.

Bob Swinney
"Karl Townsend" remove .NOT to reply wrote
in message nk.net...

...

OK. So when should I visit to get some Honeycrisp apples?

I've got a monster crop this year. They'll start Sept 24 and go to Dec 18
(last day open) I've got discounts for Semi truck loads.

Karl