I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.


--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
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In article ,
Ignoramus19266 wrote:

I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.

What make and model of VFD?

What does the VFD manual say?

How is it connected to the single-phase feed?

How big is the big capacitor?

Joe Gwinn

On 2009-02-21, Ignoramus19266 wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

Just out of curiosity -- was the single-phase measurement taken
by simply removing one of the three three-phase wires to the VFD, or by
plugging it into a single-phase outlet?

And -- IIRC, your three phase comes from a rotary converter, so
the balance may be a bit off. Try measuring between each pair of
terminals. The voltage in the capacitor under low or no load will be
purely determined by whichever phase pair has the highest voltage
assuming a standard three phase bridge rectifier.

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

Are you sure that all three phases measure the same voltage?
Check that out before you assume that you are providing truly the same
input voltage.

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

If it is truly sensing only the voltage in the capacitor, try a
Variac (with the overvoltage wiring option) to see what voltage you need
to reach to turn off the fault indication. Once you find the needed
voltage, subtract the line voltage from it. Look for a filament
transformer or something similar which produces a bit more than that
difference, and wire the primary across the 240 VAC line, and the
secondary in series with the 240 VAC line to boost the voltage by that
much. Obviously, you need the secondary current capability to be high
enough to match what the VFD will draw at full load.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.

That would probably work, too. It it an autotransformer or an
isolation transformer?

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2009-02-21, Joseph Gwinn wrote:
In article ,
Ignoramus19266 wrote:

I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.

What make and model of VFD?

Omegapak 10 HP VFD , Omegapak VFD 8803 Type P00CO2H.

Manual is he

http://igor.chudov.com/manuals/Omega...que-Manual.pdf

What does the VFD manual say?

It says that Phase Fault detection is done by looking at the DC
bus. At least how I interpret page 11 of the manual above, and the
measurement board 7.

How is it connected to the single-phase feed?

Through the rectifier.

How big is the big capacitor?

3,500 uF.


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Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
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On 2009-02-21, DoN. Nichols wrote:
On 2009-02-21, Ignoramus19266 wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

Just out of curiosity -- was the single-phase measurement taken
by simply removing one of the three three-phase wires to the VFD, or by
plugging it into a single-phase outlet?

Both.

And -- IIRC, your three phase comes from a rotary converter, so
the balance may be a bit off. Try measuring between each pair of
terminals. The voltage in the capacitor under low or no load will be
purely determined by whichever phase pair has the highest voltage
assuming a standard three phase bridge rectifier.

Yes, I sort of agree. But I tried everything, specifically I tried
connecting the phase with highest voltage to the L1 and L2 inputs.

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

Are you sure that all three phases measure the same voltage?
Check that out before you assume that you are providing truly the same
input voltage.

Slightly different indeed.

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

If it is truly sensing only the voltage in the capacitor, try a
Variac (with the overvoltage wiring option) to see what voltage you need
to reach to turn off the fault indication. Once you find the needed
voltage, subtract the line voltage from it. Look for a filament
transformer or something similar which produces a bit more than that
difference, and wire the primary across the 240 VAC line, and the
secondary in series with the 240 VAC line to boost the voltage by that
much. Obviously, you need the secondary current capability to be high
enough to match what the VFD will draw at full load.

After a lot of thinking, I am beginning to suspect that the VFD does
more than just monitor bus voltage. I will try to ascertain facts a
little better before going on the assumption that only bus voltage is
the issue.


I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.

That would probably work, too. It it an autotransformer or an
isolation transformer?

Isolation.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Ignoramus19266 wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

240 V (single phase) AC full-wave rectified and
filtered, should be around 340 V.

sqrt(2) * 240

Dropping to 314 V (I presume only nder load) seems
to suggest either a lot of resistance in the feed
or too little capacitance on the DC bus.
I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

Oh, now this makes no sense at all! Check your
rectifiers, I'll bet you have a bad one, and you
are only getting half-wave rectification. Hmm,
maybe your line voltage is just very low. You'd
get 314 V DC from mains at 222 VAC (RMS).
I suppose your mains could get that low and still
be considered within tolerance.
Your VFD obviously was not designed to operate on
208 V 3-phase.

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.


If the problem is truly your mains voltage, a
little boost should work, but watch out when the
mains go to the high side. Do you have a line
reactor on the rectifier? It may have too much
inductance and is lowering your voltage. What IS
you mains voltage when the problem is observed?

Jon

Ignoramus19266 wrote:

After a lot of thinking, I am beginning to suspect that the VFD does
more than just monitor bus voltage. I will try to ascertain facts a
little better before going on the assumption that only bus voltage is
the issue.
Ugh! If it uses an algorithm to detect the ripple
frequency in the DC bus, you have a big problem.
If it sees 360 Hz ripple, all is OK, if it sees
120 Hz ripple, give phase fault indication.

That would be bad news, and if it is in the
microcontroller's firmware, really hard to get around.

But, you ALSO see a large dip in DC voltage, which
I find really hard to understand, especially at no
load. Given the thing is probably drawing just a
few watts to drive the electronics, (and I think
most of that was supposed to come from the control
supply, powered separately) there should be
extremely little ripple and the DC voltage should
go all the way up to 1.414 * RMS line voltage.
That has to be the key, and until you know why it
is well below this, the rest is speculation.

Jon

On Feb 20, 7:11*pm, Ignoramus19266 ignoramus19...@NOSPAM.
19266.invalid wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: *342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

* * ** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:


Special functions,
Phase Failure Fault Enable, p.133

Jim Wilkins

I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

On 2009-02-21, Jim Wilkins wrote:
On Feb 20, 7:11?pm, Ignoramus19266 ignoramus19...@NOSPAM.
19266.invalid wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: ?342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

? ? ** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:


Special functions,
Phase Failure Fault Enable, p.133

Jim Wilkins

Jim, this is very cool, but this function requires a programmer
interface for it? (separate programmer module) Is that right?
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Ignoramus19266 wrote:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

I think so. Single phase for one cycle looks like mcdonalds' arches. Three phase is a
lot smoother.

http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

Go down to the bottom. Not a lot of area above the curve.

Your meter reads root mean square.

http://en.wikipedia.org/wiki/Root_mean_square

Wes

On Feb 21, 12:51*am, Ignoramus19266 ignoramus19...@NOSPAM.
19266.invalid wrote:
On 2009-02-21, Jim Wilkins wrote:





On Feb 20, 7:11?pm, Ignoramus19266 ignoramus19...@NOSPAM.
19266.invalid wrote:
I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: ?342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

? ? ** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

Special functions,
Phase Failure Fault Enable, p.133

Jim Wilkins

Jim, this is very cool, but this function requires a programmer
interface for it? (separate programmer module) Is that right?

I'm not going to study the whole manual for two days and don't know
what you have available for tools anyway. I only speed-read it as it
scrolled down the screen. There is a 9600 baud serial connection,
maybe you can write a program to send command strings or read out the
flash memory settings.

I connect to a Radio Shack multimeter in QBasic with
OPEN "COM2:600,N,7,2,RS,CS,DS,CD" FOR RANDOM AS 2
600 Baud, No_parity, 7_data_bits, 2_stop_bits, the rest shut off
control line timeouts.

SELECT CASE makes a quick parser you can easily add to. I usually
check for user input with INKEY$ and exit with CASE CHR$(27):EXIT DO.
This limits input to single keys but allows ESCape, doesn't require
ENTER although it sees it as CHR$(13), and the program is free to poll
the device instead of looping on the keyboard. I haven't figured out
how to poll the serial port's I/O memory for data yet and set BREAK so
I can exit when the data string doesn't satisfy INPUT.

Whenever I have to figure out some complicated computerized device
whose designer and programmer have quit I experiment on something
harmless and obvious like toggling an unused or advisory function
before risking serious changes. The big first step is getting a
response from a ping.

Wes, most meters read Average and scale it to the equivalent RMS
value. If they read RMS they'll say so.

Jim Wilkins

In article ,
Ignoramus19266 wrote:

On 2009-02-21, Joseph Gwinn wrote:
In article ,
Ignoramus19266 wrote:

I have been trying to make my 10 HP VFD accept single phase input. (it
works GREAT with three phase input) It gives me a phase
fault. According to the schematic, the only way it detects phase fault
is by drops in bus voltage.

I added a big DC capacitor and it is not helping.

I measured bus voltage.

Single phase input: 314 volts
Three phase input: 342 volts

I also tried to connect L2 to L3 and it did not fix the phase fault.

** ALL OF THIS IS IN COMPLETE ABSENCE OF LOAD **

So, assuming that phase fault is detected by bus voltage:

1) Is that really true that three phase rectifier would give a higher
bus voltage than single phase (given same input voltage)

2) What can I practically do to cheat this device and make it accept
DC generated by single phase.

I do have a 10 KVA ACME transformed that I could use to boost the
input voltage from, say, 230v to 250v or some such.

What make and model of VFD?

Omegapak 10 HP VFD , Omegapak VFD 8803 Type P00CO2H.

Manual is he

http://igor.chudov.com/manuals/Omega...que-Manual.pdf

What does the VFD manual say?

It says that Phase Fault detection is done by looking at the DC
bus. At least how I interpret page 11 of the manual above, and the
measurement board 7.

I read it the same way. Others have suggested that the phase fault
detection might be keyed on presence of 360 Hz ripple, but even
rectified single phase has significant 360 Hz ripple, so I'm not sure
that loss of a single phase of three phase would reduce the 360 Hz
signal enough to be a reliable way to tell, so the detection algorithm
is probably different than simple 360 Hz detection.

Constraints on the algorithm include the following:

The scheme cannot depend too much on exact power frequency.

It must be immune to variations in supply voltage over the nameplate
range of input voltages.

The signal being thresholded to declare a fault or no fault must clearly
differ if any single phase is lost.

It must be possible to low-pass filter the signal, to eliminate nuisance
tripping due to noise.


Ripple voltage as a ratio to DC voltage is simple, and may well be
reliable enough.

More reliable but more complex would be the ratio of powers in DC and
harmonics.


How is it connected to the single-phase feed?

Through the rectifier.

My question was how S1 and S2 (incoming one-phase line) are connected to
L1, L2, L3.

Others have speculated that there might be a blown rectifier. If only
one rectifier is gone, changing which terminals are driven from single
phase may solve the problem.


How big is the big capacitor?

3,500 uF.

You should be achieving almost peak voltage at low 3-phase load.

Joe Gwinn

Wes writes:


Your meter reads root mean square.

http://en.wikipedia.org/wiki/Root_mean_square

Maybe. Many meters don't; other claim they do, but only if the waveform
is... where the 'if' is signifiant.

Diode rectification of sine waves is not a difficult case. Switching
power supplies, however.....

For a long time, RMS meters measured same by basics -- heating
value. They used a resistive load and measured its temperature.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

If I were designing that circuit, I'd put a resister in front of each
diode pair,and one behind the output. If you only had two phases you
would get the big voltage drop that Iggy sees. Adding a cap won't help.

Jon Elson wrote:
Ignoramus19266 wrote:

After a lot of thinking, I am beginning to suspect that the VFD does
more than just monitor bus voltage. I will try to ascertain facts a
little better before going on the assumption that only bus voltage is
the issue.
Ugh! If it uses an algorithm to detect the ripple frequency in the DC
bus, you have a big problem. If it sees 360 Hz ripple, all is OK, if it
sees 120 Hz ripple, give phase fault indication.

That would be bad news, and if it is in the microcontroller's firmware,
really hard to get around.

But, you ALSO see a large dip in DC voltage, which I find really hard to
understand, especially at no load. Given the thing is probably drawing
just a few watts to drive the electronics, (and I think most of that was
supposed to come from the control supply, powered separately) there
should be extremely little ripple and the DC voltage should go all the
way up to 1.414 * RMS line voltage. That has to be the key, and until
you know why it is well below this, the rest is speculation.

Jon

RoyJ writes:

If I were designing that circuit, I'd put a resister in front of each
diode pair,and one behind the output. If you only had two phases you
would get the big voltage drop that Iggy sees. Adding a cap won't help.

I don't know that it's looking at voltage; it may be pulse rate counting.
It's hard to tell from afar.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Feb 21, 12:33*am, Ignoramus19266 ignoramus19...@NOSPAM.
19266.invalid wrote:
I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

If this is true, that there's no filtering on the output of this
rectifier, you would see 360Hz ripple from it. It's entirely possible
that the ripple frequency is monitored. Take a look at the input
circuit on the next board. Chances are that there is a voltage divider
that brings the voltage down to something like 5 volts. Ig that's the
case, maybe you could disconnect this rectifier and replace it with a
360Hz oscillator. That would cost something less than $0.50. Or, if
this is going into the input of a missing pulse detector, maybe you
could just fake the output of the detector.

HTH

I'd agree. Depends on how much processing time the internal micro has.
Less cycles to read an A-D converter and do a compare less than, rather
than counting and timing.

David Lesher wrote:
RoyJ writes:

If I were designing that circuit, I'd put a resister in front of each
diode pair,and one behind the output. If you only had two phases you
would get the big voltage drop that Iggy sees. Adding a cap won't help.

I don't know that it's looking at voltage; it may be pulse rate counting.
It's hard to tell from afar.

Jim Wilkins wrote:

Wes, most meters read Average and scale it to the equivalent RMS
value. If they read RMS they'll say so.

I've always owned Flukes. No idea about the harbor fright stuff.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On Sat, 21 Feb 2009 23:32:04 -0500, Wes wrote:

Jim Wilkins wrote:

Wes, most meters read Average and scale it to the equivalent RMS
value. If they read RMS they'll say so.

I've always owned Flukes. No idea about the harbor fright stuff.

Wes

The issue is whether or not the measured waveform is sinusoidal or
something else. The ratio between RMS and avg value of rectified AC
is known for sine waves. True RMS for non-sinusoidal waveforms
requires either using heating value or circuitry to do the math.

On Feb 21, 8:36*pm, RangersSuck wrote:
On Feb 21, 12:33*am, Ignoramus19266 ignoramus19...@NOSPAM.



19266.invalid wrote:
I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

If this is true, that there's no filtering on the output of this
rectifier, you would see 360Hz ripple from it. It's entirely possible
that the ripple frequency is monitored. Take a look at the input
circuit on the next board. Chances are that there is a voltage divider
that brings the voltage down to something like 5 volts. If that's the
case, maybe you could disconnect this rectifier and replace it with a
360Hz oscillator. That would cost something less than $0.50. Or, if
this is going into the input of a missing pulse detector, maybe you
could just fake the output of the detector.

HTH

Yikes - I just realized that Iggy, who blocks posts from Google
Groups, will never see this. I really don't have the time or
inclination to change news readers right now (I've been down that road
before - I ran a major usenet feed in the early 90s), so if someone
wanted to forward this to Iggy...

Don Foreman wrote:
The issue is whether or not the measured waveform is sinusoidal or
something else. The ratio between RMS and avg value of rectified AC
is known for sine waves. True RMS for non-sinusoidal waveforms
requires either using heating value or circuitry to do the math.

I'm violating one of my rules here "reading and responding to an
electronic thread". :-)
But it's interesting that so many folks don't seen to understand
that point. The read what is on the front panel and "assume". :-)
...lew...

Don Foreman wrote:

On Sat, 21 Feb 2009 23:32:04 -0500, Wes wrote:

Jim Wilkins wrote:

Wes, most meters read Average and scale it to the equivalent RMS
value. If they read RMS they'll say so.

I've always owned Flukes. No idea about the harbor fright stuff.

Wes

The issue is whether or not the measured waveform is sinusoidal or
something else. The ratio between RMS and avg value of rectified AC
is known for sine waves. True RMS for non-sinusoidal waveforms
requires either using heating value or circuitry to do the math.

I guess you are saying most people don't have true rms meters which is what Jim is saying.

My 117 is true rms if I can believe the spec sheet, I'm pretty sure the meter I had before
it was also. Wish I had it here, I could generate some sine, square, and triangle waves,
measure them with the scope and then compare to what the meter indicates. That is subject
to a scaling factor of .707 or .577 .

Just to make sure I'm on the right track, 10 Vdc and 10VAC rms has the same heating value?

Average is a series of equally spaced samples of magnitude divided by sample number.
RMS deals with P=E^2/R which an average does not.

I'm going to have to go out and snow blow. I wasn't planning on thinking too much before
noon today.

Wes

Wes

RangersSuck wrote:

On Feb 21, 8:36*pm, RangersSuck wrote:
On Feb 21, 12:33*am, Ignoramus19266 ignoramus19...@NOSPAM.



19266.invalid wrote:
I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

If this is true, that there's no filtering on the output of this
rectifier, you would see 360Hz ripple from it. It's entirely possible
that the ripple frequency is monitored. Take a look at the input
circuit on the next board. Chances are that there is a voltage divider
that brings the voltage down to something like 5 volts. If that's the
case, maybe you could disconnect this rectifier and replace it with a
360Hz oscillator. That would cost something less than $0.50. Or, if
this is going into the input of a missing pulse detector, maybe you
could just fake the output of the detector.

HTH

Yikes - I just realized that Iggy, who blocks posts from Google
Groups, will never see this. I really don't have the time or
inclination to change news readers right now (I've been down that road
before - I ran a major usenet feed in the early 90s), so if someone
wanted to forward this to Iggy...

Done

On 2009-02-22, Wes wrote:
RangersSuck wrote:

On Feb 21, 8:36?pm, RangersSuck wrote:
On Feb 21, 12:33?am, Ignoramus19266 ignoramus19...@NOSPAM.



19266.invalid wrote:
I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

If this is true, that there's no filtering on the output of this
rectifier, you would see 360Hz ripple from it. It's entirely possible
that the ripple frequency is monitored. Take a look at the input
circuit on the next board. Chances are that there is a voltage divider
that brings the voltage down to something like 5 volts. If that's the
case, maybe you could disconnect this rectifier and replace it with a
360Hz oscillator. That would cost something less than $0.50. Or, if
this is going into the input of a missing pulse detector, maybe you
could just fake the output of the detector.

HTH

Yikes - I just realized that Iggy, who blocks posts from Google
Groups, will never see this. I really don't have the time or
inclination to change news readers right now (I've been down that road
before - I ran a major usenet feed in the early 90s), so if someone
wanted to forward this to Iggy...

Done

I unblocked RangersSuck, it is not that I block GG because I do not
like it, only because spammers post through it. Thanks a lot for a
good thinking on this measuring question.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Wes writes:


Just to make sure I'm on the right track, 10 Vdc and 10VAC rms has the same heating value?

Yes.


Average is a series of equally spaced samples of magnitude divided by sample number.
RMS deals with P=E^2/R which an average does not.

First off, the average value of a AC sine wave is.... zero.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Feb 22, 1:17*pm, Ignoramus13847 ignoramus13...@NOSPAM.
13847.invalid wrote:
On 2009-02-22, Wes wrote:



RangersSuck wrote:

On Feb 21, 8:36?pm, RangersSuck wrote:
On Feb 21, 12:33?am, Ignoramus19266 ignoramus19...@NOSPAM.

19266.invalid wrote:
I did a very extensive investigation of this. I opened this drive and
basically took it apart, board by board (while keeping notes as to
what is plugged to what).

What I found out is that there is a separate (from DC bus) phase loss
detection circuit. At least that is what I think.

The three wires connected to L1, L2, and L3 directly, are connected to
a tiny separate three phase rectifier (made of six little diodes), and
the output of that rectifier is fed into another board. There is no
capacitor at all in this circuit. I cannot think of any purpose of
this circuit, other than phase loss detection.

Therefore, simplistically, it would seem that adding a little
capacitor to this circuit may stabilize voltage there and fool the
board into thinking that all three phases are present.

Any thoughts on this?

i

If this is true, that there's no filtering on the output of this
rectifier, you would see 360Hz ripple from it. It's entirely possible
that the ripple frequency is monitored. Take a look at the input
circuit on the next board. Chances are that there is a voltage divider
that brings the voltage down to something like 5 volts. If that's the
case, maybe you could disconnect this rectifier and replace it with a
360Hz oscillator. That would cost something less than $0.50. Or, if
this is going into the input of a missing pulse detector, maybe you
could just fake the output of the detector.

HTH

Yikes - I just realized that Iggy, who blocks posts from Google
Groups, will never see this. I really don't have the time or
inclination to change news readers right now (I've been down that road
before - I ran a major usenet feed in the early 90s), so if someone
wanted to forward this to Iggy...

Done

I unblocked RangersSuck, it is not that I block GG because I do not
like it, only because spammers post through it. Thanks a lot for a
good thinking on this measuring question.

--
* *Due to extreme spam originating from Google Groups, and their inattention
* * * to spammers, I and many others block all articles originating
* * * *from Google Groups. If you want your postings to be seen by
* * * * *more readers you will need to find a different means of
* * * * * * * * * * * *posting on Usenet.
* * * * * * * * * *http://improve-usenet.org/

Understood. (and thanks, Wes). Getting a better new reader is
somewhere on my list of things to do, but Google Groups is just so
damned convenient.

Anyway, I'd be real interested in hearing how this missing phase
detector works out.
RS

David Lesher wrote:

First off, the average value of a AC sine wave is.... zero.

Okay, average of the absolute value

Lew Hartswick wrote:

I'm violating one of my rules here "reading and responding to an
electronic thread". :-)

It is starting to sound like a good rule for me too.

Wes

On 2009-02-22, RangersSuck wrote:

Understood. (and thanks, Wes). Getting a better new reader is
somewhere on my list of things to do, but Google Groups is just so
damned convenient.

Anyway, I'd be real interested in hearing how this missing phase
detector works out.

I will post an update once I figure out the safest way to do it. Which
could be some weeks away. For now I just wired it with three phase and
will work on the drive at my leisure.

Again, I have nothing personal against GG users. Only against
buy-my-counterfeit-shoes-and-handbags.com spammers.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

On Feb 22, 1:25*am, Don Foreman wrote:
...True RMS for non-sinusoidal waveforms
requires either using heating value or circuitry to do the math.

Like this:
http://www.analog.com/en/other/rms-t...s/product.html

I have some RF ammeters - they are nice - 4 wire thermocouple...
Heating effect of a precision coil drives the meter.

It works on DC to RF. Kinda nice military grade meters.
(I mean panel meter - not a hand or bench ones.) I have those in Mil
grade and in TI grade. My Beckman lost the LCD so I did the same to it.

Martin

Don Foreman wrote:
On Sat, 21 Feb 2009 23:32:04 -0500, Wes wrote:

Jim Wilkins wrote:

Wes, most meters read Average and scale it to the equivalent RMS
value. If they read RMS they'll say so.
I've always owned Flukes. No idea about the harbor fright stuff.

Wes

The issue is whether or not the measured waveform is sinusoidal or
something else. The ratio between RMS and avg value of rectified AC
is known for sine waves. True RMS for non-sinusoidal waveforms
requires either using heating value or circuitry to do the math.