VFD Power Factor Angle

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I assume that means that it is giving you the angle between the real power and the apparent power.

So at an angle of zero, the PF has to be 1. And at an angle of 90 degrees, the PF has to be 0.

My math is a little rusty, but it has to be one of the trig functions. And the cosine is the only trig function that gives the correct answer for those two points.

So I'm guessing the PF = Cosine (Angle).

Edit: I haven't tried to google anything to verify if this is correct.
 
ptonsparky said:
My 12 year old AD GS2-23P0 vfd will give me the power Factor Angle. How do I convert that to Power Factor?
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There are essentially two different power factors. There is the input side of the VFD. Usually we made the input side 0.9 pf. For that you need the current essentially a 120 degree on the first cycle and -120 deg in the other half. The output of the VFD is variable PF depended load. If it is at full load it is typically 0.8 PF. We have had a few that were 8-pole motors and these were 0.70 PF or lower.

I don't know if that helps any.
 
steve66 said:
My math is a little rusty, but it has to be one of the trig functions. And the cosine is the only trig function that gives the correct answer for those two points.

So I'm guessing the PF = Cosine (Angle).
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That is for a linear function. VFDs are not linear.
 
Besoeker3 said:
That is for a linear function. VFDs are not linear.
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If we are talking about the power factor of the driven motor that is going to be linear or darn close to linear.

The rather inexpensive AD drives like OP has probably won't tell you much of anything about what is going on with the input leads. DC bus and beyond is all that they monitor or control. Only clues about input problems is if they cause DC bus voltage to drop too low.
 
kwired said:
If we are talking about the power factor of the driven motor that is going to be linear or darn close to linear.

The rather inexpensive AD drives like OP has probably won't tell you much of anything about what is going on with the input leads. DC bus and beyond is all that they monitor or control. Only clues about input problems is if they cause DC bus voltage to drop too low.
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For just the motor, yes. But how useful is that for the system voltage ?
 
Besoeker3 said:
For just the motor, yes. But how useful is that for the system voltage ?
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Is not. But the thing is like I said, with these lesser expensive drives there is nothing really monitoring anything on the input lines, just the DC bus and beyond. So nothing all that useful built into them for anything involving system voltage other than if something happens that causes a drop in DC bus voltage, but all that does is alert you the bus voltage is too low and you still need to figure out why. Bus overvoltage is one other somewhat common problem, is usually encountered when there was a blip in supply voltage while the motor was running and it was not able to successfully restart "on the fly".
 
kwired said:
Is not. But the thing is like I said, with these lesser expensive drives there is nothing really monitoring anything on the input lines, just the DC bus and beyond. So nothing all that useful built into them for anything involving system voltage other than if something happens that causes a drop in DC bus voltage, but all that does is alert you the bus voltage is too low and you still need to figure out why. Bus overvoltage is one other somewhat common problem, is usually encountered when there was a blip in supply voltage while the motor was running and it was not able to successfully restart "on the fly".
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I'm sure you are right. We did mostly industrial and everything was monitored.
 
The VFD can give me output current, voltage, and Power Factor Angle along with percentage of the drive rated power.
Using 2.7A, 103V, 31PFangle, and .77 efficiency I get about.338 KW and about .45 HP output on the motor.

The one thing that bothers me is the output voltage. The Drive says 103 volt but my fluke 87 says 164 volt. I'm missing something there.
Changes answer to.537 Kw and .72 Hp.)
 
I suspect that your Fluke 87 is trying to read the output voltage expecting it to be a sine wave. Likely advertised as a "true sine wave DMM".

The output of the VFD is anything but a sine wave. It's a chopped up (Pulse Width Modulated) version of the DC Bus+ and DC Bus -.

That series of crazy square waves have a lot of high frequency components that the (big bandwidth) DMM can respond to. And the DMM typically does show higher numbers because of this.

The output voltage displayed on the VFD is a "caculated" value meant to represent the voltage you'd read from the fundamental component of the drive's output (like 30Hz if running at half speed). Like if it really was a sine wave.
 
ptonsparky said:
The one thing that bothers me is the output voltage. The Drive says 103 volt but my fluke 87 says 164 volt. I'm missing something there.
Changes answer to.537 Kw and .72 Hp.)
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The drive shows the voltage of the fundamental sine wave component of the PWM output, which is the useful component for the motor. The Fluke 87 is likely responding to all of the high frequency components of the PWM waveform, and its RMS response is also likely overweighting the peaks of the switching noise. Therefore it will read much higher than the drive shows. There are meters that have a lowpass filter that can be engaged to make them more accurate for measuring VFD outputs.

Motor windings will be inductive, which makes the current through them proportional to the integral of the voltage, which ends up filtering out the high frequency switching noise. And so the level of that noise is not relevant to basic motor operation.

I see MD Automation just beat me to it!
 
Yes, the analog Simpson would give you a better indication on the output side of the drive. A digital meter on the output will not provide much useful information. The data provided by the drive itself will be better than either meter.
 
If you have the Fluke 87V model it has a low pass filter that should give you close to the value the drive is giving you. If you have older model like 87-III without filter, use the Simpson or another digital meter with low pass filter enabled if available.
 
dkarst said:
If you have the Fluke 87V model it has a low pass filter that should give you close to the value the drive is giving you. If you have older model like 87-III without filter, use the Simpson or another digital meter with low pass filter enabled if available.
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Older model 87s. I wish I still had the Simpson. It walked away.
I may try an old analog Amprobe if I can scrounge it up.
 
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