PowerFlex Drive on network using RSLogix5000

Mihir_007 · Mar 13, 2015

Greetings.

When using a powerflex drive on ethernet, with RSLogix5000,
Is there any drive tag which read the actual RPM of motor?

I have an application in which speed of motor is given in terms of RPM and actual speed feedback is also required in terms of RPM as well.

Request you to assist further.

rdrast · Mar 13, 2015

The Feedback and Reference tags are in whatever units are appropriate.
If you need more, you can configure any paramter (say, encoder RPM) to be sent to the PLC.

jraef · Mar 13, 2015

Mihir_007 said:
Greetings.

When using a powerflex drive on ethernet, with RSLogix5000,
Is there any drive tag which read the actual RPM of motor?

I have an application in which speed of motor is given in terms of RPM and actual speed feedback is also required in terms of RPM as well.

Request you to assist further.

If you do not have an encoder, resolver or tachometer on the motor shaft, the drive can only "guess" at the actual motor speed, however you can look at the COMMANDED speed and be +-5% in all likelihood. You don't state the purpose so no way to know what you are looking for here.

There are many different versions of PowerFlex drives, so that is not enough information in itself to take this any further. But SOME of them (PowerFlex 755) have an option for using Sensorless Flux Vector Control and in that operating mode, the drive is able to know the actual motor RPM because it is tracking that using internal sensors in order to do the vector algorithm calculations. It is not quite as accurate as using the encoder feedback, but only in orders of magnitude that may be irrelevant to your use, but here again insufficient information from you makes that a conjecture.

Mihir_007 · Mar 14, 2015

jraef said:
If you do not have an encoder, resolver or tachometer on the motor shaft, the drive can only "guess" at the actual motor speed, however you can look at the COMMANDED speed and be +-5% in all likelihood. You don't state the purpose so no way to know what you are looking for here.

There are many different versions of PowerFlex drives, so that is not enough information in itself to take this any further. But SOME of them (PowerFlex 755) have an option for using Sensorless Flux Vector Control and in that operating mode, the drive is able to know the actual motor RPM because it is tracking that using internal sensors in order to do the vector algorithm calculations. It is not quite as accurate as using the encoder feedback, but only in orders of magnitude that may be irrelevant to your use, but here again insufficient information from you makes that a conjecture.

Got it.

I just want to show RPM of motor without putting any encoder so Shall i scale a frequency with respect to RPM?

i.e.,

Let us say, Motor nameplate has maximum 1500 RPM and maximum frequency set as 50Hz. So shall i scale frequency (0-50Hz) with respect to RPM(0-1500)?
shall i be able to figure out the RPM from this?

I know this will not be the actual RPM but i may have a rough idea from this.

NetNathan · Mar 16, 2015

Mihir_007 said:
Got it.

Let us say, Motor nameplate has maximum 1500 RPM and maximum frequency set as 50Hz. So shall i scale frequency (0-50Hz) with respect to RPM(0-1500)?
shall i be able to figure out the RPM from this?

I know this will not be the actual RPM but i may have a rough idea from this.

This should work okay, since (in this use) rpm is almost directly related to frequency.
On rapid or large changes in speed (frequency) it may be off while the motor catches up to the frequency.

VictorBit · Mar 16, 2015

For estimate

For estimate:
____________________________________
Srpm: synchronus revolutions per minute
C(constant): 120'
F: Supply Frequency
P: Pole Numbers of the motor
____________________________________

Srpm=((120xF)/P),

Example, a inducation motor running on 35Hz (4pole);

Srpm=((120x35)/4) :1050 rpm

____________________________________

PowerFlex Drive on network using RSLogix5000

Mihir_007

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rdrast

Lifetime Supporting Member

jraef

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Mihir_007

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NetNathan

Lifetime Supporting Member

VictorBit

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