how to measure amps on 4160V motor

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emiller233

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pittsburgh, pa
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Controls-Automation engineer
how do you go about measuring amps on 4160V motor? 200HP

We've obviously never dealt with it before. and our customer wants amp readings at various times while running the pump. they also want calibration certificates on the measuring equipment

We're renting a generator to run these motors in our shop during testing as we only have 480V. And they're handling all of the wiring for us as well. It will just have a pendant for start/stop for us to use for testing.
 
emiller233 said:
how do you go about measuring amps on 4160V motor? 200HP

We've obviously never dealt with it before. and our customer wants amp readings at various times while running the pump. they also want calibration certificates on the measuring equipment

We're renting a generator to run these motors in our shop during testing as we only have 480V. And they're handling all of the wiring for us as well. It will just have a pendant for start/stop for us to use for testing.
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Have an electrician install a power meter. Install a Current Transformer and a Voltage transformer to measure all electrical parameters of your 4160 motor. You can even communicate the reading in your computer.
 
emiller233 said:
how do you go about measuring amps on 4160V motor? 200HP

We've obviously never dealt with it before. and our customer wants amp readings at various times while running the pump. they also want calibration certificates on the measuring equipment.
Click to expand...

You've a pretty good answer on the amps; he even included the additional capability for power, which I'd say is probably important.

OK ... this drives a pump ... and you say "amp readings at various times while running the pump" which suggests at varying loads. So ... are also needing calibrated flow and pressure instrumentation? Pressure is likely readily available; flow MAY be, but may not be.

You really need to get the test procedure from your customer's engineering department. Be VERY WARY of a verbal test procedure through a sales and/or purchasing department. I've seen many bitten by them.
 
bobby ocampo said:
Have an electrician install a power meter. Install a Current Transformer and a Voltage transformer to measure all electrical parameters of your 4160 motor. You can even communicate the reading in your computer.
Click to expand...
Agreed. We Grossen Metrawatt power analysers in our MV panels.
 
GeorgeB said:
You've a pretty good answer on the amps; he even included the additional capability for power, which I'd say is probably important.

OK ... this drives a pump ... and you say "amp readings at various times while running the pump" which suggests at varying loads. So ... are also needing calibrated flow and pressure instrumentation? Pressure is likely readily available; flow MAY be, but may not be.

You really need to get the test procedure from your customer's engineering department. Be VERY WARY of a verbal test procedure through a sales and/or purchasing department. I've seen many bitten by them.
Click to expand...

Yes, this is in a hydraulic power unit going into a nuclear plant. We have all of those transmitters abd more on the HPU itself. 3 of each actually (best of 3 logic on everything). So we're good there. We do have their test procedures. They want amp readings from each leg of each motor, at certain PSI/GPM combinations. The load varies but readings will be at several predetermined set points through the pumps range. we can control both the pressure and flow inside the pump from the laptop.
 
Besoeker3 said:
Agreed. We Grossen Metrawatt power analysers in our MV panels.
Click to expand...

These look like they would work, just trying to think how I'd get the sensors into the motor doghouse. Is there any issues having them in there?

We aren't allowed to hook up on the generator side of the cables...
 
emiller233 said:
These look like they would work, just trying to think how I'd get the sensors into the motor doghouse. Is there any issues having them in there?

We aren't allowed to hook up on the generator side of the cables...
Click to expand...
No issues that I'm aware of. But being from UK we don't work with the NEC.
 
emiller233 said:
These look like they would work, just trying to think how I'd get the sensors into the motor doghouse. Is there any issues having them in there?

We aren't allowed to hook up on the generator side of the cables...
Click to expand...

I would argue that you'd want to keep any current transformers or probes away from the immediate vicinity of the motor's magnetic fields for the best accuracy. Perhaps you could use that line of reasoning to justify a separate panel between the generator and motor for doing the measurements. A steel panel provides magnetic as well as electrostatic shielding.
 
synchro said:
I would argue that you'd want to keep any current transformers or probes away from the immediate vicinity of the motor's magnetic fields for the best accuracy. Perhaps you could use that line of reasoning to justify a separate panel between the generator and motor for doing the measurements. A steel panel provides magnetic as well as electrostatic shielding.
Click to expand...

Any space restrictions? Can they cut the wires and splice them inside of this box, or would we need some kind of lugs to land each of them on?
 
A wraparound current transducer coil (Rogowski coil) has all sorts of potential advantages for a situation like this. No need to disturb the wire, no bulky split core current transformer to add to the untouched wire.
 
emiller233 said:
You can put these in the motor doghouse?
What's the output signal on these
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The downside is that the voltage output signal at high impedance has to go through an amplifier processor circuit. I do not recall the exact nature of the output signal.

Sent from my XT1585 using Tapatalk
 
GoldDigger said:
The downside is that the voltage output signal at high impedance has to go through an amplifier processor circuit. I do not recall the exact nature of the output signal.
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Yep, high impedance.
The ones I have seen are 150 mv at rated load and output is not linear with current.

But, they worked great and were close enough for us.

I've seen readouts allowing tailoring the output curve to account for the non-linearity -but I have never worked any
 
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