measuring motor efficiency
measuring motor efficiency
(OP)
Hi,
I'd like to test thyristor based motor controller (measuring voltage zero crossing to regulate the current flow) on the on 3 phase induction motor. What would be appropriate equipment and what electrical and mechanical parameters I have to measure to obtein the most reliable assess of efficiency and possible savings. Please, recommend some non-costly meter or device. The motor 37kW is in the field and I would like to find some less intrusive but still reliable method.
I'd like to test thyristor based motor controller (measuring voltage zero crossing to regulate the current flow) on the on 3 phase induction motor. What would be appropriate equipment and what electrical and mechanical parameters I have to measure to obtein the most reliable assess of efficiency and possible savings. Please, recommend some non-costly meter or device. The motor 37kW is in the field and I would like to find some less intrusive but still reliable method.





RE: measuring motor efficiency
There is no simplistic method for making such a determination. You will have to spend the $$$$$$$$$ to obtain the necessary equipment.
First you need to measure the power into the motor at the fundamental frequency... that is, the Watts input.
Next you need to measure the mechanical power out of the motor and that is done with a dynamometer... with a torque sensor to measure the shaft torque and speed...that runs in the neighborhood of >$10+ K .... not incuding the instrumentation etc....
RE: measuring motor efficiency
RE: measuring motor efficiency
http://www.voltech.com/products/pwr_anl/index.htm
- but even this will cost perhaps US$2000. You will also need three CT's (current transducers) of adequate current rating and frequency response to use with the analyzer, these won't cost that much, see:
http://www.lem.com/
More difficult is the torque measurement. JOmega is right, I don't think this will be cheap or easy to apply in the field.
RE: measuring motor efficiency
RE: measuring motor efficiency
Can't help with torque measurement, other than to suggest that one of the universities might have a dynamometer rig which you could rent time on.
RE: measuring motor efficiency
A watt meter can be used to measure input although we have used more sophistated instrumentation.
Results appear to be accurate to around 99%.
Obviously if you know the electrical input and the mechanical output the efficiency is calculable.
In addition to efficiency studies, I have used this equipment to determine the output of a diesel engine in order to size a replacement electric motor. Also if your equipment is fast enough with a high sampling rate you can see a torque sine wave or determine locked rotor torque useful for estimating inertia.
You can isolate electrical vs. mechanical issues, like where the gearbox guy says it's not his fault and the motor guy says the motor is OK.
When one knows the torque the answer becomes obvious.
RE: measuring motor efficiency
Two quick questions:
1 - Do you know if they publish the accuracy?
2 - How is imbalance addressed? Is there a counterweight on other side of the shat?
RE: measuring motor efficiency
RE: measuring motor efficiency
RE: measuring motor efficiency
RE: measuring motor efficiency
there should be formula from motor manufacturer
that shows heat exhange dependance ( motor T, air flow speed, ambient Temp.).
All effectiveness questions coming to
ratio: what portion of cosumed active energy coming to heat.
If you have active energy reading and calculated
heat dissipation, then efficiency is available.
Thanks,
Vladimir.
RE: measuring motor efficiency
Thread237-56540
Note the links to MarkE's page... he has some very good info on it.
We have discussed it appears sometimes the claims of these devices are hyped up beyond realistically-achievable gains. The most benefit is possible for smaller motors which are typically inefficient. And the gains only occur when the motors are lightly loaded.
RE: measuring motor efficiency
RE: measuring motor efficiency
heat dissipation, then efficiency is available.
How to calculate the savings?
RE: measuring motor efficiency
Active energy readings available from on board watt meter (useful energy plus losses), losses as heat dissipation available using thermal dissipation model from manufacturer:
heat loss in watts as function from ambient T, rpm .
Thanks,
Vladimir.
RE: measuring motor efficiency
I'd like to test thyristor based motor controller (measuring voltage zero crossing to regulate the current flow) on the on 3 phase induction motor. What would be appropriate equipment and what electrical and mechanical parameters I have to measure to obtein the most reliable assess of efficiency and possible savings.
///Please, are you interested in the motor controller efficiency measurement or as the title reads "measuring motor efficiency" implying the interest in the motor efficiency, or both? Considering the motor efficiencies, these are usually available from the motor nameplate and from the motor manufacturers.\\\
Please, recommend some non-costly meter or device.
///Please, clarify meter or device for what purpose.\\\
The motor 37kW is in the field and I would like to find some less intrusive but still reliable method.
///Please, would you clarify for what that method is supposed to be?\\\
///
RE: measuring motor efficiency
RE: measuring motor efficiency
RE: measuring motor efficiency
If the voltage and current waves are undistorted, then
Wattmeter reading on the drive input Wdrive,input might be measured, and Wdrive,output might be measured. Then, the drive efficiency would be EFFdrive=Wdrive,output/Wdrive,input.
If the waveforms are distorted by harmonics, which is probably the case, then the input current and voltage and output current and voltage need to be rectified and filtered to be then measured by dc ammeter and voltmeter.
The motor Wmotor,input=Wdrive,output
and the Wmotor,output can be obtained via a dynamometer measurement of HP.
Then, EFFmotor=Wmotor,output/Wmotor,input