Motor starting calculation
Motor starting calculation
(OP)
I am doing motor startng study. I have two sets of data from motor manufacturer.One is motor circuit data, which is impedance data. The other is motor characteristic data, which is speed-torque curve. ETAP software accepts both. I am wondering which set of data is more accurate for the motor starting study.
I was told by a senior guy that I should use the speed-torque curve. But I personally think the motor circuit data is more accuarate for the study. Because the motor circuit data determine the speed-torque curve and speed-torque curve shape is based on defferent test conditions.
But I am not sure if my understanding is right. I have to convince that guy to accept my idea. Who have a better understanding of motor starting.
I apprecite it for your great idea.
I was told by a senior guy that I should use the speed-torque curve. But I personally think the motor circuit data is more accuarate for the study. Because the motor circuit data determine the speed-torque curve and speed-torque curve shape is based on defferent test conditions.
But I am not sure if my understanding is right. I have to convince that guy to accept my idea. Who have a better understanding of motor starting.
I apprecite it for your great idea.






RE: Motor starting calculation
All the calculation prg use more or less the same motor model. But only "more or less".
Starting from the measured values, that means voltages, currents, pf, torque, etc, you can obtain your model with some formulas. These aren't exactly the same in all books. For instance, some books reports the rotor resistance as a slip function.
Thus it is not sure that you can use the proposed model parameters in your prg obtaining the correct motor behaviour.
The aim of your study is to reproduce, to simulate the motor behaviour. So you should input the measured parameters and let your prg to reproduce them as better as possible.
RE: Motor starting calculation
RE: Motor starting calculation
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RE: Motor starting calculation
Equivalent circuit parameters are a little further removed from what you need. You can certainly calculate torque/speed and current speed from equivalent circuit parameters but then you have to make sure that the conventions your ETAP program uses are exactly the same as what the manufacturer is supplying you.
I think that by and large manufacturers estimate equivalent circuit parameters and derive torque speed curve from there. But there may be more to it than just that. Consider this fact:
You can not ever get a curve which has a local minimum between locked rotor torque and breakdown torque using the standard linear equivalent circuit. Yet many motor torque speed curves from the manufacturer have this feature. That leads me to believe there may sometimes be more than equivalent circuit parameters which goes into developing the torque speed curve.
Based on these factors I would be more comfortable using torque-speed and current speed directly rather than going to some more abstract equivalent circuit parameters and trying to infer the correct torque-speed and current-speed curves.
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