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How to determine the running state of Synchronous motor?

How to determine the running state of Synchronous motor?

How to determine the running state of Synchronous motor?

(OP)
Friends,
Greetings!
I'm trying to determine the running state logic of Synchronous Motor. I don't have field contactor breaker status and speed signal.
The signals I have are stator current, 52A stator breaker status, rotor field current, rotor field voltage.

This machine is started as Induction Motor (I have running state logic for this motor).
I'm thinking of something like below:
positive sequence current > mininmum full load Amp
Field current (from DCCT) > ? (I don't know how much this should be)
Field voltage (from voltage divider circuit) > ? (I don't know how much this should be)
A  delay timer

This is for general application and not specific to a machine.


Please share your inputs on how much field current, field voltage should be, also suggest me If I need more inputs to determine the running state of synchronous motor.

Thanks,

RE: How to determine the running state of Synchronous motor?

The induced voltage in the rotor winding says a lot. The frequency is same as grid frequency when you start.

As the motor is gaining speed, the rotor winding voltage frequency gets lower and lower and you may use that frequency to initiate DC excitation.

It may be a good idea to overexcitate somewhat to lock the rotor in. Then go back to cos(phi) or voltage or power control or what you cose to control.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: How to determine the running state of Synchronous motor?

Not sure why you are doing this but if it is for any type of protection then there are transient conditions to consider. You should put some thought into detecting a slipped pole, both during synchronizing and during running while synchronized.

The required level of the field current depends on the motor load. You need to consider the operating range oif you are going to do any power factor regulation or allow the operators to adjust the DC. The field voltage does not matter much - if you have the necessary current then you must have the required voltage.
 

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