FIELD APPLICATION RELAY FOR SYNCHRONOUS MOTOR

[obut4]

Hi,

I ‘am looking for a “field application relay” (ANSI code 56) for synchronous motor with static excitation system.
The motor is a synchronous brush type motor of about 10MW with Direct Online Start.

The field is shorted with a resistor connected across the field at the start. The field application relay senses voltage and frequency across this resistor. The frequency is 50 Hz at the beginning and drops towards zero as the motor reaches synchronous speed (same for the voltage). When the motor reaches about 95% speed the field is applied and current is injected in the rotor winding.

I know that the relay SPM from GE has the field application function but it is very expensive.
I ‘am looking for an alternative solution based on the measurement of voltage and frequency across the starting resistor.

Thanks for your advices,

 

[waross]

These were originally called "Polarized Field Frequency Relays".
These people held the original patent on the "Polarized Field Frequency Relay".
They no longer list the PFFR on their web site but it is probably worth a phone call to them.
Note that relay acts not only on frequency but also on phase angle to avoid exciting out of sync.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[obut4]

Thanks Waross, I did not know it is called a PFFR.
The thread 237-230415 is also speaking about it.

Does any have example of PFFR that i could used?

Thanks for your help

 

[obut4]

Hi,

If anyone is interested i have found two suppliers for synchronous motor field application relay:

- GE: with the relay C2820C100, but it is impossible to find somebody who would sll this relay inside GE.

- Lenoir Elec (a french company): relay RBC 1054 ZB

Obut4