3 phase motor protection

[gewali]

I've a 3 three phase motor and i need to run the motor over 400 volts. if the volatge level falls below 400V , it need to be off. how can I do that?

 

[brushhead]

Use a voltage sensing relay and a contactor?....simple but effective.

 

[gewali]

Use a voltage sensing relay and a contactor?....simple but effective.

I think relay is not much reliable, can you suggest me alternatives?

 

[brushhead]

How reliable do you need it to be? Ok perhaps three small 230V transformers wired in star, with a rectifier on the other side, and a comparator compared to a known reference, and then drive a contractor to drop out the motor, or disable an AC drive that would be running the motor? Most AC drives would allow you to drive in an analogue input 0-10V with a small PLC type program running on the drive. Input volts below a certain level; disable the drive output.

 

[gewali]

How reliable do you need it to be? Ok perhaps three small 230V transformers wired in star, with a rectifier on the other side, and a comparator compared to a known reference, and then drive a contractor to drop out the motor, or disable an AC drive that would be running the motor? Most AC drives would allow you to drive in an analogue input 0-10V with a small PLC type program running on the drive. Input volts below a certain level; disable the drive output.

Realibity is the major concern, I was thinking the same, would that be enough to protect the motor, what extra factor i need to add, to make the motor more protected.

 

[FvM]

Normally, a correctly dimensioned motor circuit breaker or overcurren relay gives suffcient and reliable protection against all kinds of overloads and voltage failure. It's not obvious why it should not be sufficient for your application.

 

[gewali]

Normally, a correctly dimensioned motor circuit breaker or overcurren relay gives suffcient and reliable protection against all kinds of overloads and voltage failure. It's not obvious why it should not be sufficient for your application.

Relays establishes the connection again when it bounce back, so I generally do not prefer i

 

[FvM]

Relays establishes the connection again when it bounce back, so I generally do not prefer i

Industry standard overcurrent relays need a manual reset once they have tripped (the same with MCBs).