Compressor Tripped on E/F During Motor Starting Only

Short out the CTs during starting for a defined time with either the PLC/SCADA or a timing relay.

Not sure about what you have done so far--But, if your motor is good and you are faulting on start-up, take the overload out of the start-up by shorting the current transformers out for enough of the ramp time to skip the high inrush current.

Dear All,

If the interposing CT is bypassed, everthing will be still working fine in normal situation.

But when fault occured, CT secoundary current is high and the transducer can be damaged. Interposing CT is used to protect the transducer.

It is possible to change new transducer 3 element module instead of the old transducer and add one interposing CT (5VA 1:1) respectively.

Please advise.

Best regards,

Sittichai B.

EE

Dear All,

In this case, we can't separate the protection circuit and the metering circuit by to use another core of CT.

I ask vendor about this problem but there is no answer from him.

In my opinion, Can we disable function E/F (relay SPAC315C)?

When is motor starting?

Please advice

Best regards,

Sittichai B.

Electrical Engineer

I think that is what I tried to convey.

Take your start command to a timing relay and set it for enough time to avoid the inrush current--Wire the current transformers in parallel to normally open contacts that will short them together for time during starting.

After the timing relay times out, the contacts open and return the CTs to how they are wired now.

In short--Use a timing relay or a rung of logic with a timer that will close contacts and short the CTs for start up.

Should do it--Size them properly!