Contactor Performance during fault
Contactor Performance during fault
(OP)
Hi,Guys,
I am dealing with One medium voltage starter company.I don't want to mention its name.
This company chose a fuse-contactor combination and our senior enginner approved it. But later on, after I did short circuit calculation, i realized that fuses can't well protect the contactors. What would happen is, during the fault, the contactors will open itself because of voltage dip on its coils before the contactors can clear the fault(The fuses are too big), meaning the contactors would have to interrupt the fault above its interrupting capacity. It is very dengerous.
But that senior guy and the manufactuer insisted on their doings. His argument is, the manufactuer deigned the fuse-contactor- starter for the motor protection. Therefore, their contactors will be well protected, because this is a international company, they cann't make this kind of mistakes.. But how could they choose the fuses without knowing the fault levels?
I got so frustrated about what they are doing.
I would appreciate it if somebody can direct me to a right way to deal with them. Should I quit or live with it?
I am dealing with One medium voltage starter company.I don't want to mention its name.
This company chose a fuse-contactor combination and our senior enginner approved it. But later on, after I did short circuit calculation, i realized that fuses can't well protect the contactors. What would happen is, during the fault, the contactors will open itself because of voltage dip on its coils before the contactors can clear the fault(The fuses are too big), meaning the contactors would have to interrupt the fault above its interrupting capacity. It is very dengerous.
But that senior guy and the manufactuer insisted on their doings. His argument is, the manufactuer deigned the fuse-contactor- starter for the motor protection. Therefore, their contactors will be well protected, because this is a international company, they cann't make this kind of mistakes.. But how could they choose the fuses without knowing the fault levels?
I got so frustrated about what they are doing.
I would appreciate it if somebody can direct me to a right way to deal with them. Should I quit or live with it?






RE: Contactor Performance during fault
Are you sure you are correct in your findings as it is most unlikely that the switchgear supplier can get the fuse size incorrect.
You could also present/ send your findings to the supplier for his comments and if you are correct then he should be grateful.
RE: Contactor Performance during fault
You could just go directly to the manufacturer with your findings and confirm your findings with them. After all, the fuse/contactor co-ordination is part of the fault study so contacting the manufacturer to confirm your findings is part of that study.
Oh, just being a big company doesn't make them immune from making mistakes.
RE: Contactor Performance during fault
RE: Contactor Performance during fault
In another case, we thought the fuse was too large because at the contactor's maximum rating of 6000 Amps, the fuse took some time to clear the fault. The manufacturer showed that the contactor drop out time was longer than the fuse clearing time. The contactor would never open during the high fault before the fuse blew.
RE: Contactor Performance during fault
GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata
RE: Contactor Performance during fault