CBCT spurious tripping
CBCT spurious tripping
(OP)
here is the case
PCC feeding 1 MCC and 1 VFD MCC.
Seq of events
1.MCC motor on DOL running fine.
2.one of the vfd motor start in the VFD mcc.
3.We are facing spurious tripping of few DOL LT motors (conected to MCC )having CBCT wired with 3RB relays.
please help me why is this happening and also please give me solution or this...
PCC feeding 1 MCC and 1 VFD MCC.
Seq of events
1.MCC motor on DOL running fine.
2.one of the vfd motor start in the VFD mcc.
3.We are facing spurious tripping of few DOL LT motors (conected to MCC )having CBCT wired with 3RB relays.
please help me why is this happening and also please give me solution or this...






RE: CBCT spurious tripping
This is a common problem and worth checking out.
RE: CBCT spurious tripping
RE: CBCT spurious tripping
What is a CBCT? (Circuit Breaker Currnt Transformer?)
Waht is a 3RB relay?
I assume an "LT" motor is a "Low Tension" or low voltage motor and "DOL" is direct across the line motor starting or FVNR (Full Voltage Non Reversing) in NEMA/ANSI world.
With a little more information, we might be able to suggest some issues to look at.
RE: CBCT spurious tripping
RE: CBCT spurious tripping
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If we learn from our mistakes I'm getting a great education!
RE: CBCT spurious tripping
RE: CBCT spurious tripping
RE: CBCT spurious tripping
RE: CBCT spurious tripping
What do you find in the relay manual! With some relays, you may have to use custom made CBCTs. See the requirements for CBCT in the relay literature and compare with the name plate of the CBCT that is installed. You may get some clue. It may help if you can post the relay manual on the site so that others can have a look at it too.
RE: CBCT spurious tripping
The 3RB12 electronic overload relay is suitable for frequencies of 50/60 Hz and their related harmonics. The manual says it's possible to use the 3RB12 on the line side of a frequency converter. Please verify also if the core balance CT you used is the one recommended by 3RB12 manual, as raghun said.