IEC LV MCCs - Withdrawable starter units

[NickParker]

All outgoing units shall be executed as fully withdrawable units complete with test facilities, i.e. all connections to vertical busbars and outgoing power and control cables shall be via plug/sockets/sliding contacts and no (test supply) disconnections are required when the unit is to be put into the test position.

Is it the the control power disconnection when in test position? It is common to provide separate control power when the starter unit (withdrawable unit) is in Test position
What is the intention of this clause?

 

[che12345]

I may had misunderstood your question.
1. I had fabricated thousands of LV withdrawable system. It is standard design/practice that no (test supply) disconnections are required when the unit is to be put into the test position.
In test position:
a) the main power contacts shall be disconnected.
b) the test supply is still connected via a longer sliding contact or other arrangements.
c) the ACB, MCCB, contactor, starter etc., shall be able to be "tested" (closing/opening , full function etc.), but with the main power contacts "disconnected" from the main busbars.
2. Only in "disconnected" position, both the main power contacts and the test supply connections are disconnected.
Che Kuan Yau (Singapore)

 

[NickParker]

Hello Mr. Che Kuan Yau,
Thank you for your response!
After discussing with my client, I confirmed that the clause "no (test supply) disconnections are required when the unit is in the test position" applies to certain vendors who are unable to provide a separate control power (via the sliding contacts) for the motor space heater when the starter bucket is in the test position.