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I am designing a panel and would like to include a main contactor that switches off the entire panel on pressing the emergency stop button.

There's an MCCB at this panel's input. However, I would like to include additional protection for the panel, that is, a fuse holder block but I am not sure whether to place this fuse holder between the MCCB and the main contactor or after the main contactor?

Please refer to the image below for a better context of this question. a sketch of the two input power design options that I have

Curiousone
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  • What specifically are you trying to protect with the fuse? – Andy aka Jun 27 '23 at 08:13
  • If you want fuses to add protection above that provided by the MCCB, then they should be matched to each of the devices supplied so a fuse for each device after the main contactor. – Solar Mike Jun 27 '23 at 09:11

1 Answers1

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Standard practice is to use busbar fuses ahead of the MCCB. They should be capable of handling a higher short-circuit current than the MCCB.

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Each branch circuit is protected by an MCB or, in the case of motors, MOCBs (motor protection circuit breakers) followed by a contactor.

A main contactor is not required to cut the power. The emergency-off pushbutton switch (that is part of the control circuit), when actuated, de-energises the 'control on' and other contactors to effectively shut down the equipment.

vu2nan
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