2/03/2011

Digitrip 1150 Rating Plug

Article by: cpswitchgear.com

The following is the process to change out the overcurrent rating plug in an Eaton/Cutler Hammer Digitrip 1150 and 520 family of Power Circuit Breaker Trip Units. I will explain below the process, but first I want to make sure you remember a few basic steps before inserting a new rating plug. I will also talk a little about the operation of the current transformers.

Let's say for instance the tap is rated at 600 amps. If the circuit breaker is set up properly, the current transformers ( CT's )on each phase will also be 600 amps. Always check the current transformers before changing and inserting a new tap into the relay. A 1200 amp tap will fit into the same relay, but the breaker will not trip on the overcurrent settings as designed. ***** Never energize any circuit breaker without the overcurrent device attached. Damage to the internal CT's may occur because the circuit is now open, making for no protection for the load circuit.

Now to insert the rating plug, push it into the cavity on the right-hand side of the trip unit. There are three pins that need to be aligned on the plug with the sockets in the opening. Insert the plug with minimal force and the rating plug is now inserted and ready for testing. The overcurrent relay can be tested either by primary, or secondary injection. The power relay module is a standard accessory that will power up trip unit module for testing purposes.

For more information, please visit www.cpswitchgear.com or call Carolina Precision Switchgear at 704-596-4242.