20hp motor Ground Fault Protection

[burntcoil]

We have some critical 20hp motors. The motor starters have a MCP (motor circuit protector), NEMA Contactor and bi-metallic overload relay without any ground fault protection. I want to change the bimetallic overload relay with electronic overload relay that comes with ground/jam protection module.
The problem is in case of ground fault, the new ground fault module, how it will trip the motor? Can I open the contactor under ground fault? What is the optimum solution?

 

[ScottyUK]

Can you fit a shunt trip to the MCP?

 

[jraef]

Yes, a solid state OL relay with GFP will simply open the contact on the OL relay to drop out the contactor if the SSOL detects a ground fault, typically via the Residual Current Detection method. The only difference is that the GFP will not wait for a time/current curve to be exceeded, it trips as soon as the GF is detected.

Are you thinking Ground Fault Protection in an SSOL is the same as a GFCI used to protect people from shock? Because if so, you are incorrect. Anything you get for a 3 phase motor will be Ground Fault Protection for EQUIPMENT only. It's not the same.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[burntcoil]

I want to use it to protect the motor. Since these protections are pretty sensitive so as per my understanding the fault will not wait to reach to a level of actual ground fault but will trip on some percentage of FLA unbalance. I will be using AB E3 or E1 plus relay with Jam/Ground Fault module. I just want to make sure its safe to drop a contactor under such condition using OL relay contact.

 

[jraef]

Yes, that's what those are designed to do. It's not a problem for the contactor.

Unless you are using DeviceNet, don't use an E3, use the new E300 instead. The E3 is moving to the status of being sold for replacement purposes now that the E300 is fleshed out (other than the DeviceNet interface for it not being ready yet).


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[GroovyGuy]

Howdy BurntCoil,
Is your power system solidly grounded, ungrounded, or (preferably) hi-resistance grounded?
GG

I am forever learning and changing.
W.E. Deming