Operational Leakage Current from Servo Drives

[dmac123]

Dear Electric Power and Transmission Forum:

As part of our HILS testing we are operating 4 Bosch HCS01 servo drives (24VDC for control, 230VAC single phase for motor supply)and their corresponding AC motors in an office-type environment.
The earth leakage in the office has a trip sensitivity of 30 mA.
The operation of all the drives results in frequent trips of the earth leakage which needs to be resolved so we can continue with our development.
I have not measured the magnitude of the leakage current since we do not have the required equipment.

From what I understand we should have a type B RCBO breaker with a higher trip sensitivity, presumably around 300mA, which will help minimize or eliminate the trips. However, presumably those levels of current could be dangerous to personnel? If so is there a way to handle the operational leakage current without increasing the trip sensitivity? I have heard of people using UPS's, where the 230VAC supply to the drives runs via a UPS but I'm not sure if this is a viable option?

Any suggestions would be greatly appreciated.

David

 

[waross]

Is it possible to split your loads into two circuits, each protected by a 30 mA class breaker?
That would maintain your 30 mA protection and probably avoid the trips.
Before changing circuits, however, check that none of the motor units is developing excess leakage current.
No test equipment?
Try running in groups of three, with a different motor out on each test.
If one motor causes a trip when paired with two others, have it repaired.
If any three motors will run together without a trip, then splitting the circuits will avoid future trips.

Ohm's law
Not just a good idea;
It's the LAW!

 

[dmac123]

Thanks waross for your response and your suggestions.
Splitting the loads is a practical option. We'd need to rewire the junction box to accommodate the additional equipment but that shouldn't be a problem.
Least we will maintain the 30mA protection.
I will also evaluate the drives as you indicated to check for faults.

Regards,
David

 

[waross]

Thanks for the feedback, dmac123.
Yours
Bill

--------------------
Ohm's law
Not just a good idea;
It's the LAW!