GFP breakers

[mgardner]

I'm working on an industrial project. The owner's production equipment manufacturer (located in Europe) sent us the following request:

"General remark concerning the protection of the power supply:

Due to the servo motors installed in the machine, during startup of the machine or while the servo drives are in motion, leakage currents will appear. This is technically caused and no error. Because of these leakage currents the power supply protection must be as follows:

We recommend the installation of a RCD (RCD = Residual Current protective Device). This must be a selective FI switch. This is a slow type for the use of devices with power filters. It has to be a Type B RCD (sensitive to all currents), with a medium sensitivity (MS) or low sensitivity (LS), typically for protection of machine. More information: http://en.wikipedia.org/wiki/Residual-current_device "

Best I can tell, they are asking for the disconnect feeding their equipment to be provided with Ground Fault Protection. But what I don't know is if I have to specify something special to meet all of their requirements? The circuit is 480V, 20A, 3Ph. Load is 5kW.

 

[mpoulton]

I'm working on an industrial project. The owner's production equipment manufacturer (located in Europe) sent us the following request:

"General remark concerning the protection of the power supply:

Due to the servo motors installed in the machine, during startup of the machine or while the servo drives are in motion, leakage currents will appear. This is technically caused and no error. Because of these leakage currents the power supply protection must be as follows:

We recommend the installation of a RCD (RCD = Residual Current protective Device). This must be a selective FI switch. This is a slow type for the use of devices with power filters. It has to be a Type B RCD (sensitive to all currents), with a medium sensitivity (MS) or low sensitivity (LS), typically for protection of machine. More information: http://en.wikipedia.org/wiki/Residual-current_device "

Best I can tell, they are asking for the disconnect feeding their equipment to be provided with Ground Fault Protection. But what I don't know is if I have to specify something special to meet all of their requirements? The circuit is 480V, 20A, 3Ph. Load is 5kW.

They are asking for a European-style GFP breaker, which they call an RCD over there. A Type B MS or LS RCD. I'm not sure there's an American equivalent for that kind of breaker. It's a GFP device with a trip point of 100-1000mA (MS) or 3-30A (LS), and rated to trip on all fault current waveforms including AC up to 1kHz, DC, and everything in between. As far as I know we do not use anything quite like that over here. I also do not believe their equipment can be considered safe or code compliant on a US electrical system, since it intentionally imposes load current on the equipment grounding conductor. It is unclear why the manufacturer believes this is an acceptable condition. Servo motors are not inherently leaky devices and there is no reason ground fault currents could not be eliminated with proper design.

 

[Jraef]

I'm working on an industrial project. The owner's production equipment manufacturer (located in Europe) sent us the following request:

"General remark concerning the protection of the power supply:

Due to the servo motors installed in the machine, during startup of the machine or while the servo drives are in motion, leakage currents will appear. This is technically caused and no error. Because of these leakage currents the power supply protection must be as follows:

We recommend the installation of a RCD (RCD = Residual Current protective Device). This must be a selective FI switch. This is a slow type for the use of devices with power filters. It has to be a Type B RCD (sensitive to all currents), with a medium sensitivity (MS) or low sensitivity (LS), typically for protection of machine. More information: http://en.wikipedia.org/wiki/Residual-current_device "

Best I can tell, they are asking for the disconnect feeding their equipment to be provided with Ground Fault Protection. But what I don't know is if I have to specify something special to meet all of their requirements? The circuit is 480V, 20A, 3Ph. Load is 5kW.

Is this being installed here? If so, why would you need GFP for something that is only 5kW? It's not going to be a requirement here at 480V. You should make sure of WHY they are asking for a GFP breaker, because if it's due to some EU / IEC regulation, that might not apply here at all.