Hi Experts,

We have three lines of single phase pumps (10 users drives per line). These will start/stop at random.

We want to have earth leakage/residual current protection on the drives so we would like to go for a toroid and protection relay option as the main panel breaker has a shunt trip.

The question:

Will a single toroid (bear in mind that amps can differ significantly between phases) and protection relay at 300mA work in our case or do we need 3x single phase earth leakage devices?

Many thanks!

Hello Danie;

I can suggest  these links to help you design your residual current protection application for AC drives:

https://support.industry.siemens.com/cs/ww/en/view/109482301

Siemens Residual current protective devices (RCDs, RCCBs) YouTube · Siemens Aug 25, 2017

These documents should give you most of ghe information you need.

Hope this helps, 

Daniel Chartier