Inverter Leakage Current

So, you have 60 inverters in a single cabinet and the combined leakage current is 3A. 3A spread over 60 inverters averages out to 50mA of leakage current per inverter.

Is a 50mA leakage current per inverter within the limits specified in the inverter data sheet?

If yes, then you have too many inverters off the one incoming feeder - Increase the earth fault relay setting (if this is allowed within your local electrical standards and regulations) or add a second feeder and spread the inverters across the two.

If no, then you may have one or more inverters that are "leaking" more current to earth than they should - check the current thru each individual inverter earths and replace the "leaky" inverters to fix your problem.

Another alternative is to turn on half the inverters at a time, hence reducing the earth leakage current during inverter turn on (if the leakage current is due to capacitors reforming when power is first applied after the inverter has been off for a while).

Thank you very much ,Jack of all trades.

Let me know u have 3 Ph 4 wire OR 3 Ph 3 wire inverters or mixed.

Best solution that can be tried is

option 1 connect all Neutral of all and grond at a point n simultaneously all inverter base and supply socket earth/ground shall be joined together and grounded at a point same as neutral.

option 2 if u have ony 3 ph 3w output of all then separate neutral wire where u measure leakage current. Check all invereter body voltage to earth is below 50 volts. with this u will be able to pinpoint a faukty inverter.

did you the rigth phasing of your. because the leakage ampere it cause by in proper connection. kindly checked all the wiring connection fom mccb to relay.

thanks.

more power;

dear,

following action may be taken....

1. Relay must be earth leakage relay... If it is earth fault relay, it should be of the range of 5 Amp. with CT of 250/5 Amp. with setting at 10% of full rated current of 250 Amp.

2. IF you have a sensing CT for 2 AMp earth relay, it may be replaced by higher ( double the existing CT ratio ) current ratio.

regards

Check also that neutral and earth are not inadvertently connected together somewhere on the installation. It might be somewhere completely separate from where the perceived problem lies.

• For example, a main domestic 100mA incoming earth trip operated when the load on an oven circuit downstream of it exceeded about 25A, even though the oven circuit is in itself protected by a 30mA trip that didn't operate. The fault turned out to be a neutral and an earth conductor touching each other on a separate 6A lighting circuit connected to the main board. It took 2 days to find it!

These things are a pain in the botty to find, though finding them and correcting them may be a lot more attractive than major, unneccessary, surgery to the distribution system.

Some inverters/VFD's have a large value resistor that ties from internal rails to Earth.

this shunt/resistor can be replaced or removed depending on its application.

Possibly the best thing is to go back to the manufacturer, explain to them your problems with their machine, and ask if they can rectify them.

If you tamper with their machine, you could push it out of warranty, and if something major happens, your up for the full repair, if you get them to modify it, then you could be safe during that warranty period.

Check and see if your individual drives have ground fault protection. Many do as standard these days.

With 60 inverters you will have significant AC noise and I would not be surprised if the total was into 10's of amps.

You do not state what country you are in, and that will determine code grounding practices.

Many drive systems will be supplied with drive type shielded Delta Wye isolation with high resistance neutral grounding and ground fault alarm only.

The individual drive ground fault detection should give adequate protection of your system. You may want to consider the implications of defeating your incoming protection.

You may also want to check the incoming phase to ground voltage balance, and the phase load balance.

Many drives reference their feedbacks to ground potential and the sum of 60 drives especially with imbalances may tip you over your threshold.

Dear GW,

Thank you for your reply , I am from Malaysia, we have the transformer Primary delta 22000 v 3phase 3 wire system and secondary star 415v 3 pahse 4 wire system (neutral and earth together at the transformer star point)

Are the secondary phases balanced in voltage and current?