disconnect re-connect grounds

[rwomack]

I must do Hi-Pot and functional test on a product.

The product produces nasty -6KV transients on the neutral side. For Hi-pot testing I must keep the ground and neutral isolated. The product chassis must also be isolated from the system to properly measure ground continuity with the hi-pot tester.

Durring the functional test, I need to bring the neutral and ground both to hard equipment chassis and/or earth ground for safety (operator interaction with the product is required) and to suppress noise on the neutral side. Is there a NC "relay" that is rated as "acceptable" to provide a disconect and reconnect of the safety ground? Looking for relay to make a very solid connection, dependable and safe connection over the long haul. Any ideas?

 

[VEBill]

How about using (carefully selected, carefully placed) connectors to provide these 'disconnects' for testing? Connectors (done right, including both sides of the circuit) wouldn't raise eyebrows; neutral disconnecting relays certainly would.

(And you might want to look into those -6kV spikes on the neutral... ...yikes!)

 

[rwomack]

Thanks VEIBLL,

This is supposed to be an automated test except for the operator cycling the power switch once. I also thought that switching leads/connections might be the best, but would add time. I did not know if there was a special type of relay or contactor for reliably making the safety ground connection, other than a normal contactor.

The unit produce a normal 6KV output. When it gets shorted, switched on and off, etc. There can be nasty transients on the neutral side that wreak havoc on the test system, if you don't have the neutral well grounded just as it leaves the DUT. But can't hipot test in that mode

 

[VEBill]

...The concept is to put a UUT test connector in ~JUST~ the right place so that when the test operator goes to make the test, they are able to make all (!) the necessary disconnections and test connections - all with three movements (unplug UUT's test connector, plug test cable 1, plug test cable 2).

After they're done: unplug test cable 1, unplug test cable 2, re-plug UUT's test connector. Done.

The feasibility of this approach depends on the details of the design.

I can't see adding a relay to a product simply to save perhaps a minute during test. Test techs aren't usually THAT well paid (although they're often worth their weight in gold).

 

[rwomack]

Thanks again,

Sorry for my poor explanation. The relay was just one for the test system, not product.

 

[VEBill]

Okay - I see now - you're planning to do both Hi-Pot and Functional at one station without moving test cables and you need to finangle the ground and neutral wiring. Sorry I didn't understand at first. We've always used separate stations for hi-pot and functional.

For reliability, maybe you would need opto-isolated safety sensors monitoring and interlocking everything to avoid shocking the test techs. Any relay might eventually fail...

Good luck.