[SOLVED] The POS-Output has no electrical isolation to the chassis ground???

[RHeTTRoNiCS]

Hello Guys....after sending him the power supply, my customer complain the following:
1.) The POS-Output has no electrical isolation to the chassis ground.
2.) The NEG-output have some capacitor(loading) issue to the chassis ground.
Is anyone can please explain me more on these and give example.. Really appreciated.

 

[betwixt]

Your question makes no sense unless we know what the power supply is and what your customer fitted it in to. Any power supply can have it's positive or negative output grounded and may have capacitors between those outputs and ground.

Brian.

 

[RHeTTRoNiCS]

Lamda EMS-150-7 power supply 150V, 7A....thanks

 

[FvM]

According to the product specification, the instrument provides 600V isolation for the output circuit. Either the device is defective or the obervation is erroneous.

 

[RHeTTRoNiCS]

We have done bench test after some repair for this power supply..The output voltage is very stable in a full load for 2hrs. We're very confident that the power supply is then working after we repair. But the customer is unhappy when they test it in their system. Their complain is --> The POS-Output has no electrical isolation to the chassis ground. They way I understand is that the positive output terminal is shorted (or low-ohm) with the chassis ground. So it means when they test, there's no output...Really weird, how is it possible. Anyone can explain, please...thanks.

 

[betwixt]

Chassis ground is not part of the output path. If you are only measuring across the + and - connections it may be perfectly good but either of them could also be linked to ground.

Have you done a resistance or insulation test between chassis and the output connections?

I can't see the manual on my mobile phone but if it has 'sense' inputs, check your customer has not grounded one of them inside their equipment because they typically have low resistance in the PSU to the output connections.

Brian.

 

[FvM]

As previously mentioned, the specification assures 600V isolation between output circuit and chassis ground.

The essential new information is that you repaired the power supply. In this case incorrect repair or an previously existing isolation fault, e.g. defective Y-capacitor might have happened.

My suggestion would be to perform always an isolation test after repair.

I think there's no other option for the customer than returning the device. Or, if you suspect a customer handling fault, make clear that continuity test verified the isolation fault inside the power supply.

 

[chuckey]

I would go further, get the customer to isolate the PSU, THEN do the isolation test. They are not using a 2.5 KV tester are they?
Frank

 

[FlapJack]

what is this output isolation test you are talking about. What equipment is needed and how is it done.

 

[FvM]

These are continuity testers with built-in high voltage DC/DC converter. They are used for safety checks of instruments and have switchable test voltages. A handheld tester like a Fluke 1503 could be used with 250 or 500 V setting.

 

[RHeTTRoNiCS]

Thanks to all....am closing this ticket...this forum is very informative