Hi,

I am having a problem where our power supplies sometimes don't work on startup. This condition presents on machine startup after the machines have been turned off 2-3 days. Here is the sequence of events:

1. Machine is turned off.
2. 2-3 days pass.
3. Machine is turned on. Note: we run the power supplies using the remote on/off signal. This signal allows us to turn on the machine and provide AC to the power supply, and then selectively turn on the DC output.
4. Remote ON, power supply does not provide any power. PSU is receiving AC because status light is on.
5. Turn off primary power to machine for at least 30 seconds.
6. Restart.
7. Remote ON, power supply works fine.

PSU model: RSP-750-24. Note, this only occurs after machines have been in service 3+ months, where power is cycled (AC applied) once per day. Remote ON circuits work fine, no major visible corrosion on units.
PSUs are run on CC mode, with voltage left to swing to max 24 V output.

Any ideas? Anyone encounter this issue before?

 

Sounds like the over-volt protection is being triggered. Sometimes a small static load on the output terminals will stabilize the turn-on ramp.
https://www.meanwell.com/Upload/PDF/RSP-750/RSP-750-SPEC.PDF

SPEC note 5.
There is a high possibility of triggering the floating over volt protection ...

 

Sounds like the over-volt protection is being triggered. Sometimes a small static load on the output terminals will stabilize the turn-on ramp.
https://www.meanwell.com/Upload/PDF/RSP-750/RSP-750-SPEC.PDF

SPEC note 5.
There is a high possibility of triggering the floating over volt protection ...

Hi nsaspook, thanks for the reply. We've considered the overvoltage protection being triggered as the likely culprit. But, some conditions don't add up:
-The problem does not present itself if machine is turned off for less than 2 days (if we leave off overnight, the machines run fine the next day). i.e. what process over an extended period of time could be causing this issue?
-Why does the problem resolve on restart?

 

Hi nsaspook, thanks for the reply. We've considered the overvoltage protection being triggered as the likely culprit. But, some conditions don't add up:
-The problem does not present itself if machine is turned off for less than 2 days (if we leave off overnight, the machines run fine the next day). i.e. what process over an extended period of time could be causing this issue?
-Why does the problem resolve on restart?

The only proper way to find out the root cause is to instrument the power supply output and loads with a fast data-logger to isolate the issue. I've no idea what physical, mechanical or electro-chemical process the machine uses the electrical power for. In general, moving parts wear and bind from static contact, moving parts stick with friction from static contact, processing chambers get coated causing shorts on startup over periods of time, the list is endless...