0
\$\begingroup\$

I have a query regarding replacing a NTC on a Meanwell dual output power supply. I managed to blow a stepper motor driver and the power supply last night (accidentally swapped a plug to a different stepper driver which turns out was wired differently), and my initial investigation on the power supply shows the NTC isn't allowing mains voltage through.

Unfortunately I have a several day wait for an exact replacement to be sent, and the local electronics store only have generic products labeled 'Epoxy Dip NTC Thermistor'.

I have two questions:

  1. assuming this is for inrush current limiting, will the different style (epoxy vs metal disk) impact the behaviour?
  2. If the different style will work, would there be an impact if a 5 ohm metal disk version is replaced with a 15 ohm epoxy dip?

I suspect if this goes badly it'll blow the NTC or other components on the board before the fuse melts, but I feel it would be a good idea to check with the hive mind to get an opinion from someone smarter than me.

I should add, the characteristics between the original (marked 5D-11) are very similar to the new/expoxy one - the biggest difference is the resistance.

\$\endgroup\$
1
\$\begingroup\$

If the NTC is near the input terminals/connector than it is almost certain that its function is limiting the in-rush current at power-up.

IEC 60950 and UL 60950 clearly states that almost all PSUs must limit the in-rush current at power-up.

If an NTC blows a few seconds after power-up than the problem might be more serious I think.


To answer your questions:

  1. No, I don't think the PSU will "feel" the difference.

  2. The start-up will be slower and the 15 Ohm NTC might get hot under full-load conditions.

\$\endgroup\$
1
  • \$\begingroup\$ Thanks, greatly appreciated! \$\endgroup\$ Apr 15 at 11:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.