Hi everyone,
If a DC load with very big AC component (around 1Khz frequency) is supplied by a AC-DC power supply, what would happen? Is there any harm for the power supply?
I'm having a problem with my AC-DC supplies, when I apply a load with a mean value of 9A (DC), but the AC component has also about 8A peak to peak value with a frequency of 1Khz, my power supplies stop working (something is blown inside) in about 50% of the samples. There is obviously a problem but I wonder is that the high frequency, high amplitude AC component the cause of power supplies' malfunction.
Thanks in advance.
Cheers.

 

It sounds like you may need a higher current power supply. Also, add low ESR filer caps to the input of the load.
What is the load anyway?
More details will help.

 

It sounds like you may need a higher current power supply. Also, add low ESR filer caps to the input of the load.
What is the load anyway?
More details will help.

Hi dendad,
Thanks for your answer.
The load is a radio transceiver, which uses amplitude modulation. The 1kHz frequency of the AC component (unavoidable) is from the audio frequency transmitted by the transceiver.
Both the amplitude of the AC component and the mean value of the DC component are still well within the current limit of the power supply. I'm just wondering is there any limit of the AC component's amplitude for the load of a typical AC-DC power supply, maybe these supplies are designed to supply constant DC loads with very little AC ripple?

 

What is the power supply rated at?

 

What is the power supply rated at?

24V, 30A output. The load peak current is still much lower than the rated capacity.

 

You could try adding some high current RF chokes to the power lines to the transmitter, and extra bypassing at the transmitter.
Maybe a number of these low ESR types...
https://au.mouser.com/Passive-Compo...1yusuiySGT&Keyword=low+ESR+capacitors&FS=True
Try to keep the ripple out of the power supply. It could also be the RF getting in too.

 

I'll try that. But is there any theory related to the amount of AC ripple allowed? Like, is there any way to determine if 8Ap-p is too much for a 30A rated power supply? Or, it can have something to do with the frequency too, as I can imagine, a 10kHz 4Ap-p ripple is even more harmful than a 1kHz 8Ap-p ripple. Obviously these kind of things are not in the power supply's specification sheet.

 

I'm sure there are others that can help with the theory calcs. I'd just try a number of low ESR electros that have a fairly high ripple current rating. What in the power supply has burnt? You may have to add RF bypassing to keep that out of the power supply.
Is the power supply case well grounded?

 

Yup, your DC supply could become unstable.

What I might suggest is 4-quadrant power supply or what's known as a bipolar power supply. They can source or sink current independent of the polarity of the voltage. They may be better known as a voltage source.

These guys http://www.kepcopower.com/bop don;t have anything comperable. You could also try an electronic load. e.g. http://www.testequipmentdepot.com/bk-precision/electronic-load/8540.htm?ref=gbase

 

Thanks for all the info, I will try to fix it accordingly.