Dc Power Supplies Elevating N-g Voltage

[chaterpilar]

I have a panel which 10nos. of 24 vdc @10 amps power supply units all having input of 220 vac.

 

I noticed that the neutral to ground voltage ( at the panel ) increases from 0.2 volts AC to 14 volts Ac when the Dc power supplies are put ON.

 

What is the cause of this?

 

Whether EMI filter on input (AC) side help reduce this voltage.

 

Chaterpilar

[marke]

Hello chaterpillar

 

I would suggest that you look at the voltage waveform with an oscilloscope and I expect that you will find that the voltage is in fact a lot of switching noise.

If you use an electronic type meter to measure the voltage, it can be high due to mos electronic meters being responsive to the peak of the waveform. If you use an old analog meter, you may find a much lower reading due to the meter operating on the average levels.

It may be necessary to add some good EMC filtering to the input of the power supplies.

 

Best regards,

[mariomaggi]

Dear chaterpilar,

another possible cause is the presence of harmonics originated by your powers supplies. In this case an RFI filter will give poor results.

 

Regards

Mario

[Carl]

Is the 0v of the power supplies connected to earth. I usually leave this out if the power supply is a switch mode type sometimes you have no choice as the casing of the power supply is the same point as 0v. The subject of should I ground my power supply or should I not is debatable

[chaterpilar]

Carl thanks for your reply.

 

The 0v is not grounded but the powersupplies ( 10 nos) are all mounted on a din rail, and as you said may be ground loops are being generated because the powersupply base is grounded.

 

chaterpilar