Siemens simodrive 611 infeed repair ends up in... more repairs

[EPTech]

Hello everyone,

I have been contributing a little since my recent joining of this wonderful forum but this is my first official post, wow. Here it goes.

I have repaired a simodrive 611 infeed module, which is essentially a 400VAC rectifier with regenerative capabilities. It had blown FET and power (fuse) resistor in the SMPS that powers the internal electronics. That one is working. The power relais is enabled and the DC link is charged. I enable the device making the enable input high. When I put the enable pulse high, I can hear the IGBT modules hissing and the DC link voltage lowers slightly. Is it normal that the device goes regenerative (a little bit) when it is idle? If so I consider it repaired.

Now comes the funny part. I do not have a line filter or line reactor in the supply because I was not expecting it to put back something on the net. Anyway, the heating in the workshop went of and came back on. At first I thought it was random and tried again. I quickly realized I was putting high energetic noise on the net and immediately stopped testing. The heating is still working but as soon as I came inside the house I got a whiff of that "sweet" smell of burnt electronics. Slightly panicked I started checking all the electronics plugged in and opening up the defective ones. Turned out the pressure switch on the water pump and the furnace clock died. Amazingly all the cheap wall supplies survived. The defective supplies all had one thing in common. They are the MKT capacitor-resistor-zener or transorb-rectifier type. It seems these cannot handle high power harmonics. Can anyone confirm this? The capacitor is essentially a high pass filter so any spikes and harmonics just pass through, right?

Anyway, I swapped some burnt out power resistors and blown zener diodes and all is well, except the poor contactless tooth brush charger, which is potted in shut. So, limited damage suffered but it could have been worse. Something semi-damaged may still break down later on but as long as I can repair it, I can live with it. I am off now. Have to go and buy a new tooth brush before the wife finds out. She will probably notice it's a new one but I can still say I have cleaned it right  .

[HAL-42b]

I am amazed VFDs don't come with line reactors as standard.

It should be mandatory IMO but that would triple the cost of every switch mode device out there.