Cold circular saw VFD Conversion problem.

[koslaz]

Hi guys!
This is my Cold circular saw with a Variable Frequency Driver i just attached.
The motor is a 3 phase 1 1/2 hp induction motor 1400 U/s and before the conversion I had only two speeds to choose from, 34 and 68 U/s at the blade.
The 68 U/s was a bit slow to my taste and with the addition of the Inverter I am able to chose between 68 to 136 U/s by increasing the main frequency.
So far so good.
I was making some happy test cuts when suddenly I was hit by the current!
Luckily not with the 380 volts (EU), just 20 volt as I measure it with the multimeter.
The leak is coming from the RFI filter the inverter has (foto).
Is this normal?
I don't know how the RFI filter works. I don't know what to assume.
Do I have a ground problem?
Any help would be really appreciated!

[mactec54]

Hi Koslaz
No this is not normal take the RF filter out of your system & just use shielded
cable & GROUND the INPUT end of the SHEILD ONLY, GROUND one end of the SHIELD!!
The shieled cable will take care of your RF You want to have this on the input
to the drive & the output to the motor & good GROUND'S are Needed

[koslaz]

Hi Mactec54,
thanks for replying!
By saying its not normal,
you mean the filter is defected?

[Al_The_Man]

That looks like a standard RC filter, prevents Inverter noise getting back into the line.
This type is usually used on the input side rather than the motor side.
But I suspect you have not got the ground wire on the unit connected to a good system ground, if you do not, there is conduction via the capacitors to ground wire, and if this is not grounded, then you will feel the effect of the leakage.
Al.

[koslaz]

Hi Al,
thanks for taking the time, I was hoping for your attention!
You mean that is it normal for some leakage from the filter?
I did some Google search and I found this http://www.epanorama.net/documents/p...ounded_pc.html
If I understand correct it seams normal for the filters to have
some leakage current, I just have to make sure for grounding it.
Am I right?

P.S. Excuse my ignorance, I'm just hobbyist in electronics.

[Al_The_Man]

Whenever capacitors are connected from the incoming supply to ground, some small current will flow, as your quoted article points out, so it is important to ensure the ground wire is connected to a suitable valid system ground.
Then you should not feel any effect, if you do, then you do not have the filter suitably grounded.
Al.