rc filter and insulation monitor

[singapore11singapore]

Hi,
I have an RC filter across the three phase......R in parallel with C x 3 times on one side...all three connected to ground the other..
Connected to the same three phase I have an insulation meter.
I can confirm that when the three phase filter is isolated from the circuit, that the insulation meter is fine.
When the 3 phase filter unit is in circuit, it measures a low insulation.
Can this be due to the incorrect insulation meter being used? maybe the time for the caps to charge is too long and effecting the calculations in the insulation meter thus giving a false positive?
Any suggestions/ideas welcome!
S11S

 

[waross]

Thanks for the drawing. Forget my suggestions and go with Gunnars suggestion.

Bill
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"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

Thanks for showing the transformer nameplate!

I have been thinking about that HUGE 45 MVA transformer (quote: "So the transformer feed is 45MVA....in the heart of the vessel").

It is 4.5 MVA - and that makes it more plausible. Still a big one, but not HUGE any more.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MatthewDB]

It is standard procedure to lift grounds on any EMC filters when you have IT grounded systems. Leave the resistors and capacitors connected as a Y connected filter - they will still filter phase to phase. They will no longer filter line to ground.

Most VFD's have a removable screw or bolt, or a switch to open that will disconnect the EMC filter ground connection. Often there is more than one stage of filtering so there will be multiple screws, bolts or switches.

Trapped charge won't be a problem since the resistors are still there to discharge the capacitors when the drive is de-energized.

 

[singapore11singapore]

Hi,
I.m not sure of the effect of having this ground point now floating will have. I will have a look (google it)! What if anything are the negative effects.
Regards
S11S

 

[singapore11singapore]

Hi,
Have removed the earth from the RC and now find another....on all the drives on the cranes.
See attachment, I remove the armature feedback cable as shown byred arrow and no more earth faults.
With all other cables removed apart from the armature feedback, the earth fault is still present, therefore i believe it is in the Rockwell module somewhere.