3 phase rcd tripping

[DaleRobbo]

Hey just a quick one,
The factory I work at have built a new maintenance shed, and each work station has a 3 phase outlet rcd protected. Now, my problem is every time I make up a board which contains contactors it trips the rcd.. Is this due to some sort of balance issue? Can some one clear this up for me?
Thanks,
Dale..

 

[Knobhead]

3 pole RCD or 4 pole? How is the contactor control wired? Too many unknowns.

 

[DaleRobbo]

Sorry mate, I was hoping it was going to be a straight forward answer.. It's a 4 pole rcd protecting my workstation. As for the contactor, it has a 24v coil and was feeding power to 2 vsd's. Theres also a transformer there as well for the control side of things.. The contactor is only for an estop, so once power to the vsd's drop they go into a fault mode and have to be reset by myself from the board..

So it may be the contactor, vsd, or transformer tripping the rcd? Either way it's annoying but I kind of like the idea of having a rcd at my work station, and I guess I just want to know why it's tripping before I bypass the rcd.. Any ideas mate??

 

[Knobhead]

Likely culprit would be the VSD’s

 

[bertt]

Please make something simple for me.

• ON/OFF on one contactor with coil 24V (same power supply 24V DC used for your scheme).
• No phases linked to your contactor.
• Only ON/OFF on contactor coil.

1. I want to know the power of your voltage transformer (230V/24V) and your RCBO protection value (Amps?) if you use same (one of phases) as circuit for command.

Thank you.

bertt.

 

[Darkwood]

Have to agree with Tony here.. VSD's have designed earth leakage hence the strict earthing set up you have to comply to... if your flexible on the brand i can get info on a RCD friendly VSD ive used a few times but the ruddy name eludes me.

 

[Knobhead]

Ditch the RCD if you’re working on VSD’s. Or fit a 100mA unit, which would be a waste of time if you’re wanting shock protection.

 

[DaleRobbo]

Yea thanks for your thoughts guys. Think I'll just ditch the rcd. No stress on finding out the name of that vsd darkwood, we only use Rockwell gear and I can't see that changing.. Thanks again!

 

[bertt]

Hi,

Please do something for me.
Take a picture with your RCD and about the 24V, DC power supply. At least the label from your 230V/24V voltage transformer.
(If you can tell me about the 230V/24V circuit if you use OR not one of phases who are going to contactors as well will be usefull.)
Thank you.

bertt.:20::boat:

 

[Darkwood]

Ill make a few calls see if i can get the name of them ....bare with us.

 

[bertt]

Hi,
I add a picture about 24V coil - contactor.
Thank you.
I look forward hearing from you.

bertt.:juggle:

 

[Darkwood]

Bertt im not wanting to rain on your fire here but what are you wanting to know?..... a transformer in itelf wont trip a rcd unit unless it was faulty... also if it was a DC power supply th rectified waveform would give minimal leakage for a dc supply rated for only E-stop circuit. The contactor again won't be a cause unless again the coil is faulty or somekind of contamination has gotten onto it.... The OP has already explained hes running VSD's and these normally give out high leakage to earth in the way they work... i can bet if OP drops the power off the VSD's or leaves just one connected he may find the nuisance tripping dissapears and all his control circuits work fine.

 

[bertt]

I have to go now. sorry till tomorrow.
If you use 24V DC you got for protection a rectifier diode one on each 24V/DC coil. (1N4007 it is the code).If it is dead the value it is 0 ohms.
That so many questions.
Thank you.

bertt.:wacko::boat:

 

[bertt]

Hi,

It isn't just a light bulb even the solution could be simple.

IN to OUT view:

RCD /RCBO 3 PHASES

1. CONTROL circuit

• P [W] =???/24V(OK) / DC (± Polarity),
• Classic Linear Power Supply OR Switching PS…???.
• Protection control circuit RCD, RCBO, MCB ….???

2. 3 Phases circuit

• 3 or 4 poles contactor command - 3L,N OK.
• Protection electrical motors circuit(s) RCD, RCBO, MCB ….???..A/30mA???

What it is happening as order?
Thank you.

bertt.

 

[Darkwood]

Hi Bertt.. the OP has already said he's omitted the RCD now and we can almost be certain the cause is the 2 VSD's as they give designed earth leakage and are No1 suspect with the information we have been given, im trying to find out the model of VSD that limits this nuisance tripping but alternatives are SI units that ignore the characteristics of the leakage created by VSD's, Computers etc and only trip on true fault leakage ....that is if he still want to have earth leakage protection.