I have a dirty transformer - need some advice please.

Thread Starter

boydage

Joined Oct 7, 2016
69
I have been upgrading a control box for a CNC router I have built. I am a tight arse. That means I have done it on the cheap. There are several contactors in my box, a switching power supply, VFD, cnc breakout board. Lots of stuff.

One item I have used is a LC1D32 three phase contactor with a 110v coil, I had one in a box. We are 230v here in the south so I needed to install a small 230/110vac transformer so I could use it.

Ok so my problem is, and it took a while to work it out, is that this 220/110v transformer shares the neutral with everything else. Included is the earth and its earthed very very well. But this transformer is interfering with my cnc control. So bad the cnc machine loses its position. Its a complex box, but I have drawn a very simple circuit of how I have wired this transformer to the contactor. The 230v side is also used for several other items.

Question: Is there something easy I can do to clean up this transformer? Or should I bin it and buy a decent little control transformer, or a 230v contactor?
 

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Thread Starter

boydage

Joined Oct 7, 2016
69
Umm - is it a dumb question but the LC1 contactor is $300 here in NZ. Is it possible to replace the 110v control coil with a 230v one do you know?
 

MaxHeadRoom

Joined Jul 18, 2013
20,927
Why not look at a replacement contactor coil of the right voltage, most manuf make a wide selection of voltage versions from AC to DC.
In a electronic environment you always need a R/C snubber across the coil!
Max.
 

Thread Starter

boydage

Joined Oct 7, 2016
69
Hey Max. Yep I thought of that. And you pushed me over the edge, I bought one. I did know they are available I just like to use what I have.

Guess what they cost in NZ? I didnt get much change out of a hundred bucks. For a piece of plastic with some copper wound on it.

And they wonder why the Chinese copy this stuff and sell it.
 

Thread Starter

boydage

Joined Oct 7, 2016
69
Oh its a Schneider LC1D32. Tell me about this snubber? I have seen a cap sometimes across the input but none of my other equipment has one. Is it to stop it from.....?
 

schmitt trigger

Joined Jul 12, 2010
284
I second Max's suggestion about the snubber. It will assist in decreasing contact arcing.

One caution though: Use both the type of capacitor and resistor which are designed for snubber use. Although actual snubber operation only lasts a tens of milliseconds, the voltage and current stresses are *very significant*.

I have seen improper capacitors explode so violently where the only thing remaining are a pair of leads sticking out.
 

MaxHeadRoom

Joined Jul 18, 2013
20,927
I second Max's suggestion about the snubber. It will assist in decreasing contact arcing.

One caution though: Use both the type of capacitor and resistor which are designed for snubber use. Although actual snubber operation only lasts a tens of milliseconds, the voltage and current stresses are *very significant*.

I have seen improper capacitors explode so violently where the only thing remaining are a pair of leads sticking out.
Actually the one I suggested and shown is across the coil, I have had a few bad experiences with PC based systems where a coil snubber cured intermittent anomalies.
Co's like Telemecanique and Shneider supply add on accessorys such as custom coil snubbers.
Max.
 
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