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KEMPPI 1500 Mastertig type of varistor RZ 103

AlexNik

New Member
Hi, all members This forum.
Please, help me identify the type of varistor RZ 103 on the filter power pcb of KEMPPI MASTERTIG 1500.
Varistor.jpg
Varistor RZ103.jpg
 

Nigel Goodwin

Super Moderator
Most Helpful Member
It's just a surge limiter, you would need information from the unit manufacturer to identify the one they used, but it's usually not at all critical.

However, it only seems to be feeding a zero-crossing detector, so there shouldn't be any surge anyway?. What values are the two resistors feeding the opto-coupler?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
It's just a surge limiter,
No; look again:

It's in series with the rectifier feed to an optoisolator, not a power system.

It appears to be a VDR that could be used as a voltage dropper for that, ensuring a long turn-off around zero crossings? Or possibly some kind of an "early power fail" brownout detector circuit.

If the welder is for 230V, I think the VDR should have a breakdown voltage (not AC working voltage) of around 80 - 120V.
That will split the power dissipation between that and the 22K, RZ105.
 
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AlexNik

New Member
Thank you for advice. I think I understood how it works. This welder is for 230V, but I dont know what voltage I should take to account, Urms =230V or Upk=230*1.41=324V.
Typical value of input forward voltage for couple CNY65 is 1,25V.
 

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