Panel relay/transformer issue

If a relay or contactor is getting a high enough voltage to pull it in then that same voltage is more than sufficient to hold it. Retest the output of the Tx using an analogue tester and only test secondary voltages across both sides of the secondary ie don't test wrt earth or neutral.

Faulty transformers don't usually give out wrong voltages. If any part of a winding goes open-circuit you get nothing, and if it shorts the transformer burns out or blows its primary fuse. I reckon it's more likely that there is a wiring fault putting something in series with the coils that are showing suspect volts. I notice that 60 is half of 120 - have the two coils ended up in series with each other? As per Marvo test across the TX secondary terminals directly. If incorrect, check that the correct primary tap has been used for the supply.

Although it shouldn’t be, is the control supply centre tapped? Was just about to agree with Lucian but thinking about it if the return is lost then both relays will have an equal supply.

Sorry, there’s too many variables to give an answer. Get testing kid!

Your coil supply could be high impedance, your testers sampling rate could stop you seeing the voltage rise and fall and giving you an average voltage relating to peak and duration... -

Drop the wires off the coil and measure again it could be a faulty coil dragging the power down.
Check for short circuits of the TX within the controls most likely on any control wires to a N/O output of the chattering relay.
Do you have a wiring plan and can you post it .
What is your experience with control systems? and what is your electrical background.
Is this a new set-up you have just powered up or an existing one that's been working fine until this happened.

As mentioned already Id be surprised if faulty TX, if your connecting all this up and you have yet to get it running then highly likely you have a wiring error, if existing that has gone faulty then you need to understand how the TX secondary side is set-up to be able to test as coil feedback will make you think voltages are present and ok in parts of the circuit when they are only feedback... is your TX grounded on the secondary in any way to give you a reference?

darkwood said:

Do you have a wiring plan

Click to expand...

AAahhhh we all have dreams....


Its great feeling when you open up the panel and find the drawings inside...




But more often its ....






ha ha

True... was faulting a machine the other day and opened panel an NO WIRING PLANS!!!.. so the longer method to resolve the issue. Customer hovering over me said he hasn't any plans either then said all the cables are numbered won't that tell you what they are?..I said its like finding a street in a strange town without sat-nav or a map and all the street names have been replaced with numbers... all you can really benefit from it is you can easily figure if you find the other end of the street as it still has the same number on it... he went Oh! :charming:

...Similar scenario for me last week working on a settling plant control board,no drawings,but operator had drawings for a similar,older plant..."any use?" he says,Yep i replied,in the same way a 1970's A to Z would help you get about today...a pointer,but you still end up askin' a stranger for help...

The plant operator can be your best friend or your worse enemy. He knows how the plant works and so can help with the sequence. The problems start when he wants to sit on his arse, then you’re up the creak without a paddle.

Older plants drawing are a luxury, if you can find them you will have to piece them together first. Then comes translating the scrawled modifications done over the years.

I would lie awake at night dreaming of a scrawled scribble of any modifications...Luxury...sometimes the best they can offer is a mobile phone number of a lad who used to work with the electrician who left...but now has a mobile pig spit roast business...(actually true!) :cry_smile: