Need Help Diagnosing Automatic Voltage Regulator/Stabilizer

[sblrog]

Hello,

 

I was wondering if someone could help me diagnose a problem with a 220V, 1000 VA automatic voltage stabilizer/regulator. It's a relay-type, containing 5 relays. Usually, when I plug it in with no load, one relay (or more?) starts clicking non-stop, while the output stays steady at zero volts. Sometimes, the clicking stops after a few seconds, with the output still being 0V. Very occasionally, the unit will work properly when I plug it in and load it up with a floor fan, maybe ~40W (I haven't tried anything heavier on these extremely rare occasions).

 

Any ideas for me to try out? I would say that I have maybe an intermediate knowledge and ability when it comes to repairing electronics and electrical appliances.

 

Thanks in advance for any help you can give me,

 

Rog

Edited September 15, 2016 by sblrog

[studiot]

First you need to provide a proper case history.

 

Is this really a 1 megawatt stabiliser?

 

Stabilisers require a minimum load (usually somewhere between 1% and 10 % of full load) and some (not yours luckily) will actually fail destructively if this is not provided.

 

So can you get the stabiliser to operate reliably with such a permanent load?

[sblrog]

First you need to provide a proper case history.

 

Is this really a 1 megawatt stabiliser?

 

Stabilisers require a minimum load (usually somewhere between 1% and 10 % of full load) and some (not yours luckily) will actually fail destructively if this is not provided.

 

So can you get the stabiliser to operate reliably with such a permanent load?

 

Sorry, big mistake there. It's 1000 VA (not kVA; I have corrected the post). This is a household unit that is commonly used in developing countries where electrical utilities may supply power that's a bit unstable. Usually it outputs 0V, so no, it won't operate either with a load or without.

 

The history of the unit? Was used to protect the compressor of our refrigerator (keeps output voltage around 220V when voltage supplied by power utility fluctuates above or below). Worked fine for a few years, but we left the country for a year and when we came back, it was behaving as described in original post.

Edited September 15, 2016 by sblrog

[studiot]

Since it is a relay system, what drives the relays?

 

A stabiliser will have some sort of measuring system on the output and compare this with the reference.

It then switches the relays on or off to increase or decrease the juice.

 

If the relay contacts have become welded together through some overload. Or if pitted through overload and then left for some time corrosion can also fuse the contacts.

 

Otherwise the control system may have packed up.

[sblrog]

Since it is a relay system, what drives the relays?

 

A stabiliser will have some sort of measuring system on the output and compare this with the reference.

It then switches the relays on or off to increase or decrease the juice.

 

If the relay contacts have become welded together through some overload. Or if pitted through overload and then left for some time corrosion can also fuse the contacts.

 

Otherwise the control system may have packed up.

 

I can see a couple of op amps, I'm guessing for voltage comparison purposes. From other research, I'm guessing that the control system sends a control voltage to the appropriate relay coils to open or close the relays.

 

Thanks for the comments on possible relay failure modes. I'll try to figure out if the relays are supposed to be normally open or closed, and then see if there are any faulty relays that I can replace. If it's the control system that's damaged, that's gonna be beyond my ability to repair.

 

Thanks again,

 

Rog