Anyone have any experience calibrating a Elgar single phase power supply?

 

Whenever I have used such an AC power source, I have used calibrated instruments to measure the voltage, current and frequency.

 

Yes, as mentioned use instruments with a minimum 4:1 accuracy ratio meaning the instrument used to measure a parameter should be a minimum of 4 times more accurate than the unit under test. Elgar is an old name in power supplies and you make no mention of model number? Generally on the older units we would test them under a load for rated current and also line input regulation using a Variac (auto transformer). We would also use a scope to measure output ripple component. Again a model number would help?

Ron

 

Again a model number would help?

Thanks Ron,
The model number is 1751SL. The problem is the test board inside the plug in programmer model 9012, that is inside the 1751SL. It is not displaying the current correctly. I have verified the current output using a load and calculating the current.

Brad

 

Been a long time but looking at this Elgar manual around pages 2-6 through 2-10 it looks like they use a CT (Current Transformer) circuit with a few shunts including a 100 ohm pot to measure output current. Now if that doesn't apply I would start looking at how they sense and monitor output current. There should be an adjustment. With the big Elgar units we would use a large Leeds and Northrup standard resistor as a load and measure the voltage drop across it. I remember the frequency plug in modules so make sure whatever meter you are using measures true RMS (not average responding RMS indicating) and is designed to work at whatever frequency you are using. Gone are the days when manufacturers included complete schematics and calibration/maintenance procedures in their manuals. I don't even know if Elgar is still in business? If they still exist you could try a phone call to them and get an applications engineer maybe. I remember the big Elgar units as brutes and you needed a hand truck to move most of them. Anyway I would start at the output metering and work backwards.

Ron

 

During my work I’ve used an Elgar unit with an output rating to 3kVA and another smaller unit at 350VA.

It’s too much trouble to have the units’ displays calibrated – and much easier to use calibrated instruments.

The Elgar units are very stable in terms of their output, typical voltage regulation would be less than 1% (from no load to full load), with the output voltage total harmonic distortion less than 1% (with a typical mains supply in the UK being around 2%).

Elgar were taken over by Chroma who still make AC power sources. Until recently they had Elgar manuals freely available on the website – but it looks like you now need to contact them for their legacy product manuals.