how to test a transformer for quality

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Fahime

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Hi,
I'm going to make a power supply adaptor. I have several transformers with the same charactristics. I want to choose the best quality one. How can I test them to find which one is the best-made?
 
i feel that the no load primary current (secondary opencircuit)should be minimum. this is possible with best laminations. like CRGO

If the input voltage is likely to increase (as in some countires during non peak hours), the core should not saturate- this can be checked by the heat of the trnasformer at higher voltage inputs(say 265V for a 230V promary transformer)

Next is saturation of core and secodary wire heating up due to non stadard gauge for 110% of designed load current .
if these parameters are meat and the ratio is good to get the correct voltage at the secondary , we may perhaps consider the transformer to be a good one.

as it is not possible to physically check a transformer before we purchase it, we ahve to ask for detailed specifications from the manufacturer or seller.
 
Regulation is also important - the lower the difference between the loaded and unloaded voltage the better.
 
Once the core is proper and copper wire ised for Primary and secondary are of proper gauge and the turns pervolt is maintained honourably, i think, the regulator woud be myuch better. as anyway we will use electronic regulators, balance is taken care of.
 
mvs sarma said:
i feel that the no load primary current (secondary opencircuit)should be minimum. this is possible with best laminations. like CRGO
Click to expand...
Yeah, I once bought a cheap (in both senses of the word) isolation transformer. I think the brand was Triad. It runs so hot under no load that you can't touch it. I thought it had a shorted turn or something. I emailed the company, and one of their engineers replied that it was designed that way. It works OK, but I wish I had bought one with higher primary inductance. It would have probably cost more, because it would have required more copper, but I don't like having another hot thing on my bench.
 
Designer may say it was designed like that-- except in magnetic amplifier based servi regulators which i remember to have studied in 60s,(wherein there used to be a moved shorted winding inside a transformer like thing.) this device was used as voltage stablizer.
you have perfectey commented that one need not have a HOT thing on our tables ..
BTW where is your palce "Hew Hess of Hay"?
 
"Hew Hess of Hay" is a corruption of U. S. of A. (United States of America), and came from the Li'l Abner comic strip.
 
mvs sarma said:
Thanks to Ron (Roff)-- it is news -- for me.
a colloquial way of calling USA.
Click to expand...
I think the Li'l Abner comic strip was a cultural thing, probably unique to the United States. The strip was retired by its creator, Al Capp, 30 years ago, so most people who remember it, and things like "Hew Hess of Hay", are Hew Hess of Hay residents 45 and older. I'm 66.
 
I have heared of Li'L Abner, but I cant remember when I last saw a reference to him, not something which has been popular in the UK.

As regards the Hew Hess of Hay, there is a common tendency among some groups of English speakers to "drop the H" so that Hello becomes 'ello, House becomes 'ouse.
There can also be a tendency amongst other groups (very rare) to put in a leading H where one should not be.

So, US of A (phonetically ew, ess of ay) becomes Hew Hess of Hay.

JimB
 
Cockney? Their "English" sounds weird.
Scottish speech also sounds weird.

The Yew Nighted (Knighted?) States Of America sounds just like this.

Eat your haggis, Jim.
 
JimB said:
There can also be a tendency amongst other groups (very rare) to put in a leading H where one should not be.
Click to expand...
I think I've heard that before, it seems to be more rural areas like remote aparts of Norfolk.
 
I feel bad , having unnecessarily diverted the topic-- anyway, general electronics-chat section ,
hope we have to be back with the transformer, in order to help Fahime the OP
 
Fahime said:
Hi,
I'm going to make a power supply adaptor. I have several transformers with the same charactristics. I want to choose the best quality one. How can I test them to find which one is the best-made?
Click to expand...
I think it depends on your definition of quality. Here are some things you may or may not need to consider:
1) Temperature extremes.
2) Efficiency.
3) High voltage between primary and secondary.
4) Capacitance between primary and secondary.
5) Electromagnetic radiation.

I'm sure there are others, but before you begin testing, you have to decide what is important to you.
 
Regulation is important because transformers with better regulation are also more efficient - the two charicteristics go hand in hand. Also, you might think it isn't important as the electronic regulator will take care of it but it is important. The output voltage is always specified at no load so if the regulation is poor it might be 50% higher off load and if you haven't alowed for this your filter capacitor and possible the regulator will be toast.

Larger transformers are more efficient than smaller transformer. A crappy little 1VA wall wart unit will be less than 50% efficient whilst a huge 1GAV unit will be 99.99% efficient.
 
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