Non-Standard Transformer

Hope you know at least the VA rating of the transformer ,then get a dimmer-stat readily available with AE ( Automatic Electric )dealer and set its output at 54 volts and seal it and connect to your load and solve your problem immediately.Their telephone number is 91-80-22242095. Later you can order one from National Controlling Equipments Industries Haryana. Contact details nacei@rediffmail.com They make non standard transformers on specific order. There may be some manufacturers in Bangalore itself who can supply it.

Unsafe, most dimmers do not isolate and the waveform is rarely a sine wave either.

Could kill someone with this proposal or burn the equipment...

Andy Germany ,

The AE make Dimmer stat is an auto transformer.( Probably the terminology used may be confused to be inverter)There is no danger in using auto transformer in place of isolation transformer so long as the system is properly earthed and there is no specific requirement for primary secondary isolation functionally.Probably you might have taken it to be an electronic inverter. There is no frequency change in auto transformer. We always use auto transformer when transformers with odd voltage ratio fail and immediate replacement is not available. In 40 years of my experience I have used it in many occasions and have never come across any accident in using auto transformer to replace isolation transformer when damaged.

I hate to say this, but I feel that you have had great luck in not killing anyone if what you say is true about the way you have used autotransformers during the last 40 years!.

An autotransformer does NOT isolate the input mains from the output. But provided safety precautions are fully taken care of on the secondary side, this danger can be avoided, but as many inexperienced people read CR4, I have to make sure that they are not put under a false impression of safety from your words regarding autotransformer.....sorry!!!

You may know what you are doing and when, but they cannot learn from you safety when you do not cover it fully.....I will attempt to correct that here and now.

Here is a simple drawing of a normal Autotransformer taken from Wikipedia, is this the transformer that you were were referring to?:-

As you can see, the primary input and the secondary outputs are directly connected with each other via the single transformer coil in one case and directly with the other.....inductance but little resistance....

The whole link may be found at:-

http://en.wikipedia.org/wiki/Autotransformer

Autotransformers must ONLY be used where the secondary output is treated and insulated/isolated as though it was the mains connection itself.

If you read through the Wiki article fully it mentions this point:-

Limitations

A failure of the insulation or the windings of an autotransformer can result in full input voltage to be applied to the output. This is an important safety consideration when deciding to use an autotransfomer in a given application.

It does not even mention the fact that the "straight through" connection needs to be connected to the Neutral, not phase, but in countries where there is no definition of neutral or phase (USA & Europe, but not the UK for example) this can happen....Really really dangerous indeed.....

Maybe you are mixing up another transformer type with Auto transformer, which would explain the errors/misunderstandings you have made. Please explain where we have misunderstood your comments if that is true....but a normal (as shown above) Atotransformer is a really dangerous beast for anyone who does not understand its quirks......hopefully you do and only your explanation was not fully correct!

Happy Christmas.

Just because no accidents have happened, does not mean that a potential hazard is not there.....driving on the left hand side of the road in the US and Europe, only causes an accident when someone comes from the opposite direction!!! Possibly!!

Andy Germany : When the full plant stops working and production come to stand still as a maintenance manager you have to ensure that the machine restart immediately. The use of auto transformer as a make shift temporary arrangement become essential when immediate replacement is not available. Theoretically it look is a bit unsafe but with proper protective system and proper safety checks after considering the operational safety in the specific cases .By experience you can asses it and the arrange met works safely with out any accident. It is not simple luck that no accident happened but the proper checks and arrangements and the caution given to staff concerned make it work.If you don't take such minor risks you will be out of job.Such arrangements are not permanent but for a day or two till your original transformer is replaced.

Merry Christmas

I agree with #6 This is a very unsafe recommendation. Injury or electrocution could result.

Block make a range of transformers with lots of link combinations for varying the turns ratio. If you go to the RS site and look up order code 419-7439, you'll find a 250VA one designed for 2 x 0-115V outputs with a range of input voltages from 208 to 600.

If you work the sums, you can get 53V out for 240V in by linking terminals 31-35 and wiring the outputs in parallel. Since (I assume) you're only working with a nominal 240V (and you haven't mentioned regulation), this should be near enough!

Depending on the required current, you might use a Variac (variable transformer), and set the output voltage to 54 volts until you find a suitable replacement for your defective transformer.

Only if it is of a type with an isolated output, otherwise far too dangerous.....

If the electric heating element is safer when powered by a floating supply, then obtain the correct transformer or use the variac or the lamp dimmer through an isolation transformer. Resistance heaters generally don't care whether they are powered by pure sine waves.

...and what if it has a PIC or similar controller inside? Then it might get some real problems as sometimes the mains is used as a slow clock for cheapness.....

we have got it repaired locally. I would like to get and keep one a spare. Also in talks with RS.

Thanks to all for their support and response.

Shivaram