Here in Australia the mains power is around 240 volts at 50 c/s.
I picked up some secondhand PS transformers that were salvaged from equipment made in the US of A and designed for 60c/s. They have multi-tapped primaries (115v,120v and 125vs) and secondaries of 36 volts @ 3 amps. Now they seem ideal for my purposes and I hope to run the primaries in series and use the secondaries to power some "double mono" power amps. But there is a question about the current that is now available in their adopted country. I have been getting two opposing pieces of advice.
The first opinion says that as they were designed for 60c/s I will need to DERATE the secondary current 20% if they are run on Aussie mains of 50c/s.
The second opinion states the opposite and suggests I now have access to 20% MORE current.
Both sets of advice are coming from well qualified people. Anyone come up with a definitive answer please?
Thanks, Jonathan
I picked up some secondhand PS transformers that were salvaged from equipment made in the US of A and designed for 60c/s. They have multi-tapped primaries (115v,120v and 125vs) and secondaries of 36 volts @ 3 amps. Now they seem ideal for my purposes and I hope to run the primaries in series and use the secondaries to power some "double mono" power amps. But there is a question about the current that is now available in their adopted country. I have been getting two opposing pieces of advice.
The first opinion says that as they were designed for 60c/s I will need to DERATE the secondary current 20% if they are run on Aussie mains of 50c/s.
The second opinion states the opposite and suggests I now have access to 20% MORE current.
Both sets of advice are coming from well qualified people. Anyone come up with a definitive answer please?
Thanks, Jonathan
you will certainly not get more current (VA) by going down from 60Hz to 50Hz.
If the transformer is designed to only run on 60Hz then you will have to de-rate it for 50Hz use. But you are never likely to run the transformer at near maximum rating after start up.
One clue to whether it's suitable for 50Hz use is to check running temperature when the output is open circuit.
If it seems to get too hot then maybe it really is a 60Hz transformer.
I think that adding primary windings will help reduce that heat, but I suspect you will not need it.
Can you safely measure the no load primary current? I guess it should be <=10mA. If it's a lot less then 50Hz is OK.
If the transformer is designed to only run on 60Hz then you will have to de-rate it for 50Hz use. But you are never likely to run the transformer at near maximum rating after start up.
One clue to whether it's suitable for 50Hz use is to check running temperature when the output is open circuit.
If it seems to get too hot then maybe it really is a 60Hz transformer.
I think that adding primary windings will help reduce that heat, but I suspect you will not need it.
Can you safely measure the no load primary current? I guess it should be <=10mA. If it's a lot less then 50Hz is OK.
The seriesed primaries will be good for 2x125=250V at 60Hz, so 240V input is already giving a bit of leeway.
One other thing to note: if you are running the primaries in series, you should ensure both transformers are loaded equally - either by wiring the secondaries in series too, or in parallel.
One other thing to note: if you are running the primaries in series, you should ensure both transformers are loaded equally - either by wiring the secondaries in series too, or in parallel.
Hi Jonathan
If the transformer is designed for standard 60Hz mains input then you are going to need to reduce the input voltage by a factor of 50/60=0.833 at 50Hz or you will more than likely saturate the core. If you have a 250v tap for 60Hz, then the maximum 50Hz voltage you can apply is 208v. Manufacturers do not normally give much leeway except say a 10% over voltage capability as copper costs money!
The loading on the secondary does not have any bearing on this as the magnetising current for most part remains the same despite loading and therefore the flux density in the core remains the pretty much same from no load to full load
Cheers
Ray
If the transformer is designed for standard 60Hz mains input then you are going to need to reduce the input voltage by a factor of 50/60=0.833 at 50Hz or you will more than likely saturate the core. If you have a 250v tap for 60Hz, then the maximum 50Hz voltage you can apply is 208v. Manufacturers do not normally give much leeway except say a 10% over voltage capability as copper costs money!
The loading on the secondary does not have any bearing on this as the magnetising current for most part remains the same despite loading and therefore the flux density in the core remains the pretty much same from no load to full load
Cheers
Ray
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