This is the best advice I could give. Once you learn this trick, you may be surprised how many times it comes in handy. The secondary is often the outer winding on the core and once you find the outside end of the wire, it's easy to pull one wrap up and out at a time, measuring the voltage to see if you're at 18 yet. If you repeat the same exact process on four matching transformers, you could connect them all in parallel (observing phase) to form an 18 volt, 20 amp transformer bank.
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Tranformers/Power supplys
- Thread starter Tweetybird
- Start date
This is the best advice I could give. Once you learn this trick, you may be surprised how many times it comes in handy. The secondary is often the outer winding on the core and once you find the outside end of the wire, it's easy to pull one wrap up and out at a time, measuring the voltage to see if you're at 18 yet. If you repeat the same exact process on four matching transformers, you could connect them all in parallel (observing phase) to form an 18 volt, 20 amp transformer bank.
This is something we should all consider, especially if the transformer being repurposed was not intended for continuous use. For example, microwave oven transformers will get hot with no load placed on them if the primary is energized for an extended time. This is the result of cheap core material and using the least amount of primary turns on the transformer. This practice doesn't provide enough inductance to the AC line, in order to appear as an open with no load applied and causes heating over time. The bigger the cheap transformer is, the larger these losses can be.How many amps do they draw when not working?
When you say 20 pounds and they can "draw" 5 amps when working, that suggests these transformers are hundreds of watts each and were probably used for under water pool lighting before LED technology. Can you confirm if the 5 amps is actually what is "drawn" from the line and if it's 120 or 240 volts?
Been there with the microwave transformer. It went to the dumpster.
If your line voltage is 120, you can buy cheap microwave oven transformers with 240 primaries operated at 120 volts and get around that heating problem. This usually reduces the HV to a more appropriate value for most applications too.