One way is to hook the primaries up to a small transformer's secondary. First check the primary windings with an ohm meter to tell which leads go to each primary. The small one can have a secondary rating of 12V, say. Then guess, and connect the primaries together. When you hook them to the small transformer, the one under test should not draw much current or load the 12V one. Otherwise, reverse one of the primaries.
You can also use a short lamp instead of the 12V transformer. If you get the connections wrong, the light will glow at full brightness. You can use a 60 or 100 watt light bulb to do the test.
You can also use a short lamp instead of the 12V transformer. If you get the connections wrong, the light will glow at full brightness. You can use a 60 or 100 watt light bulb to do the test.
AudioFreak,
I think you can put the secondaries (identicals) in paralel, applying a 60Hz signal from an generator and, with an scope, see the phase of the signal at the primaries. When tey are the same you can use it has a relative "beginnings" and "ends" for both sides of the transformers. Make it at opposite way works too, but, It's hard to setup and you must use more voltage.
regards
I think you can put the secondaries (identicals) in paralel, applying a 60Hz signal from an generator and, with an scope, see the phase of the signal at the primaries. When tey are the same you can use it has a relative "beginnings" and "ends" for both sides of the transformers. Make it at opposite way works too, but, It's hard to setup and you must use more voltage.
regards
Yes, a transformer has a polarity. We generally don't run into problems with this with single winding primarys or secondarys. once you move to dual windings or three phase its a different story. Transformers induce voltage from primary to secondary through a magnetic field and that field has an electrical orientation. In a dual primary it is possible to wire these two fields to oppose one another much the same as shoving two magnets together - to -. The magnets will force themselves apart, the windings in the transformer cannot. Large amounts of current will flow when this happens. If you don't have a fuse in the primary I would assume that the end result would not be pretty. I realize that I may have not represented the correct terminology in my description here, I tried to put this in laymans terms so everybody could understand this phenomenon. So, go easy on me guys.
Transformer phasing
Actually, the book "Alternating Current Fundamentals" from Delmar Press refers to the leads as poles and goes on to discuss the differrence between additive polarity and subtractive polarity transformers. It lists three requirements for paralleling transformers which are:
1) secondary terminal voltages must match
2) polarities must be the same
3)must have the same percent impedance
The section goes on to describe test procedures for determining which type you have if the leads are unknown.
Actually, the book "Alternating Current Fundamentals" from Delmar Press refers to the leads as poles and goes on to discuss the differrence between additive polarity and subtractive polarity transformers. It lists three requirements for paralleling transformers which are:
1) secondary terminal voltages must match
2) polarities must be the same
3)must have the same percent impedance
The section goes on to describe test procedures for determining which type you have if the leads are unknown.
What the Book Says
Only at DIY can I learn something and help other people at the same time. I love it. Actually subwo 1 has the right idea although this is a secondary test it will tell you if you have the polarity crossed. First determine your matching pairs from primary to secondary by powering up the primarys one set at a time. Once you know which secondarys match which primarys guess at the polarities of the primarys and hook them up in parallel. I would at this time do two things 1) make sure I have a FUSE installed on the primarys (probably around 2 amps) and 2) power up with the secondarys open and make sure the fuse doesn't blow. This will probably tell you what you want to know as far as the primarys are concerned ,but the rest of the test will ensure exact parallel operation. Tie one wire from one secondary to one wire from the other secondary together. You should now have both primarys hooked up in parallel, one wire from each secondary dangling, and one wire from each secondary hooked up. Now using a volt meter, turn on the voltage to the primary and measure the voltage between the two dangling secondary wires. If the voltage is twice the secondary rating you have the polarities crossed. If the voltage is 0 you have the polarities correct. Bear in mind that I crossed my primarys up on a toroid and drew more than 10 amps of current so please use a fuse on your primarys. I have deduced from my misfortune that the opposing magnetic fields bucked each other and caused large amounts of current to flow so be careful. Once you have the polarity correct then you will know the proper phase direction for series operation. I hope this helps.FUSE FUSE
Only at DIY can I learn something and help other people at the same time. I love it. Actually subwo 1 has the right idea although this is a secondary test it will tell you if you have the polarity crossed. First determine your matching pairs from primary to secondary by powering up the primarys one set at a time. Once you know which secondarys match which primarys guess at the polarities of the primarys and hook them up in parallel. I would at this time do two things 1) make sure I have a FUSE installed on the primarys (probably around 2 amps) and 2) power up with the secondarys open and make sure the fuse doesn't blow. This will probably tell you what you want to know as far as the primarys are concerned ,but the rest of the test will ensure exact parallel operation. Tie one wire from one secondary to one wire from the other secondary together. You should now have both primarys hooked up in parallel, one wire from each secondary dangling, and one wire from each secondary hooked up. Now using a volt meter, turn on the voltage to the primary and measure the voltage between the two dangling secondary wires. If the voltage is twice the secondary rating you have the polarities crossed. If the voltage is 0 you have the polarities correct. Bear in mind that I crossed my primarys up on a toroid and drew more than 10 amps of current so please use a fuse on your primarys. I have deduced from my misfortune that the opposing magnetic fields bucked each other and caused large amounts of current to flow so be careful. Once you have the polarity correct then you will know the proper phase direction for series operation. I hope this helps.FUSE FUSE
My mistake. There are two x-former threads going here and I'm stuck with info from both of them in my head at the same time. You have a multi tapped secondary not a parallel one, sorry. I have edited the post you quoted from though it won't do you any good. The book doesn't give a rundown on all types of transformers just single winding ones. If you fuse your primarys and connect them in parallel it should tell you what you want to know. If the fuse blows you have the polarity crossed. If your correct, the fuse holds and you know what the proper phase direction is for each winding. This happened to me with a toroid. What I deduced from my misfortune was that having the polarity crossed I caused two opposing magnetic fields to buck each other which drew a lot of current (enough to blow a 5 amp fuse). If you connect them in parallel and blow a fuse you've got them backwards. I hope this helps as it's all I have right now. I will keep looking
I've not had much time for it but i spent yesterday afternoon playing with it and i've almost got it figured out.... i blew 3 fuses .... when the primaries were out of phase, the secondaries werent twice the voltage.... the fuse blew when the secondaries were out of phase i got 0V when in parallel or series but i got it working so now i've got to check for an approx VA rating.... I'll post all my findings later.
when the secondaries were out of phase i got 0V when in parallel or series but i got it working so now i've got to check for an approx VA rating.... I'll post all my findings later.- Status
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