what is the third wire on the secondary windings of a step up transformer for?Please explain fully.?

Question

i don't have a clue what it does..........

Answer 1

measure the resistance of the third wire to each one of the two wires, compare your reading from the resistance of the two wires(measure it too). from this readings, you can conclude whether it is a tap , either center tap, lower voltage tap or higher voltage tap.

Answer 2

Step up, or step down, it really doesn't matter, that third wire splits the secondary into two more or less identical halves. For power transformers, such as to power a stereo amplifier, it can be used to provide the ground for a full wave power supply. Using 2 diodes connected to each of the main wires, and the lead of each diode that is not connected to the transformer lead are connected together, this becomes the positive terminal (usually) for the rectified voltage and that center lead is the ground return. Using a 4 diode full wave bridge across the main leads of the secondary, the center wire becomes the ground for both polarities that are derived from this configuration. This configuration gives a negative polarity voltage supply, referenced to that center lead, as well as a positive polarity voltage supply, referenced to that same center lead. A good reference manual that would explain these concepts can be found in the ARRL Handbook for radio amateurs.

Answer 3

Its a ratio tap ... Do like the other fellow told you to do measure the resistance if its greater you got a higher voltage(more coil to coil ratio) if its lower its lower voltage ...sometimes people like acme give you a percentage tap of 100% this acts like a noise filter to reduce RFI check the res. against the primary it might be like that... Look for a schematic on the thing.... Acme dry transformers are a good source contact them and get a catalog...also these might be set up as a buck boost system where the extra tap is is 50% of primary .hook up the primary get out the DVM and set on autoranging an test it out....be careful though....it might be a shocking expierence..Good luck from the E!!!

Answer 4

Are you sure it isn't a step-down transformer?

Please update your question with the primary and secondary voltage ratings as well as the kVA rating of the transformer.

Answer 5

if it is a 3 phase transformer then it acts as the third phase. But if single phase then it is mainly to earth the transformer.