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What does the polarity mark indicate and what is the importance of knowing the polarity of transformer windings?
Polarity means the direction of the induced voltages in the primary and the secondary winding of the transformer. If the two transformers are connected in parallel, then the polarity should be known for the proper connection of the transformer.
What is the purpose of polarity test of a transformer?
We do polarity test on parallel transformers to ensure that we connect the same polarity windings and not the opposite ones. If we accidentally connect the opposite polarities of the windings, it will result in a short-circuit and eventually damage the machine.
What is meant by transformer polarity?
Transformer Polarity refers to the relative direction of the induced voltages between the high voltage terminals and the low voltage terminals. Instrument Transformers (PT’s and CT’s) and large substation transformers are Subtractive Polarity, so the H1 and X1 Bushings will be on the same side of the transformer.
How is the polarity of a voltage determined?
All voltages and currents have polarity as well as magnitude. In a series circuit, there is only one current, and its polarity is from the negative battery terminal through the rest of the circuit to the positive battery terminal. Voltage drops across loads also have polarities.
What happens if a circuit is not polarity tested?
For example, if you isolate or switch the neutral of a circuit via a single-pole circuit breaker or switch, it would appear that the circuit is dead where in fact it is still live. If polarity is not correctly determined there may be a risk of electric shock during maintenance procedures.
When is the polarity of a transformer additive or subtractive?
If the indicated voltage is more than the applied voltage, the polarity is additive; if it’s less than the applied voltage, the polarity is subtractive. Care should be taken to avoid connecting the 120 volt source across the secondary terminals, as high voltage will be present at the primary terminals.
How can you check the polarity of a transformer?
Verifying the polarity of a transformer can be accomplished with a simple voltage test using the following steps: Make a temporary connection between the primary and secondary terminals of the left side of the transformer (when facing the front of the transformer).