This winding receives electrical power from the source and creates the alternating magnetic field that induces voltage in the secondary winding. In power transformers, it can be either the high-voltage or low-voltage side depending on whether the unit steps down or steps up the supply. In current transformers, it is often just the thick main busbar passing straight through the magnetic core.
Isolate and ground the primary before you even think about opening the secondary terminals on that CT.
Also heard as
- primary winding
Related terms
Transformer
A static electromagnetic device that transfers electrical energy between circuits at changed voltage levels.
CT
Current transformer: an instrument transformer that scales large primary currents down to a standard secondary.
VT
Voltage transformer: an instrument transformer that steps high voltage down to a standard level for relays and meters.
Autotransformer
A transformer that uses a single continuous winding for both primary and secondary circuits.