Transformers TRANSFORMER TYPESInstrumentPotentialTransformerThe instrument potential transformer (PT) steps down voltage of a circuit to a low value that canbe effectively and safely used for operation of instruments such as ammeters, voltmeters, wattmeters, and relays used for various protective purposes.InstrumentCurrentTransformerThe instrument current transformer (CT) steps down the current of a circuit to a lower value andis used in the same types of equipment as a potential transformer. This is done by constructingthe secondary coil consisting of many turns of wire, around the primary coil, which contains onlya few turns of wire. In this manner, measurements of high values of current can be obtained.A current transformer should always be short-circuited when not connected to an external load.Because the magnetic circuit of a current transformer is designed for low magnetizing currentwhen under load, this large increase in magnetizing current will build up a large flux in themagnetic circuit and cause the transformer to act as a step-up transformer, inducing anexcessively high voltage in the secondary when under no load.Rev. 0 Page 19 ES-13
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
