Voltage transformer (Potential transformer abbreviated PT, Voltage transformer is also referred to as VT) and transformer is similar, is used to transform the line voltage instrument.
The purpose of the voltage transformer is to transform the voltage, mainly used to supply power to the measuring instruments and relay protection devices, used to measure the line voltage, power and electrical energy, or used to protect the line faults in the line of valuable equipment, motors and transformers
Current transformer, referred to as CT, based on the principle of electromagnetic induction will be converted from the primary side of the current into the secondary side of the current to measure the small current. The instrument. Current transformer is composed of a closed core and winding. Its primary side of the winding turns are few, strung in the line of the current to be measured. Current transformer plays the role of current conversion and electrical isolation.
Extended information
The voltage transformer itself has a very small impedance, once the secondary side of the short-circuit occurs, the current will grow dramatically and burn the coil. For this reason, the original side of the voltage transformer is connected to the fuse, the vice side of the reliable grounding, so as to avoid the original, vice side of the insulation damage, the vice side of the high potential to ground and cause personal and equipment accidents.
Measurement of voltage transformers are generally made into a single-phase dual-coil structure, the primary voltage for the measured voltage (such as line voltage of the power system), can be used in a single-phase, but also can be used with the two connected to the V-V shape for three-phase use. Laboratory voltage transformer is often the primary side of the multi-tap, in order to adapt to the needs of measuring different voltages.
For protective grounding voltage transformer also has a third coil, said three-coil voltage transformer. The third coil of the three-phase is connected to an open triangle, and the two leads of the open triangle are connected to the voltage coil of the grounding protection relay.
Current transformer principle based on the principle of electromagnetic induction. Current transformer is composed of a closed core and winding.
Its primary winding turns are very small, strung in the line of the current to be measured, so it is often all the current flowing through the line, the secondary winding turns are more, connected in series in the measuring instrument and the protection circuit, the current transformer in the work, its secondary circuit is always closed, so the measuring instrument and the protection circuit in series coil impedance is very small, the current transformer's operating condition is close to a short circuit.
Baidu Encyclopedia - Voltage Transformer
Baidu Encyclopedia - Current Transformer