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What is a Current Transformer?

A current transformer (CT) is a type of transformer used to measure alternating current. It produces an alternating current (AC) in the secondary, which is directly proportional to the AC in the primary. A current transformer, together with a voltage or potential transformer, is a transformer. Current transformers are designed to provide a reduced copy of the current in the high voltage line and to isolate measuring instruments, meters, relays, etc. from the high voltage power supply circuit. Unable to sense or pass through the large AC current of ordinary ammeters, and the current coil of a wattmeter, the wattmeter can be easily measured by using current transformers and ordinary low-range instruments.

How do Current Transformer Work?

A current transformer (CT) basically has a primary coil with one or more turns of weight cross-sectional area. In some cases, a rod carrying a high current can act as a primary. It is connected in series with a line carrying a high current. The secondary part of the CT consists of a large number of thin wires with a small cross-sectional area. This is usually rated as 5A. This is connected to the coil of the normal range ammeter. According to their application in the field, current transformers can be roughly divided into indoor current transformers and outdoor current transformers. According to the insulation method, current transformers can be divided into tape insulation and pouring resin (epoxy, polyurethane or polyethylene).

Index of Current Transformer

A current transformer is a step-down current level step-up transformer in terms of voltage. If the ratio of turns between primary and secondary is 100:05; It will then increase the voltage level by a ratio of 20:01 or decrease the electrical level by a ratio of 01:20. According to IEC Standard 61869-2, Clause 5.201, the rated primary current of current transformers is 10-12 A,5-15-20-25-30-40-50-60-75 A and its decimal multiples or fractions. Its ratio is the relationship between the primary current and the secondary current value; The usual secondary values are 1 A and 5 A. Most current transformers have a power gauge of 2 or 0.5/2.5, are measured at 5/10 VA, and are rated at 35º C and 55º C. A common value for RF is 1.5.