Should a current transformer be connected?
Thread Content
For a 50kw three-phase motor, is it necessary to install a current transformer when connecting it to the control circuit? Why?
It depends on whether you need current display or thermal protection. Of course, for thermal protection, it depends on whether you choose an intelligent device or a thermal relay. Unless you opt for a thermal relay with a current range of 90 to 120, in that case you still need a current transformer if you use a smaller thermal relay
The control circuit can be omitted. But the display instrument still needs to be connected to a current transformer.
The regulations require that installations with 55 kW or more must be equipped with it.
Installing a current transformer in the control circuit of a motor is used to measure the current flowing through the motor during operation, as well as to provide protection for certain relays, such as thermal relays. It is generally used in the control circuits of large-capacity low-voltage motors; a motor like the one mentioned by the original poster probably does not require it.
Of course, including those that are beneficial without any harm; we are simply considering cost savings.
Adding it would definitely be good; it can be used for protection as well as for instrument display.
This question was asked during an interview, and the interviewer believed it should be added, arguing that there is no corresponding overheat protector for such high currents. As I understand it, it can be decided depending on the circumstances; it’s not necessarily required.
Those of 55kw and above require installation
It is recommended that you install a current transformer; generally, for motors with a power rating of over 40 KW, it is necessary to have current display on site (although it is only a rough indication), as this is stipulated by the design requirements