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Molded Case Circuit Breakers

Low Voltage Circuit Breakers

Low Voltage Circuit Breaker is used for protection and open/close of electric circuit of low voltage circuit (1000VAC or less, 1500VDC or less).



MCCB will trip when overload or short-circuit occurred.

Automatic Tripping Devices

There are 3 types of Thermal-Magnetic Type, Hydraulic-Magnetic Type and Electronic Type.

Thermal-Magnetic Type

Thermal-Magnetic Type image

Trip with the power of bimetal and electromagnet.

  1. An overcurrent heats and warps the bimetal to trip by rotate the trip bar.
  2. If the overcurrent is excessive, movable core rotates clockwise and the armature is attracted and to trip by rotate the trip bar.

Hydraulic-Magnetic Type

Hydraulic-Magnetic Type image

Trip with the power of electromagnet.

  1. At an overcurrent flow, the magnetic force of the coil overcomes the spring, the core closes to the pole piece, attracts the armature, and actuates the trip bar. The delay is obtained by the viscosity of silicon oil.
  2. If the overcurrent is excessive, the armature is instantly attracted, without the influence of the moving core.

Principle of Electronic Trip Relay Operation

Principle of Electronic Trip Relay Operation.

Trip with the calculation of electronic circuit.

  1. The current flowing in each phase is detected by a current transformer (CT). Each phase of the transformed current undergoes full-phase rectification in the rectifier circuit. After rectification, each of the currents are converted by a peak-conversion and an effective-value conversion circuit.
  2. When over current or short circuit current flows, each time-delay circuit generates a time delay corresponding to the largest phase. The trigger circuit outputs a trigger signal. The trip coil is excited, operating the switching mechanism to trip.

Especially, electronic type is very convenient for cooperation, as the rated current value is adjustable.
By using optional setting device (Y-350), simple operation check and monitoring / setting of characteristic setting value are available.


Various connection methods such as Front connection type, Rear connection type, Plug-in type, etc. are available.
You can order according to your needs.

Front connection type

Standard type connectable from the front.

Front connection type

Rear connection type

Wiring from the backside of the circuit breaker is available.

Rear connection type

Plug-in type

Insert the main body into the plug-in terminal block.

Plug-in type