Low-voltage Circuit BreakersMolded Case Circuit Breakers
No-fuse Circuit Breakers
Used for electric circuit protection and open/close of low-voltage circuits (600VAC or less, 750VDC or less).
No-fuse circuit breaker is the name that Mitsubishi Electric uses for its molded case circuit breaker.
Tripping
Tripping occurs in these situations.
Features
Can open and close safely
Can perform breaking repeatedly
Can break multiple electrodes at once
Attachments can be installed
Tripping Method
Thermal-electromagnetic type
Tripping by means of a bimetal and electromagnetic force
- Time-delay tripping operationWhen overcurrent flows, the bimetal becomes overheated, bending in the direction shown by the arrow and moving the trip bar.
- Instantaneous tripping operationWhen large current flows, the moving iron piece moves in the direction of the arrow, moving the trip bar.
Hydraulic-electromagnetic type
Tripping by means of electromagnetic force
- Time-delay tripping operationWhen overcurrent flows, the electromagnetic force exceeds the force of the braking spring, causing the moving iron core to gradually move, attracting the moving iron piece and moving the trip bar. Delay characteristics are obtained by the viscous resistance of the silicon oil.
- Instantaneous tripping operationWhen a large current flows, the moving metal piece is attracted instantaneously, moving the trip bar without waiting for the moving iron core to move.
Electronic type (example)
Tripping based on calculations in an electronic circuit
- The current flowing to each phase is transformed by the CT, and full-wave rectification of each phase is performed by the rectifier circuit. After rectification, the current peak conversion and effective value conversion circuits select the maximum phase of the converted currents.
- When overcurrent or large current flows, the timing circuits operate according to the maximum current, and the trigger circuit outputs the trigger signal. This excites the trip coil and activates the open/close mechanism.
In particular with the electronic type, the rated current value can be adjusted, making it extremely convenient for achieving coordination as well.
When the optional setting device (Y-360) is used, it is possible to easily check the operation and monitor/set the characteristic settings.
Connection Type
A variety of connection types are available, front connection type, rear connection type, and plug-in type.
You can order the type that matches your needs.
Front connection type
This is the standard type that can be connected from the front.
Rear connection type
Wiring from the back of the circuit breaker is possible.
Plug-in type
The circuit breaker itself is inserted into a plug-in terminal block. This type contributes to shorter work times.
