Low Voltage Switching Gears

Magnetic Contactor

Magnetic switch

A combination of a magnetic contactor and a thermal overload relay is called a magnetic switch in the industry. Mainly used in motor (motor load) switching applications.

Frame size

Indicates the size (dimensions) of the magnetic contactor. Basically, the outer dimensions increase as the rated operational voltage and rated operational current increase.

Rated capacity (kW)

The maximum rated output (kW) during motor operation at the rated operational voltage.

Rated operational voltage (V)

The maximum load voltage that satisfies the switching capacity, switching frequency, and contact service life.

Rated operational current (A)

The maximum load current that satisfies the switching capacity, switching frequency, and contact service life at the rated operational voltage.

Rated carry current (AC-1)

The maximum switching current that can be applied when the contact is not switching. In addition, load conditions that assume resistive loads, such as heaters, are called AC-1.

Rated carry current (AC-3)

Load conditions set assuming a 3-phase cage motor. This is the reference load condition when switching the motor with a magnetic contactor.

Auxiliary contact

Contacts that operate in conjunction with the main contacts. Auxiliary contacts have a switching capacity lower than that of the main contacts, and are used for sequence circuits such as signal and self-holding circuits.

Mirror contact

Mirror contact is a mechanism found mainly in contactor. With the combination of the main circuit and the auxiliary circuit of the main unit, welding the main contacts will result in a structure that secures a shock resistance voltage of 2.5 kV or more, or a contact interval of 0.5 mm or more, for all b-contacts of the auxiliary circuit contacts even if the excitation of the coil is released. The main contact may also be turned ON when the auxiliary circuit is welded. Even with the combined usage of the auxiliary contact unit (J73KC-AM), welding the main contact in the main unit will create a mirror contact construction where the attached auxiliary contact (b-contact) is opened.

Thermal Overload Relay

Bimetallic strip

A special metal that curves when heat is applied. The property of this metal is used for the overload detection function in thermal overload relays.

Setting current

The current value that determines the operation of the thermal overload relay that is the standard for the rated operational current. Generally, it is set to the same value as the rated current value of the motor. When a current exceeding the set setting current continuously flows in the thermal overload relay, it is detected and the circuit is cut.

Phase failure protection function

This function detects an open circuit and activates a thermal overload relay to protect the motor from burnout.

Cold-start characteristics

Thermal overload relay characteristics from the off status until the thermal overload relay trips.

Hot-start characteristics

Thermal overload relay characteristics from normal operation (when the rated current flows in the thermal overload relay) until the thermal overload relay trips.

Manual reset and auto reset methods

The manual reset method sets manual return after the thermal overload relay trips. The auto reset method sets automatic return after the thermal overload relay trips.

Trip class 10A

This is an operating characteristic in which motor circuit operation when overload occurs (hot start) takes less than two minutes at 150% Ie, and operation when locking occurs (cold start) takes less than two to ten seconds at 720% Ie in accordance with IEC 60947-4-1. (Ie is setting current.)

Manual Motor Starter

Trip class 10

This is an operating characteristic in which motor circuit operation when overload occurs (hot start) takes less than four minutes at 150% Ie, and operation when locking occurs (cold start) takes less than four to ten seconds at 720% Ie in accordance with IEC 60947-4-1. (Ie is setting current.)

Type 1, Type 2 harmonized protection

When a short-circuit current flows in a combination of short circuit protection devices (SCPD), such as magnetic switches and overcurrent circuit breakers, the current is interrupted by the short circuit protection device. If the combination is not properly selected, the magnetic switch contacts and thermal overload relay heater element may be damaged by the electromagnetic force or energy of the short-circuit current. IEC 60947-1 and JIS C 8201-1 provide types of harmonized protection according to the degree of damage to the magnetic switch during a short circuit. The short-circuit current is evaluated using "assumed short-circuit current 'r' " and "conditional rated short circuit current Iq" defined by the manufacturer.
Type 1: Damage to magnetic switch or heater is observed. Requires partial or complete replacement at the time of inspection.
Type 2: No damage except light welding of the magnetic switch. Can remain in use without replacement at the time of inspection.

Utilization category Cat.A

This category of circuit breaker has no deliberate short-time delay in the operation of short circuit conditions for other other circuit breakers in series on the load side.