Motor circuit breakers

Motor circuit breakers

Motor circuit breakers are used to switch on and protect electric motors against short-circuits, overloads and phase asymmetry. Thus, they play an important role in automation control circuits and electrical systems.

• three dimensions up to 100A
• rotary and changeover design
• high short-circuit capacity
• full range of accessories
• housing with IP66 protection
• external rotary drive option
• possibility of connection with contactors

MMS type motor circuit breakers are produced in 3 housing sizes and switch off currents up to 100 A, which means protection of 3-phase motors up to and including 45 kW. Circuit breakers can also protect single-phase motors by appropriately connecting the three-phase system in series. The devices contain two releases: thermal class 10 (motor overload protection) and electromagnetic (short-circuit protection).
The operating characteristics of the short-circuit release are set to the multiplicity of the current of 13xIe - this gives the reliability of operation in many types of motor operation and allows for very heavy starts. The switches are also temperature-compensated and their operation can also be checked through the test function. LS motor protections are characterized by very high electrical parameters. Depending on the version and rated current, they have a short-circuit capacity of up to 100 kA.
MMS motor circuit breakers for the 32 model (MMS-32) have 16 current ranges of the thermal member and are available in two versions of the actuator that switches the device on:
- rotary drive (MMS-32H),
- changeover drive (MMS-32S).
The advantage of the changeover drive is its depth, which is 75 mm and allows for use in modular cabinets. The second MMS-63 model is designed for motors with 63 A current (9 current ranges of the thermal element). As one of the few manufacturers, LS offers motor switches of one more current size MMS-100 to 100 A (10 thermal protection ranges).

The following accessories are available for MMS switches:
- front mounted auxiliary contacts FX (2xNO, 1xNO, 1xNC, 1xNC);
- LX auxiliary contacts (2xNO, 1xNO, 1xNC, 1xNC) mounted on the side;
- alarm contacts of the LA switch actuation;
- alarm contacts of the LAM magnetic element actuation;
- RS growth trigger;
- RU undervoltage release;
- RUX undervoltage release with auxiliary contact;
- MEH rotary drive for the cabinet facade;
- two- and three-row PB connecting combs;
- EPH enclosure with IP65 protection degree;
- DA adapters for connecting the circuit breaker with the contactor;
- MU mounting bases for the starter kit.
The motor circuit breaker is an important safety element, not only to protect the motors, but also to protect the personnel. In the MMS type, there are a number of possibilities which additionally improve safety, ranging from a simple lock of the drive against switching on the circuit breaker, through the trip test function, ending with additional options in the form of shunt (RS) and undervoltage releases (RU) and alarm contacts (LA). Front-mounted (FX) or side-mounted (LX) auxiliary contacts are also available as options for the circuit-breakers. A very interesting solution is also the rotary drive to be mounted on the cabinet door. Possible rod lengths are 115 and 315 mm. For solutions where a higher degree of protection is required, the EPH housing with IP65 protection is available, in which the MMS-32H switch with a shunt release can be mounted.