Retrofit RPM Vacuum Circuit Breaker

Vacuum circuit-breaker and integral carriage

There are 5 current ratings of circuit breaker available, having ratings of 630/800A, 1250A, 2000A, 2500A and 630A cap switching.

The circuit-breaker is mounted on a steel carriage, having four flanged wheels to facilitate location within the enclosure. A central screw mechanism operated by a removable handle is provided for raising and lowering the circuit-breaker.

The RPM-series LMVP circuit breaker has 3 separate dough moulded resin housings containing the three vacuum interrupters which are air insulated and separated by perspex phase barriers. Primary through bushings are also incorporated in the housing and at their upper end accommodate self-aligning multi-finger isolating contacts. Guide pins are fitted to the top plate to ensure correct location of the circuit breaker, and a copper contact provides positive earthing of the unit. The LMVP vacuum circuit breaker is interchangeable with the Reyrolle Switchgear LMT oil circuit breaker.

The housing has moulded inserts which provide accurate and simple location of components. The main operating shaft is coupled to the moving contacts of the interrupters through a drive insulator. Current transfer is through multi-laminated sliding contacts and the added contact load in the closed position is provided by disc springs.

Copper-chrome contact material is used in the interrupters to minimise contact erosion. The added contact load spring assembly gives indication that the erosion limit has been reached.


The circuit breakers have been type tested to mechanical endurance class M2 – IEC 62271-100.

Safety Interlocks

Safety interlocking fully complies with IEC 62271-200 and includes the following extra features:
(a) Tripping by attempted isolation.

Operational Interlocks

Mechanical interlocks protect the operator and the equipment by preventing the following operations:
(a) Moving the circuit breaker into housing unless fully lowered.
(b) Raising the circuit breaker unless the secondary circuit plug is correctly inserted into the carriage socket and secured.
(c) Inserting or removing the secondary plug unless the circuit breaker is fully lowered and the locating bolt free.
(d) Closing the circuit breaker if the manual trip is pushed.
(e) Discharging the closing spring when the breaker is closed.
(f) Attempted isolation does not trip the circuit breaker in service.