Contactor-Type Transfer Switch with Electronic Motor Protection Relay

Last Updated on

CONTACTOR Transfer Switch

CONTACTOR Transfer SwitchGeneral Features

The Meiji Contractor-Type Transfer Switch (CTS) with EMPR gives you the convenience of using the same feeder lines for the load side during emergency power (generator), with a current-limiting device, the EMPR, that can give the user flexibility in adjusting the amount of power to be given each load, during power failures.


During normal power after a pre-set delayed time, the ‘MAIN’ contractor (please refer to the diagram) is energized, closing the circuit from the line side (MERALCO) to the load side (home, office, condo, unit, etc.). During this time, the electrical and mechanical interlocks of this 2-contractor system ‘locks-out’ and prevent the ‘GENSET’ contractor from energizing or closing.

Line wiring for single phaseDuring power outage (brownout), the ‘MAIN’ contractor is of course de-energized (opened), releasing the interlocks on the system. With the generator power on, after a pre-set delayed time, the ‘GENSET’ contractor will thus be energized and closes the circuit from the line side (generator), through the EMPR, to the load side. This time, the same interlocking system ‘locks out’ and prevents the ‘MAIN’ contractor from energizing or closing. A load user will be allowed to use the emergency power up to the pre-set limit of the EMPR.

Any overload will cause the EMPR to ‘trip’, thus cutting off any emergency power to that load. Depending on the size and setting of the EMPR, an overload can cause the emergency power to be cut-off from the load, in as short as 4 seconds. (Please refer to specifications on EMPR). Upon reduction of the said overload to the acceptable pre-set limit, emergency power may be restored back automatically to the said load.

When the normal power comes back, the ‘GENSET’ contractor is automatically de-energized, thus cutting-off the supply from the ‘GENSET’ to the load side, and releasing the mechanical and electrical interlocks of the system. At this point, the ‘GENSET’ is running at no-load and can be safely turned-off. After a pre-set delated time, the main contractor will be energized again, and normal power is then restored back.

Electronic Motor Protection Rleays – EMPR

The electronic motor protection relay, as named EMPR, protects electric equipments such as three-phase motors against overheating under normal and heavy starting conditions. The overheating can be caused by overloading, single-phasing or current unbalance etc.

Extensive current range

EMPR is available with continuous setting ranges for motor current between 0.2A and 90A. The current adjustable range is 5 times to 10 times.


This device makes a good performance in -25 degree C to 60 degree C in operation and in -50 degree C to 80 degree C in storage.


This device should be used in 10% RH to 90RH, and it’s recommended to be used in 60% RH.

Isolated Auxillary Contacts

EMPR has the isolated auxillary contacts, 1NO + 1NC

Test / Reset Button

The tripping function of the EMPR can be tested using the TEST/RESET button. EMPR can be activated by holding down this button.

Visible Indicator

The O.L. (Overload) LED and the fault trip LED indicate the trip situation caused by overload, phase loss and phase unbalance respectively.

Comments are closed.