Method of Wiring - for Three Phase DOL Motor
The Main contactor has three NO contacts and one NO and
NC Auxiliary contacts. A thermal overload relay is shown
in the example but one can use only a contactor without
the overload unit. If a thermal overload unit is used,
it's rating should correspond to the motor running amperage.
Install the 415 V coil contactor in a suitable enclosure
and fix the On/Off Push Button switches at the required
Wire from a 3 Phase power supply of a 3 Pole MCB or a
Main switch of the Power Distribution to the L1,L2 and
L3 terminals of the contactor. If a Thermal overload is
connected to the contactor's T1,T2 and T3 terminals, then
connect the load wires to the motor to the T1,T2 and T3
terminals of the thermal overload.
Now for the control wiring.
Connect a wire to L1 terminal and connect the other end
to a terminal of the On Push Button.
Connect the other terminal of the On Push Butto to the
terminal of the Off Push button.
The remaining therminal of the OFF Push button should
be wired to one of the Thermal Overload's NC contact terminal.
The other terminal of the Thermal Overload's NC contact
should be wired to the coil terminal A1 of the contactor.
[ If a Thermal overload is not used, then the remaining
therminal of the OFF Push button should be wired to A1
terminal of the contactor.]
Connect the A2 terminal to L2 terminal of the contactor.
Wire from NO Auxiliary contact terminals of the contactor
to On Push Button's Terminals.
Now energize the 3 Ph. supply to the contactor. Pressing
the On button momentaraly will energize and hold the contactor
until pressing Off Push button . Any overload will be
detected by the Thermal overload and will open up the
NC contact. Until manually reset it, the circuit will
not be energized even when the On Push button is pressed.
[ Wiring - for Single Phase DOL Motor starting is almost
similar but the coil voltage is 230 V. Please see Single
Phase DOL (Direct On Line) Starting PDF File.