TM 5-4310-362-14
Section II. COMPONENT FUNCTION
4-3.
ELECTRIC MOTOR CONTROLS
The electric motor controls consist of the pressure switch and the motor starter. These controls make the operation of the
air compressor fully automatic.
ELECTRIC MOTOR CONTROLS SCHEMATIC
NORMAL OPERATION, PRESSURE BELOW 160 PSI
Power from the main power switch comes into the starter at L1 and L2. If the pressure in the air tank is below 160 psi, the
switch contacts will be closed. Current will then go through the coil. The coil then pulls the normally open contacts E1
and E2 closed. The circuit to the motor is completed and the motor starts.
NORMAL OPERATION, PRESSURE ABOVE 180 PSI
When pressure goes above 180 psi the contacts of the pressure switch open and stop the current through the coil.
Contacts E1 and E2 open and the motor stops.
OVERLOAD CONDITION
If the motor draws too much current, overload relay OL melts and the normally closed contacts in series with the coil open
up. This tops the current through the coil and contacts E1 and E2 open. This stops the motor and prevents it from
burning out. The relay has to be manually reset before the motor can be started again.
4-2
