Page 96 - Electromechanical Devices and Components Illustrated Sourcebook

58 Electromechanical Devices & Components Illustrated Sourcebook

Chassis Ground Run/Off
Switch
Output Fuse
Input Fuses
Start
Button

Control
Transformer Emergency
120 VAC Stop

Enclosure
240/480 VAC
Coil Terminals Sensor Loop

MOTOR RESET
STARTER
120 VAC COIL
Motor
Power
(240/480 VAC)
Heater Set
Contactor
Figure 4-67 Commercial Motor Controller with Sensor Loop

This is the function of the start button, which bridges the vides a fault indicator in the event a sensor shuts down the
sensor loop. system.
Figures 4-68 and 4-69 show a control circuit for a com- Another common use for contactors is in reversing circuits.
mercial screw compressor. This particular unit is designed to A three-phase motor can be reversed by simply reversing two
operate either continuously or in an automatic mode and pro- of the power wires. By using two contactors side-by-side, a

Motor Controller (From Page 9-5)
240/480 VAC
Three Phase

C L Power
M

Motor
Control
Relay
Fault L

On/Off/Auto
Switch Over Pressure
Low Oil Pressure

Over Temperature
T
Delay Off
Pressure Emergency Stop
Switch
Figure 4-68 Three-Phase Motor Control Circuit Diagram with Run/Automatic Mode,
Sensors, and Fault Indicator Lamp