Page 103 - Electromechanical Devices and Components Illustrated Sourcebook

Chapter 4 Electrical Controls 65

Field Terminal

Resistors

Switched Wiper
Switched Contacts

Links

Solenoid Coil

Sense Terminals Dash Pot
Pivot
Return Spring

Rheostat
Common

Voltage Adjustment
Damping Adjustment
Figure 4-83 Sector Relay as a Voltage Regulator

Field Supply
Figure 4-85 shows a sector relay configured for communi-
cation applications. This type of relay was used on early dial
telephone systems. Each time a pulse is sent to the advance
solenoid, the wiper advances one position. If the number six
was dialed, then six pulses would be sent to the relay and the
Resistors wiper would advance six positions. These relays carry a reset
solenoid that rotates the reset plate which, in turn, lifts the
advance and hold ratchets. The return spring then resets the
wiper back to zero.
Solenoid
Switched
Contacts
Output Voltage
Adjustment Latching Relays
Latching relays are relays that can be switched and remain
switched after power has been released. To switch the relay
Output back, a second coil must be momentarily energized.
Figure 4-86 shows a latching knife switch relay. When the
upper solenoid is energized it pulls the blade into the upper
contacts. The contacts hold the blade in position even after the
Field Winding solenoid has been de-energized. To switch the relay the lower
Generator solenoid is energized and the blade is pulled into the lower
Figure 4-84 Voltage Regulator Schematic contacts.