Operating instructions

25
Mechanical and electrical design
36
0301
Relays
The EX 12 and 22 models employ eight relays.
Construction
The body of the relay holding the stationary
contacts is made of current-resistant plastic. A
solenoid and a contact bank hold the moving
contacts. The contacts are spring-loaded to
assure the correct contact pressure.
The relay is constructed for continuous
operation, whether mounted horizontally or
vertically.
Screw-type terminals provide perfect connections
even when one or two wires have different
diameters.
Operation
When the solenoid is energized, the two halves
of the magnet core are drawn together, pulling
down the moving contacts, thus making or
breaking the circuit. When the current cuts out,
springs force the contact bank into its original
position, thus closing or opening the circuits.
Trouble shooting
If the relay fails to operate despite power to the
coil, turn off the power and check the solenoid by
measuring the resistance across the terminals
(1).
If the relay hums when power is applied, this
indicates either a break in the insulator holding
the moving contacts at the axle where it holds
the top half of core (3) or a rusty core (4), which
can be cleaned.
Make sure that the moving contact assembly (4)
moves freely. Always replace burnt or pitted
contacts (2)... do not reuse contacts.
Fig.
36