California Department of Transportation
 

8. RELAYS & SOLENOIDS

8.1 Circuit Transient Surges, Arc Suppression & Voltage Surge Protection

Protective devices shall be used to limit surge current (back EMF). All relay and solenoid coils shall have built-in or exterior mounted circuitry to limit surges. Such circuitry (e.g., diodes, resistor, varistor, zener-zener) shall be located at the coil.

8.2 Continuous Current

Derating of continuous current is dependent upon the load type. If a relay is used to switch a combination of loads, the dominant load shall be used for derating purposes.

8.3 Coil Energizing Voltage

The voltage to energize or trigger the relay shall be at least 110% of the minimum rated energizing voltage.

8.4 Coil Dropout Voltage

The voltage to dropout or un-trigger a relay shall be less than 90% of the maximum rated coil dropout voltage.

8.5 Shock-Vibration

Special mounting considerations are necessary for mechanical relays in high temperature or vibration environments. Relays shall not unintentionally switch even during worst case operating conditions.

Last updated 01/14/04