Overview

This section discusses specific cases when inductive loads at output points require additional protective circuits (directly on the actuator) and provides two examples of protective circuitry.

Case 1

When there are contacted circuit elements (e.g. for safety interlocks) in the output conductors.

Case 2

When the leads are very long.

Case 3

Where inductive actuators are operated via relay contacts of the I/O base (to extend contact life and for EMC considerations).

Protective Circuit Types

In all three cases, the protective circuit is a clamping diode.

The following table provides generic selection guidelines.

Type of Load

Suppression Device

Minimum Component Rating

DC circuits

a reverse-biased clamping diode across the load

2 A and greater than twice the maximum load voltage

Consult relay and contactor manufacturers’ catalogs for commercial suppression devices matched to your particular products.

Example 1

An example of a protective circuit for inductive DC actuators is illustrated below:

K1 contact, e.g., for safety interlocks

V1 clamping diode as the protective circuit

Example 2

Another example of a protective circuit for inductive DC actuators is illustrated below:

V2 clamping diode as the protective circuit