|
Load classification |
Supply type |
Application |
Switching with relay |
|
AC1 |
AC single-phase
AC three-phase
|
Resistive or slightly Inductive AC loads. |
Work within the relay data. |
|
AC3 |
AC single-phase
AC three-phase
|
Starting and stopping AC three-phase of Squirrel cage motors.
Reversing direction of rotation only after motor has stopped rotating.
Three-phase:
Motor reversal is only permitted if there is a guaranteed break of 50ms between energisation in one direction and energisation in the other.
Single-phase:
Provision of 300ms “dead break” time when neither relay contacts are closed - during which time the capacitor discharges harmlessly through the motor windings. |
For single-phase:
Keep to the relay data.
For three-phase:
See “Three-phase motors” section. |
|
AC4 |
AC three-phase |
Starting, Stopping and Reversing direction of rotation of Squirrel cage motors. Jogging (Inching). Regenerative braking (Plugging). |
Not possible using relays. Since, when reversing a phase connection, severe contact arcing will occur.
|
|
AC14 |
AC single-phase |
Control of small electromagnetic loads (<72 VA), power contactors, magnetic solenoid valves, and electromagnets. |
Assume a peak inrush current of approx. 6-times rated current, and keep this within the specified “Maximum peak current” for the relay. |
|
AC15 |
AC single-phase |
Control of small electromagnetic loads (>72 VA), power contactors, magnetic solenoid valves, and electromagnets. |
Assume a peak inrush current of approx. 10-times rated current, and keep this within the specified “Maximum peak current” for the relay.
|
|
DC1 |
DC |
Resistive loads or slightly inductive DC loads. (The switching voltage at the same current can be doubled by wiring 2 contacts in series). |
Work within relay data (see the diagram “Maximum DC1 breaking capacity”). |
|
DC13 |
DC |
Control of electromagnetic loads, power contactors, magnetic solenoid valves, and electromagnets. |
This assumes no inrush current, although the switch off over-voltage can be up to 15 times the rated voltage. An approximation of the relay rating on a DC inductive load with 40 ms L/R can be made using 50 % of the DC1 rating. If a freewheeling diode is wired in parallel to the load, it can be considered the same value as DC1. See the diagram “Maximum DC1 breaking capacity” |