The p.f. controller monitors the phase displacement between current and voltage. Because the phase displacement angle changes with the load of the motor, this measurement method is ideal for the monitoring of asynchronous motors for underload and no-load operation, independent of size. However, in some cases, the p.f. ? barely changes if the load of the motor changes, e.g. in the case of relatively minor load changes on large-scale motors, single-phase split-pole motors or collector motors.

The p.f. ? controller monitors single and three-phase asynchronous motors up to approx. 5 A (without current transformer) for underload and no-load operation. This is phase-sequence-independent and increases plant availability. Typical applications are fan monitoring in the case of V-belt breakage, pump monitoring in the event of valve closure or dry runs. A current transformer is used for higher rated currents.

If the value falls below the p.f. value set at the p.f. controller for the duration of the set response delay, the output relay switches to the alarm state and the red LED lights up. If it exceeds the p.f. value, the output relay switches back without any significant delay.

• Adjustable p.f. response value, from 0 to 0.97
• Current range up to 8 A
• LED display for operation and alarm
• Automatic resetting of alarm.