C-mac® module type RP91 is used for power monitoring of 1-phase and symmetrical 3-phase loads, f.inst. motors.
RP91 can be connected directly to loads with nominal current consumption up to 6 A; If the current is bigger, a standard current transformer is used.
The unit is supplied with an adjustable start-up delay, which ensures that the output relay is activated independant of the load, when the motor is started. RP 91 is supplied for both over- and underload monitoring.
The module is monitoring the total power consumption (U x I x cos ) which gives a much higher sensitivity than it is possible with the RP81.
The setpoint is coarse adjusted on a 10-position switch, and fine-adjusted on a potentiometer in front of the unit, which gives a very high sensitivity on the adjustment function.
When the setpoint is reached, an adjustable time-delay on 0,1 to 30 seconds starts. After this period, the relay releases, on the condition that the load has been higher than the setpoint in the whole period, in this way it is ensured, that the relay will not release in case of short changes in
the power consumption.
In order to get the most accurate setpoint adjustment, especially when very small loads are monitored, the unit is supplied for 4 different current ranges, and all units are available with inverted function, to detect underloads.