C-mac® module type RP81 is used for load monitoring of 3-phase motors, as the phase angle (cos ) between motor current and -voltage changes in proportion to the mechanical load of the motor. You will see the biggest change in phase angle, if the motor is loaded between 0 and 60% of nominal load, which makes the RP81 suitable for monitoring of V-belts, pumps running dry, etc.
RP81 can be connected directly to motors with nominal current up to 6 A. If the current is bigger, you use a standard current transformer .
