Abstract: A device determines the mean power absorbed from a current supply by measuring the current in a phase, and the voltage between two phases, determining the product thereof, and integrating the product.A first potentiometer provides a proportion of the voltage which is an image of the current, and subtracts it from that voltage between phases. A second potentiometer provides a proportion of the voltage between phases and subtracts if from the product. A third potentiometer provides a proportion of a constant voltage and subtracts it from that product. The third potentiometer is adjusted so that the output power of the integrator shall be zero when the motor rotates under no-load condition.