Most motor protection relies on current. For many of the problems that matter most, such as a pump running dry or a lightly loaded conveyor jamming, current is the wrong signal. True motor power is the right one.
An induction motor draws a large share of its full-load current even when it is doing almost no work, because much of that current magnetises the motor rather than driving the load. As the load rises from zero, the power factor improves sharply while the current hardly changes. On a typical motor the current reading moves very little until the load reaches about half of full load.
True power is volts multiplied by amps multiplied by the power factor. Because it takes the power factor into account, it rises in proportion to the work the motor is doing, with the same sensitivity at light load as at full load. On a pump, low flow means low power and high flow means high power, so the power reading tells you what is happening to the fluid.
Load Controls sensors measure current and voltage and calculate true power continuously. The Universal Power Cell family uses Hall effect sensing, which is not disturbed by unusual wave shapes or low frequencies, so it works on the output of a variable frequency drive as well as on fixed-speed, single-phase and DC motors. Most models are self-contained, with no separate current or voltage transformers to install, and they mount in the motor control cabinet rather than in the pipework or the hazardous area.
Tell us the application, the motor power in kW, the supply voltage and whether the motor runs on a variable frequency drive. We will recommend the right model and send a quotation.
