An electronic meter for measuring the saving in electrical power

In electrical installation and building services engineering the power factor is a major consideration in efficient building or system operation. It is the measure of how effectively your equipment is converting electric current from power generation network to useful power output. Your industry can save money and gain other benefits when your power factor is high enough to avoid power factor surcharges on your electricity bills. For this purpose, this work presents an electronic circuit for the measurement of electrical energy. The design is based on a sample and hold method, which generates two DC signals. The first signal is proportional to the peak value of the line voltage, Vm and the second signal is proportional to the instantaneous value of the line current at the instant of peak voltage, Vm., i.e. Im cos Φ, where Φ is the phase angle between the line voltage and line current signals. Multiplication of the two signals over a predetermined period of time will provide an output proportional to the electrical energy consumed by the load. A voltage to frequency converter, VFC, is used to digitize the electrical energy signal. This signal is then digitally displayed through suitable circuitry. Results are presented to show the effect of a changing power factor on the power available at a constant current and the annual cost savings that can be made.