Harnessing a Back-EMF

An overview of the EMF Lenz's law states that: the current induced in a circuit due to a change in a magnetic field is directed to oppos...

An overview of the EMF

Lenz's law states that: the current induced in a circuit due to a change in a magnetic field is directed to oppose the change in flux and to exert a mechanical force which opposes the motion.

Counter-electromotive force (counter EMF, CEMF), also known as back electromotive force (back EMF), is the electromotive force or "voltage" that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday's law of induction, electromagnetic induction, Lenz's law).

A method of achieving high efficiency of energy usage includes passing current through an inductor, causing the current to be repeatedly interrupted, thereby generating a back emf in the inductor and thereafter harnessing the back emf so generated to supply energy to an energy receiving or processing device. The frequency of interruptions should be 40 Hz or more and is achievable by applying rectifying means to the current. The invention extends to apparatus for harnessing such back-emf and energy generating means comprising an inductor and current interruption means connectable to an energy receiving device.

Power supply for electrical resistance operated installations and appliances

A power supply is provided for an electrial installation or appliance presenting a resistive load (1, 8, 12, 19, 40). The power supply has electrical input means for connection to a supply of electrical energy and output means for connection to a suitable resistive load and is characterized in that electronic switching means (3, 9, 13, 25, 26) is provided for switching the electrical power supply to the output means on and off at a switching frequency of at least about 100 Hz is embodied therein. The power supply thus creates a series of cycles each having an "on" and an "off" component with a duty cycle of from about 3 percent to about 90 percent. The power supply optionally includes one or more inductors (4, 10, 11, 18, 23, 24, 37,38, 39), as may be necessary, to provide, together with the resistive load, a circuit inductance.; The circuit includes means, typically diode means that may be inherently present in the switching means, for ensuring that any back emf or transient energy generated across the inductance is dissipated across the resistive load or is fed back to the power supply source, or both, during the "off" component of the duty cycle. The switching frequency, duty cycle, and inductance in the power supply are chosen so as to cooperate with the resistive load to provide a required operation of the resistive load and generally an enhanced efficiency when compared to the efficiency thereof in the absence of the said power supply.