Our extensive studies and research have disclosed and verified that all brush commutating BDC motors have a ‘build-in’ encoder which due to the laws of physics induces voltage transient signals on the power supply wires to the motor when it rotates.

Referring to the figure the voltage transients extracted from the power supply wires to the motor are:

• Ref 1: The primary transient – the Back-Fire or Kick-Back transient which we call the ‘Counter Spike’ is induced by the collapse of the magnetic field in a coil of the motor for each commutation and is seen as a high voltage spark between the breaking contact points.

• Ref 2: The secondary transients – we call them the ‘Impedance Spikes’ and are induced every time a brush opens and closes a coil circuit. We therefore have two impedance spikes for every commutation of the motor.

Using these transients (spikes) as encoder signals will reveal precise physical points in the motors commutations from start to stop and whether the motor is powered on un-powered (i.e. whether the motor runs as a motor or is coasting in generator mode).



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