Brushless D-C motor with several Y connected phase windings

Claim 1

In a brushless d-c motor with several Y connected phase windings which are coupled to a d-c source through a commutating arrangement including controlled semiconductor elements, each phase having one end coupled to a controlled semiconductor element and to one terminal of a pickup diode, the pickup diodes having their other terminals coupled to a common tie point, a voltage dependent element having one terminal coupled to the common tie point and another terminal coupled through a series resistor to a neutral point, the load circuit of a controlled semiconductor switching element being shunted across the voltage dependent element and the series resistance with the actual speed value taken off through a smoothing member including at least a resistor and a capacitor, the improvement comprising: (a) a first additional transistor having its base coupled to the neutral point; (b) a first resistor coupling the junction point between the voltage dependent element and series resistor to the emitter of said first additional transistor; and (c) a forward biased diode and series resistance coupling the collector of said first additional transistor to ground whereby a speed proportional current pulse can be picked up at the junction point between said diode and said series resistance.