Control circuit for an synchronous electric motor of the brushless type
AssigneeC.E.SET. S.r.l.
InventorPasqualino Riola'
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Abstract
A control circuit comprises a TRIAC (T) in series with the stator winding (1) of the motor across the terminals of an alternating voltage source (V.sub.M). A fixed sensor (H) is associated with the rotor (R) and operable to provide a signal indicative of the magnetic polarity of the part of the rotor (R) facing it. A diode circuit (DC) including at least one Zener diode supplies the sensor (H) and provides a signal indicative of the polarity of the alternating supply voltage (V.sub.M). A driver circuit (PC) is connected to the sensor (H) and to the diode circuit (DC) and pilots the control input (g) of the TRIAC (T) in a predetermined manner in dependence on the instantaneous position of the rotor (R) and the polarity of the supply voltage (V.sub.M).
Claims16
A control circuit for a brushless synchronous electric motor including a permanent magnet rotor (R) rotatable between stator pole pieces (5, 6) shaped in such a way to define, with respect to the rotor (R), an air gap (7) of non-uniform width such that the rotor (R) at rest is disposed in a predetermined angular position (.alpha.) and upon start-up has a preferential direction of rotation;
- the control circuit being characterised in that it comprises, in combination
- a bi-directional static switch (T) in series with the stator winding (1) between the terminals (M, N) of an alternating voltage source (V.sub.M);
- signal generator circuit means (Z1, Z2;
- Z0;
- Z3) operable to provide a signal indicative of the polarity of the alternating voltage source (V.sub.M);
- a fixed electric sensor (H) associated with the rotor (R) to provide a signal (V.sub.h) indicative of the polarity of the part of the rotor (R) facing it;
- and
- a driver circuit (PC) connected to the sensor (H) and to the signal generator circuit means (Z1, Z2;
- Z0;
- Z3) and arranged to provide a control signal for controlling the conduction at a control terminal (g) of the switch (T) in a predetermined manner in dependence on the position of the rotor (R) and the polarity of the alternating voltage source (V.sub.M).
Dependencies are inferred from the claim text.