US 4,230,976 A · Brushless, permanent magnet d-c motor with improved commutation control

Abstract

Controlled semiconductor switches are inserted in series with the armature windings of the motor. To effect commutation when the difference between counter emf and applied voltage is small, that is, when the counter emf is high, so that commutation of armature current is effected during low, or no armature current flow, the control circuit includes circuit elements connected to and controlling current flow in the stator winding to considerably reduce the flow therethrough shortly before the theoretical commutation time, and increase current, or connect current to flow only shortly after the theoretical commutation time so that reliable commutation is effected. These circuit elements may, for example, be capacitors, R/C networks, artificial inductances, and the like, or circuits superimposing additional commutating signals derived directly from the induced counter emf, or by a separate sensing coil to the power supply for the commutating element.

Claims32

Dependent claims

Brushless d-c motor comprising a permanent magnet rotor (R) and stator winding means (2, 3, 110) and a Hall effect device (1) positioned to be controlled by magnetic flux from said permanent magnet rotor, the magnitude and direction of said flux being rotor position dependent, said Hall effect device providing in operation two output signals at its outputs,

electrical commutating device means connected to be controlled by the output signals of said Hall effect device to selectively connect said stator winding means (2, 3) to a source of power to generate, in operation, an alternating magnetic field,
means (Y, Y')to supply current to said Hall effect device (1), and
means (9) to modulate the Hall supply current supplied by said current supply means in synchronism with the rotor rotation to reduce said Hall supply current when the flux density at the Hall effect device is zero or in the neighborhood of zero, and to control said commutating device means to substantially reduce or interrupt the current flowing in said stator winding means at the instant when the flux density from the rotor (R) to which the Hall effect device is exposed is zero or in the neighborhood of zero.

Brushless d-c motor comprising

a permanent magnet rotor (R) and stator winding means (2, 3, 110),
a Hall effect device means (1) positioned to be controlled by magnetic flux from said permanent magnet rotor, the magnitude and direction of said flux being rotor position dependent and comprising at least two points of zero flux density per revolution,
said Hall effect device means providing, in operation, two output signals at its outputs;
d-c amplifier means (DA, DA';
140, 141;
142-147) connected to the Hall effect device means (1) for amplification of the output signals thereof;
electrical commutating device means (150, 151;
152, 153) connected to be controlled by the outputs of said device amplifier means to selectively connect said stator winding means to a source of power (P, N) to generate, in operation, a varying magnetic field;
a capacitative coupling element (6, 7, 106, 107;
158, 159) connected between each output of the Hall effect device means and the associated input of the associated commutating device means;
and
non-linear resistance means connected between each capacitative coupling element and the associated input of the associated commutating device means to introduce non-linearities in the signals applied to the commutating device means, the non-linear resistance means substantially reducing or interrupting the current flow in said stator winding means (2, 3, 110) when the flux density from the rotor (R) to which the Hall effect device means is exposed is zero and/or in the neighborhood of zero.

9 more elements

Brushless d-c motor comprising

a permanent magnet rotor (R) and stator winding means (2, 3, 110);
galvano/magnetic flux sensing means (1) positioned to be controlled by magnetic flux from said permanent magnet rotor, the magnitude and direction of said flux being rotor position dependent and comprising at least two points of zero flux density per revolution;
said galvanomagnetic flux sensing means providing, in operation, output signals at its output;
d-c amplifier means (DA, DA') connected to the galvanomagnetic flux sensing means (1) for essentially linear amplification of the output signals thereof;
electrical commutating device means (150, 151;
152, 153) connected to be controlled by the outputs of said amplifier means to selectively connect said stator winding means to a source of power (P, N) to generate, in operation, a varying magnetic field;
coupling elements (6, 7;
106, 107;
158, 159) connected between the output of the essentially linear amplifier and an associated input of the commutating device means;
and
non-linear resistance means connected between each coupling element and the associated input of the associated commutating device means to introduce non-linearities in the signals applied to the commutating device means, the non-linear resistance means substantially reducing or interrupting the current flow in said stator winding means (2, 3, 110) when the flux density from the rotor (R) to which the galvanomagnetic flux sensing means is exposed is zero or in the neighborhood of zero.

8 more elements

Dependencies are inferred from the claim text.

Brushless, permanent magnet d-c motor with improved commutation control

Life of this patent

Brushless, permanent magnet d-c motor with improved commutation control

Life of this patent

Abstract

Claims32