Abstract: A circuit and method for controlling a current level in a switched reluctance motor phase coil are provided. The circuit includes a current sensor for generating a current indicative signal indicative of a level of current in the phase coil and first and second comparators for comparing the current indicative signal to upper and lower hysteresis band limit signals. The circuit further includes a drive circuit, such as a flip-flop, for generating a drive signal responsive to the first and second comparators and first and second switches disposed on either side of the phase coil for providing current to the phase coil. The first switch is responsive to the drive signal and a phase control signal to maintain the current in the coil within the hysteresis band defined by the upper and lower hysteresis band limit signals.

Abstract: A method for controlling a motor and a circuit for implementing the method are provided. The method includes the steps of providing current to a first phase coil of a motor and measuring the time for the current to rise between two predetermined levels. Because current rise time is proportional to phase inductance, and therefore, rotor position, the measured current rise time can be compared to a desired current rise time to determine whether conduction intervals in the motor phases are in-phase with the position of the rotor or are lagging or leading the position of the rotor. The method finally includes the step of supplying current to one of the first phase coil and a second phase coil responsive to the measured rise time in order to bring subsequent conduction intervals into phase with the position of the rotor.

Abstract: A circuit and method for controlling a switched reluctance motor are provided. The circuit includes a phase coil and a switch that controls a current in the phase coil responsive to a hysteresis control signal. The circuit also includes a current sensor that measures the level of current in the phase coil and a comparator that compares the measured current level to a predetermined upper hysteresis current level. The circuit further includes a hysteresis control signal generating circuit that generates the hysteresis control signal responsive to the comparison signal and a timing signal that comprises a series of timing pulses. The hysteresis control signal assumes a first logic level whenever the measured level of current in the phase coil exceeds the predetermined upper hysteresis current level, thereby opening the switch and allowing current to dissipate from the phase coil.

Abstract: A switched reluctance motor drive includes a noise reduction circuit configured to control the decay of current when a motor phase is switched from active to inactive. The current decay is controlled to occur in two stages: a first portion and a second portion. The first portion is controlled by alternately activating and deactivating one of the two switches in the two switch drive topology to obtain a current profile conforming to a predetermined profile. The current decay in the second portion of the inactive interval occurs by keeping both switches off so that it decays naturally. The duration of the first portion of the inactive interval is different for each motor phase, as is the duty cycle of the switch gating signal driving the switch that is alternately activated and deactivated. The scheme reduces the acoustic noise generated during operation of the motor.

Abstract: A method and circuit for controlling a switched reluctance motor are provided. The method includes the steps of controlling a current in a phase coil of a motor phase of the motor during an active stage of the motor phase and controlling the current in the phase coil during an inactive stage of the motor phase. The latter step includes the substep of increasing the level of current in the phase coil for a predetermined period of time during the inactive stage of the motor phase. By increasing the current level during the inactive stage, the rate of current dissipation is reduced, thereby reducing acoustic noise. A circuit in accordance with the present invention includes a pair of one-shot circuits connected together in series and responsive to the end of the active stage of the motor phase. The second one-shot circuit generates an output signal that closes a switch connected to a phase coil of a motor phase of the motor for a predetermined period of time during the inactive stage of the motor phase.

Abstract: An apparatus for controlling a switched reluctance machine changes the operating modes between a single-phase operating mode, and a multi-phase operating mode. The switched reluctance motor includes a rotatable rotor, a stator, and a plurality of stator windings defining a corresponding plurality of machine phases. When in the multi-phase mode, all of the plurality of stator windings corresponding to the plurality of machine phases are energized. When in the single-phase mode, stator windings corresponding to a single, selected machine phase are energized. The apparatus includes a logic circuit for sensing a speed of the rotor and generating a speed signal in response thereto, and a comparator circuit.

Abstract: An apparatus and method for generating electrical signals which are representative of the rotational position of a rotor relative to a stator and for controlling commutation in a variable reluctance electric motor includes a circuit for generating relatively small pulses of electrical current to a non-energized stator winding of the motor. As the rotor rotates relative to the stator, the inductance induced in such stator winding will vary. As a result, the magnitude of the current pulses in the stator winding will increase over time. When the magnitude of such current pulses exceeds a predetermined threshold level corresponding to a predetermined relative rotational position of the rotor, a signal is generated to cause commutation of the motor. Variations in the inductances of the stator windings are compensated for by providing maximum and minimum voltage detector and hold circuits which are responsive to the output signals from the sample and hold circuit.

Abstract: A phase current sensing apparatus is disclosed for use in a bifilar-wound switched reluctance motor drive topology. The phase winding includes a primary coil, and a secondary coil. A power switch is connected in-series with the primary coil, and a common node, which common node is further connected to ground by way of a resistive shunt. The other end of the primary coil is tied to a positive bus of a power supply. The secondary coil, which is oppositely wound relative to the primary coil, has one end tied to the positive bus, and the other end tied to a cathode terminal of a diode. An anode terminal of the diode is tied to the common node. A non-inverting amplifier, and an inverting amplifier are provided and each is responsive to the voltage developed on the common node. The non-inverting amplifier generates a first signal S.sub.1 that is indicative of a primary coil current. The inverting amplifier generates a second signal S.sub.2 that is indicative of a secondary coil current.

Abstract: An apparatus for controlling commutation of a three-phase variable reluctance machine includes a sensor, a sampling circuit, an inductance waveform generating circuit, a phase advance circuit, a threshold signal generating circuit, and an output comparator. The sensor includes a stack of several laminations which are identical to the motor laminations that form the motor stator, and is mounted at one end thereof. The motor includes a plurality of stator windings forming a plurality of corresponding machine phases. The sensor also includes a plurality of sensor windings electrically isolated from the stator windings. Each sensor winding is associated with a corresponding stator winding. Each sensor winding also has an inductance characteristic that varies according to an actual position of the rotor.

Abstract: A method of operating a switched reluctance machine is disclosed, which provides electrical current overload protection. The stator winding motor drive employs a high-side semiconductor switch, along with a corresponding high-side gate driver (which incorporates a bootstrap-type drive circuit). A low-side semiconductor switch, and a corresponding gate driver is also used to thereby define a two-switch per phase topology. The high-side MOSFET switch gate driver must have rising, and falling edges from an associated controller in order for the bootstrap drive power supply portion to function. A drive controller is configured so that it will generate these rising, and falling edges only when the motor is moving, as indicated by a speed signal. Therefore, if the motor stops moving, due to an unexpected load, such as a seized pump connected to an output shaft thereof, the speed signal will so indicate the stall, wherein the controller will not generate a signal having rising and falling edges.

Abstract: An average current measuring circuit (40) in accordance with the invention includes a first switch (42) connected between a pair of reference potentials which has a duty cycle which is controlled by a control signal which pulse width modulates current flowing through the switch to a load and varies the current flowing through the switch in frequency; a first current transformer (44) coupled to the current flowing through the first switch for producing an output signal proportional to the current flow; a sampling circuit (46), coupled to the output signal, for sampling current magnitude when the switch is turned on; and an averaging circuit (60) coupled to the sampling circuit, for producing an average signal of successive samples of a current flow through the load.