A method of operating a brushless motor having a stationary assembly with at least two different energizable windings for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields. The method includes the steps of simulating rotor position in accordance with the back emf condition of at least one winding, energizing a selected one of the windings in accordance with the simulated rotor position, sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time. An electrically commutated motor controller apparatus controls the speed of a variable speed motor compressor driven by an electrically commutated motor. A controller circuit includes a circuit for producing feedback signals representative of a back emf of the motor. A compressor speed circuit generates actual compressor speed signals from the feedback signals produced by the controller circuit. A duty cycle generator produces a speed control signal as a function of the actual compressor speed signals, and the speed control signal is transmitted to the controller circuit for adjusting the speed of the electrically commutated motor driven compressor. Other motor controls, refrigeration systems and methods of control and operation are also disclosed.

Motor controls, refrigeration systems and methods of motor operation and control

A sensorless control for DC permanent magnet brushless motor includes a feedback loop connected between the motor stator windings and the inverter which controls the timer at which current is provided to the various windings in sequence. The control of the invention includes a voltage sensing network for sensing the back EMF on each motor winding when it is unenergized and comparing this voltage with a null point. For maximum torque this voltage has an optimum value and variation from this value produces an error signal which is integrated to produce a VCO drive signal. This signal controls the frequency of a VCO which in turn controls the switching times of the inverter.

Back EMF sampling circuit for phase locked loop motor control

A control apparatus detects a suitable starting point during rotational oscillation of a rotor at the start of a brushless motor by combining the polarity of a counter electromotive force generated in an armature coil of an armature winding of the brushless motor for a nonexcited phase due to the rotational oscillation of the rotor (when armature coils for particular phases are excited at the start of the brushless motor) with the pulse edge of an excitation switchover signal obtained from the potential of a neutral point of the armature winding having the armature coils connected in star-connection and that of a neutral point of a detecting resistance circuit having resistors connected in star-connection. Each of the resistors of the resistance circuit is arranged in parallel with a corresponding one of the armature coils the armature winding. By driving the brushless motor from the detected suitable starting point, it is possible to effect smooth and quick control of the starting operation of the brushless motor.

Control apparatus for brushless motor

A single phase permanent magnet motor includes a rotor, a stator, and a quadrature axis winding positioned out-of-phase from a main winding of the stator for generating an output signal representative of rotor angular position. An integrator can be coupled to the quadrature axis winding for phase retarding the output signal, and a comparator can be coupled to the integrator for detecting zero crossings of the phase retarded output signal to provide a commutation signal. The quadrature axis winding can be positioned about ninety electrical degrees out-of-phase from the main winding of the stator, and the integrator can be adapted to phase retard the output signal by a number of degrees which decreases as a speed of the motor increases. At low speeds the phase retard is preferably at about ninety degrees so that the phase retarded signal becomes in-phase with the main stator winding back EMF voltage. The motor may further include a rectifier coupled to the quadrature axis winding for rectifying the output signal, and a lowpass filter for filtering the rectified output signal to provide a signal proportional to velocity. Also the single phase motor is commutated for maximum torque production.

Quadrature axis winding for sensorless rotor angular position control of single phase permanent magnet motor

A control apparatus for an elevator comprising a temperature sensor which senses the temperature of the rotor of an induction motor during the stoppage of a cage, and a voltage/frequency control device which calculates the secondary winding resistance value of the induction motor on the basis of the output value of the temperature sensor and which vector-controls a power conversion device by the use of the calculated secondary winding resistance value, so that during the stoppage of the elevator, the temperature of the rotor is measured to alter the secondary winding resistance value necessary for the vector control, whereby the optimum control can be performed.

Control apparatus for elevator

A transducerless brushless permanent magnet motor in which a signal induced by the rotor in an unexcited winding is used to sense the rotor position. The sensed voltage, induced in the winding by the rotor, is integrated to provide a representation of the magnetic flux coupling the rotor and winding. Before start-up, both the rotor position and the integrator are initialized to align the circuit representation of the flux with the actual flux. In an additional embodiment of the invention, a self-initialization circuit is provided to automatically preset the rotor and flux integrator to pre-determined and corresponding values.

Self-starting transducerless, brushless D.C. motor controller

A method of measuring induction motor parameters so that the speed and torque control of an induction motor controller may be optimized. While the motor is stopped, a test signal made up of a current pulse of a known amplitude is applied to one or more windings of the motor stator for a selected period of time, after which the current pulse is turned off. After a short delay, the instanteous voltage across the stator windings is measured, and also an integration of the stator voltage is started which continues long enough so that the stator voltage decays to substantially zero. The measured voltage and integrated voltage are respectively proportional to the rotor resistance and the motor magnetizing inductance.

Adaptive induction motor controller

An AC motor drive includes a power converter which supplies current to a DC bus from three-phase power lines. An inverter drives the motor from power delivered to the DC bus and it regenerates power to the DC bus when the motor is decelerated. The power converter in turn regenerates the power to the power lines by controlling line current such that it is substantially in-phase with the applied line voltages. Current overload protection is provided for the transistor switches employed in the power converter bridge circuit.

Line-regenerative motor controller with current limiter

An AC motor drive includes a power converter (10 to 53) which supplies current to a DC bus (3) from three-phase power lines (4, 5, 6). An inverter (2) drives the motor (1) from power delivered to the DC bus (3) and it regenerates power to the DC bus (3) when the motor (1) is decelerated. The power converter (10 to 53) in turn regenerates the power to the power lines (4, 5, 6) by controlling line current such that it is substantially in-phase with the applied line voltages. Current overload protection (60 to 64) is provided for the transistor switches (16 to 21) employed in the power converter bridge circuit.

Donald E. Fulton

Papers

Self-starting transducerless, brushless D.C. motor controller

Adaptive induction motor controller

Line-regenerative motor controller with current limiter

A power converter for a motor control system