초록 ▼

Starting of single phase permanent magnet direct current motors in the desired direction of rotation is accomplished by providing a look up table stored in memory giving the correct sign or polarity of current for the angular position of the permanent magnet rotor of the motor. This stored look up t

Starting of single phase permanent magnet direct current motors in the desired direction of rotation is accomplished by providing a look up table stored in memory giving the correct sign or polarity of current for the angular position of the permanent magnet rotor of the motor. This stored look up table is developed by initially injecting current pulses of opposite polarity at different angular positions of the rotor, determining the difference between the rise times, and mapping the sign and the magnitude of the differences versus angular position. Thereafter, to start the motor in the correct direction, it is only necessary to inject current pulses of opposite polarity to know the angular position of the rotor and the polarity of the current required to start the motor in the correct direction. After the motor has been started, it is commutated by blanking the drive current at the zero crossings of the back emf. The current is turned off prior to a back emf crossing, and turned back on after the back emf crossing. The stored look up table tells how long to apply drive current before blanking because the table indicates how far away the zero crossing is, which is convened into the time remaining before blanking the drive current. Several embodiments of single phase motors are disclosed, as well as circuits useful for starting a motor and sensing back emf.

대표청구항 ▼

A method for starting and commutating a permanent-magnet, direct current motor having a single phase winding and having a corresponding look up table stored in a motor control circuit, said method comprising the steps of: injecting a first current pulse having a first polarity in the winding of the

A method for starting and commutating a permanent-magnet, direct current motor having a single phase winding and having a corresponding look up table stored in a motor control circuit, said method comprising the steps of: injecting a first current pulse having a first polarity in the winding of the standing motor, said first current pulse being long enough to effectuate an accurate measurement, but not so long that the motor moves; measuring the time required for the injected first current pulse to reach a predetermined magnitude thereby obtaining a first rise time; injecting a second current pulse having the opposite polarity in the winding of the standing motor, said second current pulse being long enough to effectuate an accurate measurement, but not so long that the motor moves; measuring the time required for the injected second current pulse to reach said predetermined magnitude thereby obtaining a second rise time; determining the difference between said first and second rise times; applying a drive current of the proper polarity to cause rotation of said motor in a preselected direction based upon the sign of the differences of the first and second rise times compared with the values in said look up table stored in said motor control circuit; using values in said look up table stored in said motor control circuit for locating pole position of the permanent magnet rotor of the motor; commutating the motor by providing timed drive pulses to the motor, said step of commutating comprising the following steps: turning off the drive current prior to a back emf crossing; sensing the back emf voltage when the drive current is turned off; turning the drive current back on after the back emf crossing; and using the sensed back emf voltage to generate timed ramp drive pulses.