Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1982-01-04
1983-07-26
Smith, Jr., David
Electricity: motive power systems
Induction motor systems
Primary circuit control
318778, H02P 142
Patent
active
043956718
ABSTRACT:
The present invention utilizes the fact that the rate of change of the amplitude of a sinusoidal waveform is substantially constant within an interval of such waveform near its zero crossing. A circuit for measuring peak amplitudes of sinusoidal waveforms includes a voltage differentiator for differentiating between a first and second reference selected within the interval of a sinusoidal waveform wherein the rate of change of the amplitude is substantially constant; a time interval calculator for measuring a time interval between the references; a frequency determinator for determining the frequency of oscillation of the waveform; and a processing unit responsive to the voltage differentiator, the time interval calculator, and the frequency determinator for determining a peak amplitude of the waveform. In accordance with the present invention, a method of controlling the operation of an induction motor of the type having a main winding and at least one start winding utilizes the circuit for measuring peak amplitudes of sinusoidal waveforms. The motor start control system includes a current sensing device for producing a waveform proportional to the main winding current of the motor and a control circuit responsive to the waveform for deenergizing the start winding of the motor when the amplitude of the waveform is less than a threshold level wherein the threshold level is variable in accordance with the start main winding current. By continuously determining peak amplitudes of the waveform which is proportional to main winding current of the motor and storing an initial peak amplitude of the waveform, the start winding is deenergized when a peak amplitude of the waveform becomes less than a defined percentage of the stored initial peak amplitude.
REFERENCES:
patent: 3731152 (1973-05-01), Rockefeller, Jr.
patent: 3758763 (1973-09-01), Nohara et al.
patent: 3764871 (1973-10-01), Scheuer et al.
patent: 4047082 (1977-09-01), Scheuer et al.
patent: 4073009 (1978-02-01), Andow et al.
patent: 4249117 (1981-02-01), Leukhardt et al.
Scheuer et al., "An Adjustable-Threshold Electronic Motor Starting System", 1976 IEEE Appliance Technical Conference; Purdue Univ., West Lafayette, Ind., Apr. 29-30, 1976.
Bristol Robert G.
Sandler Louis M.
Emhart Industries Inc.
Gomes David W.
Meyer Robert F.
Smith Jr. David
LandOfFree
Control system and method for motor starting does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control system and method for motor starting, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control system and method for motor starting will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2223844