Method and apparatus for controlling the speed of a single phase induction motor using frequency variation

An apparatus for controlling speed of a single phase induction motor, comprising:

• signal input means for inputting selected information regarding the single phase induction motor and outputting an operation start signal and a speed command signal in response thereto;
• control means for sequentially storing data representing sampled values of a sinusoidal wave signal and outputting said data in response to the speed command signal from said signal input means at an interval of a predetermined time period set by a timer;
• conversion means for converting said data from said control means into an analog sinusoidal wave signal having a desired frequency in accordance with said interval of said predetermined time period and outputting said converted sinusoidal wave signal at said desired frequency;
• triangular wave generation means for generating a triangular wave signal;
• comparison means for comparing said converted sinusoidal wave signal and said triangular wave signal and outputting a signal to control the speed of the single phase induction motor in accordance with said comparison;
• and
• inverter means for converting a DC voltage from a power source into a desired frequency of AC voltage in response to said control signal from said comparison means and outputting a drive voltage to the single phase induction motor in accordance with said converted AC voltage.

A method for controlling speed of a single phase induction motor using frequency variation, comprising the steps of:

• generating an operation start signal and a speed command signal according to a user's selection;
• outputting a digital data for formation of a sinusoidal wave signal of a desired frequency to converting means at an interval of a predetermined time period set by a timer to thereby generate the sinusoidal wave signal of the frequency desired by the user;
• generating said sinusoidal wave based on said digital data;
• comparing said sinusoidal wave with a triangular signal for controlling the speed of a motor;
• and
• converting a DC voltage from a power source into an AC voltage of a frequency band desired by the user to thereby operate the motor.