Controller for air conditioners and heat pumps

A speed controller for operating a single phase motor with power from a source providing first and second AC signals of frequency, f, with the first AC signal differing in phase from the second AC signal by approximately 180 degrees, the motor having a capacitor, an auxiliary winding connected to the capacitor, and a main winding, said speed controller comprising:

• a first means for combining said first and second AC signals and directing said combined signal through the main and auxiliary windings to operate the motor at a first speed, n1;
• a second means for generating third and fourth signals having frequency f/N, where N is an integer greater than one, with said fourth signal differing in phase from said third signal by 90 degrees and wherein said third and fourth signals are generated using selected half cycles from said first and second signals, and for disconnecting the capacitor from the auxiliary winding and directing said third signal through the main winding and said fourth signal through the auxiliary winding to operate the motor at a second speed, n2, with n2<n1;
• and
• means for switching between said first means and said second means to change the speed of the motor between said first speed, n1, and said second speed, n2.

A method for operating a single phase motor at a plurality of speeds, the motor having a capacitor, an auxiliary winding connected to the capacitor, and a main winding, said method comprising the steps of:

• providing first and second AC signals of frequency, f, with said first AC signal differing in phase from said second AC signal by approximately 180 degrees;
• combining said first and second AC signals and directing said combined signal through the main and auxiliary windings to operate the motor at a first speed, n1;
• generating third and fourth signals of frequency f/N, where N Is an integer greater than one, with said fourth signal differing in phase from said third signal by 90 degrees and wherein said third and fourth signals are generated using selected half cycles from said first and second signals;
• and
• disconnecting the capacitor from the auxiliary winding and directing said third signal through the main winding and said fourth signal through the auxiliary winding to operate the motor at a second speed, n2, with n2<n1.