Variable speed controller for air moving applications using an AC induction motor

A control system for an AC induction motor having a main winding and an auxiliary winding comprising:

• a) a capacitor in series with the auxiliary winding;
• b) a first triac for connection in series with the auxiliary winding and capacitor for controlling application of line voltage to the auxiliary winding and the capacitor,
• c) a second triac for connection in series with the main winding for modulating application of line voltage to the main winding;
• d) a command module connected to the first triac for switching the first triac on and off without modulating application of line voltage to the auxiliary winding;
• and
• e) the command module further connected to the second triac for regulating motor speed;
• f) the command module further including circuitry for determining motor speed from induced voltage when line voltage is turned off by the first and second triacs;
• and
• g) at least one of a temperature sensor and a pressure sensor connected to the command module.

An air treatment system having at least one variable speed AC induction motor with a main winding and an auxiliary winding, comprising:

• a) a controller for an AC induction motor comprising:
• i) a capacitor in series with the auxiliary winding,
• ii) a first triac for connection in series with the auxiliary winding and capacitor for controlling application of line voltage to the auxiliary winding and the capacitor without modulating application of line voltage to the auxiliary winding;
• iii) a second triac for connection in series with the main winding for modulating application of line voltage to the main winding;
• b) a command module having inputs to the controller for regulating the controller;
• the command module connected to the first triac for switching the first triac on and off without modulating application of line voltage to the auxiliary winding;
• the command module further connected to the second triac for regulating motor speed;
• c) sensing apparatus including at least one of a pressure sensor, a motor speed sensor, and a temperature sensor, the at least one of a pressure sensor, a motor speed sensor, and a temperature sensor having an input to the command module, whereby the command module regulates the controller to vary the speed of the motor according to the input from the at least one of a pressure sensor, a motor speed sensor, and a temperature sensor.