Full Voltage AC magnetic two speed controllers are designed to control reconnectable squirrel-cage induction motors for operation at two speeds depending on the construction of the motor. These controllers are available in combination and non-combination types.
The speed of an induction motor is a function of the supply frequency and the number of poles of the motor winding. To obtain different speeds with a fixed supply frequency, the number of magnetic poles of the motor must be changed.
Characteristics at any speed are similar to those of a single-speed motor. There are two basic methods of providing multiple pole combinations:
- Separate-Winding Motors have a separate winding for each speed. This motor construction is slightly more expensive, but the controller is relatively simple, and a wide variety of speeds can be selected. Separate winding motors with delta connected motor windings require one corner to be opened on each unused winding.
- Consequent-Pole Motors have a single winding for two speeds. Extra winding taps are brought out for reconnection for different numbers of stator poles. While the motor costs less, the controller is more complicated, and speed range is limited to a 2-to-1 ratio.
- 5-pole starter and 3-pole starter horizontally interlocked
- Size 0-4, 2 starters horizontally interlocked
- Size 5, 2 starters with vertical mechanical interlock
- Available in 200V and increasing
- Compatible overload relay
- NEMA 1-4X or EEMAC or GE enclosures
- Fusible Switch or Breaker Combinations
- Solid state Overload available
- Surge repressor, extra starter auxiliary contacts vary per starter
- Push to “Start” and “Stop”
- CSA and UL inspection available
- Refer to specification downloads for exact ratings