Single Phase Motors Flashcards
Where are most single phase motors found?
Rural and residential applications.
What is the typical efficency rating of a single phase motor?
60%.
How does a resistance split phase motor operate?
By using two stator windings of differing resistance and inductance to create an out of phase magnetic field rotation.
{Sometimes called a resistance start motor}
What are most resistance split phase rotors constructed of?
Cast aluminum squirrel cage around a laminated core.
What are three methods of start winding cut out?
Centrifugal switch;
Current sensitive relay;
Triac (electronic switch).
What is the typical displacement of the main and start winding currents in a resistance start motor?
25 to 30 degrees.
When do the centrifugal switch contacts open?
75% of rated speed.
How does a single phase motor operate when the start winding is cut out?
By cross field theory.
How many poles do most split phase motors have?
4.
What is the most common size of split phase motor?
1/4 hp.
What does reversible mean?
Direction of rotation can be changed at a standstill.
What does reversing mean?
Able to change direction of rotation in the run condition.
What are five common uses of resistance split phase motors?
Forced air furnace;
Washing machine;
Small drill press;
Fan;
Sump pump.
Why do split phase motors have such a low starting torque?
Because the winding currents only differ by roughly 30 degrees.
What are typical capacitance values for a 1/2 hp 2 value capacitor motor?
300 uf start;
40 uf run.
