1. Phase-Splitting Split-Phase Induction Motor
Main Winding contributes “Direct-Axis” flux, d
Auxiliary Winding contributes “Quadrature-flux”, q
Auxiliary Winding is also known as the “Starting Winding”

2. Equivalent Circuit

3. Purpose of the “Phase-Splitter”
Make the current in the Auxiliary Winding out of phase with the current in the Main Winding.
This results in the quadrature field and the main field being out of phase.
The locked-rotor torque will be given by

4. Example 6-1
The main and auxiliary windings of a hypothetical 120 V, 60 Hz, split-phase motor have the following locked-rotor parameters:
Rmw=2.00 Ω Xmw=3.50 Ω
Raw=9.15 Ω Xaw=8.40 Ω
The motor is connected to a 120 V system. Determine

5. Example 6-1 continued
The locked-rotor current in each winding

6. Example 6-1 continued

7. Example 6-1 continued
The phase displacement angle between the main and auxiliary currents

8. Example 6-1 continued
The locked-rotor torque in terms of the machine constant

9. Example 6-1 continued
External resistance required in series with the auxiliary winding in order to obtain a 30 phase displacement between the currents in the two windings.

10. Example 6-1 continued
Phasor diagram for the new conditions

11. Example 6-1 continued

12. Example 6-1 continued

13. Example 6-1 continued
Locked-rotor torque for the condition in d

14. Example 6-1 continued
% increase in locked-rotor torque due to the adding of additional resistance