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”

Equivalent Circuit

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

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

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

Example 6-1 continued

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

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

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.

Example 6-1 continued Phasor diagram for the new conditions

Example 6-1 continued

Example 6-1 continued

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

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