Figure 14-27.Schematic wiring diagram
of a capacitor-start capacitor-run
high starting torque and is used with hermetic
systems up to 5 horsepower.
The permanent split-phase motor has
limited starting torque and is used basically
w i t h c a p i l l a r y t u b e a i r - c o n d i t i o n i ng
equipment, such as window units. Capillary
systems permit high-side and low-side
pressure equalization when the compressor is
not operating. A run capacitor is wired in
series with the starting winding. Both the
starting winding and the run capacitor remain
in the circuit during operation. No start
relay or start capacitor is needed. Figure 14-
28 is a schematic wiring diagram of the
circuits used in this type of motor.
WINDINGS AND TERMINALS
Split-phase motors used in hermetic
refrigeration and air-conditioning applications
are designed to start under load. These split-
phase and capacitor motors use two sets of
spiral windings: a starting winding and a
running winding. The two sets of windings
differ in their impedance and in their
positions in the stator slots.
The starting winding has high resistance
and small reactance, whereas the running
winding has low resistance and high reactance.
Reactance is the opposition to the flow of
alternating current by inductance and
capacitance. The running winding has many
turns of large wire and is placed in the
bottom of the stator slots. The starting
winding is wound of small, high resistance
wire and is placed on top of the running
winding. Both windings are connected
internally at one end to provide a common
lead, and when starting, both are energized in
parallel. The currents are out of phase with
each other and their combined efforts
produce a rotating field that starts the motor.
Figure 14-29 shows the starting and
running windings of a two-pole motor in their
90-degree out-of-phase positions.
Figure 14-28.Schematic wiring diagram
of a permanent split-phase motor.
Figure 14-29.View of a two-pole motor
having starting and running windings.