16
Chapter 3
I.
Single Phase Compressor
Motor Types
Tecumseh hermetic compressors contain motors
designed for specific requirements of starting torque
and running efficiency. There are four general types
of single phase motors, each distinctly different from
the others. Each type of motor may have two to four
different configurations depending on the compres-
sor components.
A. Resistance Start—Induction Run (RSIR)
This motor, also known as a split-phase motor, is
used on many small hermetic compressors up
through 1/3 HP. The motor has low starting torque
and must be applied to completely self-equalizing
capillary tube systems such as household refrigera-
tors, freezers, small water coolers, and dehumidifi-
ers. This motor has a high resistance start winding
which is not designed to remain in the circuit after
the motor has come up to speed. A relay is necessary
to perform the function of disconnecting the start
winding as the motor comes up to design speed.
Three types of relays are used with this motor:
•
a current relay,
•
a wired-in Positive Temperature Coefficient
(PTC) relay, or
•
a module Positive Temperature Coefficient
(PTC).
B. Capacitor Start—Induction Run (CSIR)
The CSIR motor is similar to RSIR except a start
capacitor is included in series with start winding to
produce a higher starting torque. This is commonly
used on commercial refrigeration systems through
3/4 HP. Two types of relays are used with this
motor:
•
a current relay, or
•
a potential relay.
Figure 3-1.
RSIR motor diagram with current relay.
Line 1
Line 2
Ground
Control
Relay - Current
External Thermal
Protector
Star
t
Winding
Main
Winding
Compressor - Unit
Ground
C
S
R
Figure 3-2.
RSIR motor diagram with wired-in
PTC relay.
4 T M Thermal Protector
Identified Conductor
(115 Volt Only - Neutral)
Line 1
Line 2
Ground
Star
t
Winding
Main
Winding
PTC Relay
Compressor - Unit
Ground
Alt. 3/4" Thermal Protector
Control
C
S
R
Figure 3-3.
CSIR motor diagram.
Line 1
Line 2
Ground
Control
Relay - Current
External Thermal
Protector
Star
t
Winding
Main
Winding
Compressor - Unit
Ground
S
R
C
