Single-Phase Compressor Motor Types - Tecumseh AH5540E Service Handbook

16
SERVICE HANDBOOK

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 dis-
tinctly different from the others. Each type of motor may have two to four different configurations
depending on the compressor components.
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
complete self-equalizing
tube systems such as household
refrigerators, freezers, small water
coolers, and dehumidifiers.
motor has a high resistance start
winding which
to remain in the circuit after the
motor has come up to speed (see
Figure 3-1). 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 (see Figure
3-2), or
• a module Positive Temperature
Coefficient (PTC) relay.
Capacitor Start — Induction
Run (CSIR)
The CSIR motor is similar to RSIR ex-
cept a start capacitor is included in
series with start winding to produce
a higher starting torque (see Figure
3-3). This is commonly used on com-
mercial refrigeration systems through
¾ HP . Two types of relays are used
with this motor:
• a current relay, or
• a potential relay.
Capacitor Start and Run (CSR)
This motor arrangement uses a start
capacitor and a run capacitor in paral-
lel with each other and in series with
the motor start winding (see Figure
3-4). This motor has high starting
torque, runs efficiently, and is used
on many refrigeration and air condi-
tioning applications through 5 HP . A
Line 1
Line 2
(115 Volt Only - Neutral)
Ground
Alt. 3/4" Thermal Protector
4 T M Thermal Protector
Line 1
capillary
Line 1
Line 2
Identi ed Conductor
(115 Volt Only - Neutral)
This
Line 2
Ground
(115 Volt Only - Neutral
is not designed
Ground
Compressor - Unit
FIGURE 3-1:
Alt. 3/4" Thermal Protector
Line 1
4 T M Ther mal Protector
Line 1
Line 1
Line 2
(115 Volt Only - Neutral)
Start Capacitor
Line 2
Ground
Line 2
Ground
(115 Volt Only - Neutral
Ground
Compressor - Unit
Compressor - Unit
FIGURE 3-2:
Line 1
Line 1
Alt. 3/4" Thermal Protector
4 T M Thermal Protector
Start Capacitor
Line 1
Line 2
(115 Volt Only - Neutral
Line 2
Line 2
Identi ed Conductor
(115 Volt Only - Neutral)
Ground
Ground
Ground
Compressor - Unit
Compressor - Unit
FIGURE 3-3:
Control
Compressor - Unit
Ground
External Thermal
Protector
Control
Control
Rela y - Current
)
Compressor - Unit
Ground
Ground
RSIR motor diagram with current
relay
External Thermal
Protector
External Thermal
Control
Protector
Control
Control
Relay - Current
Relay - Current
Compressor - Unit
)
Ground
Ground
Ground
RSIR motor diagram with wired-in
PTC relay
External Thermal
External Thermal
Protector
Control Protector
Control
Rela y - Current
Relay - Current
Control
C
)
S
Compressor - Unit
Ground
Ground
R
Ground
PTC Relay
CSIR motor diagram
External Thermal
External Thermal
Protector
C
S
R
PTC Rela y
C
C
S
S
R
R
PTC Relay
C
C
C
S
S
S
R
R
R
PTC Rela y
C
C
S
S
R
R