CTV-PRB004-EN
19
Low-Voltage Starter Types
Starting sequence
1. The “start” signal from the CenTraVac controller energizes the pilot relay (PR).
2. The PR contacts close to energize the star contactor (S).
3. The S contacts close to connect the motor in the star configuration.
4. An S interlock closes to energize the start contactor (1M).
5. The 1M contacts close to connect the motor to the line.
6. A time delay relay or current monitoring device initiates transition by energizing the resistor
contactor (1A).
7.
1A contacts close to connect the resistors to the line in the star configuration and in parallel with
the compressor motor.
8. A 1A interlock now opens to de-energize the S contactor.
9. The S contacts open to connect the resistors and motor windings in series in the delta
configuration.
10. An S interlock closes to energize the run contactor (2M).
11. The 2M contacts close to bypass the resistors and connect the compressor motor directly to the
line in the delta configuration.
Dimensions
The typical unit-mounted wye-delta starter size is shown in
Figure 9, p. 20
. Typical remote-
mounted one-, two- and three-door starter sizes are shown in
Figure 10, p. 20
,
Figure 11, p. 20
, and
Figure 12, p. 21
. Always consult the submittal drawings for as-built dimensions.
Figure 7.
Simplified wye-delta wiring schematic
WYE-DELTA
STARTER WIRING
LINE
VOLTAGE
OL
OL
OL
1M
1M
1M
1M
1M
R
R
R
2M
2M
PR
2M
2M
2M
1A
1A
1A
1A
1A
S
S
S
S
S
S
F
F
CPT
START-
STOP
PR
TRANSITION
MOTOR
CTV-PRB004.book Page 19 Sunday, December 18, 2011 6:39 PM
