13
Unit-Mounted Solid-State Starter (Optional) —
The 23XL chiller may be equipped with a solid-state, reduced-
voltage starter (Fig. 8 and 9). This starter’s primary function is
to provide on-off control of the compressor motor. This type of
starter reduces the peak starting torque, reduces the motor
inrush current, and decreases mechanical shock. This capabil-
ity is summed up by the phrase “soft starting.” The solid-state
starter is available as a 23XL option (factory supplied and
installed). The solid-state starters manufacturer name is located
inside the starter access door.
A solid-state, reduced-voltage starter operates by reducing
the starting voltage. The starting torque of a motor at full volt-
age is typically 125% to 175% of the running torque. When the
voltage and the current are reduced at start-up, the starting
torque is reduced as well. The object is to reduce the starting
voltage to just the voltage necessary to develop the torque re-
quired to get the motor moving. The voltage is reduced by sili-
con controlled rectifiers (SCRs). The voltage and current are
then ramped up in a desired period of time. Once full voltage is
reached, a bypass contactor is energized to bypass the SCRs.
There is a display on the front of the Benshaw, Inc., solid-
state starters that is useful for troubleshooting and starter
checkout. The display indicates:
•
voltage to the SCRs
•
power indication
•
proper phasing for rotation
•
start circuit energized
•
run state
•
software configuration
The starter is further explained in the Check Starter and
Troubleshooting Guide sections, pages 59 and 76.
Unit-Mounted Wye-Delta Starter (Optional) —
The 23XL chiller may be equipped with a wye-delta starter
mounted on the unit. This starter is intended for use with low-
voltage motors (under 600 v). It reduces the starting current
inrush by connecting each phase of the motor windings into a
wye configuration. This occurs during the starting period when
the motor is accelerating up to speed. Once the motor is up to
speed, the starter automatically connects the phase windings
into a delta configuration. Starter control, monitoring, and
motor protection is provided by Carrier’s Integrated Starter
Module (ISM).
When voltage is supplied to the solid-state circuitry, the
heat sinks in the starter as well as the wires leading to the
motor and the motor terminal are at line voltage. Do not
touch the heat sinks, power wiring, or motor terminals
while voltage is present or serious injury will result.
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6
LEGEND
Fig. 8 — Solid-State Starter Box,
Internal View
1
— REDISTART™Micro Input/Output Card
2
— Circuit Breaker 2 (CB2):
Machine Control and Heater Power
3
— Circuit Breaker 3 (CB3): Pumpout Unit
4
— REDISTART Micro Central Processing Unit Card (CPU)
5
— Restart Micro Power Card (hidden, not depicted)
6
— Restart Micro Bypass Card (hidden, not depicted)
Fig. 9 — Typical Starter External View
(Solid-State Starter Shown)