About Starters; What A Starter Does - Trane Starters Engineering Bulletin

About Starters

What a Starter Does

Electric, centrifugal, water-cooled chillers use relatively large induction motors to drive the
compressors.These motors use a control device to connect to and disconnect from the electrical
power source.These control devices are referred to as combination controllers or, most commonly,
as motor starters. Variable-frequency drives or Adaptive Frequency™ Drives (AFDs) also serve as
motor starters, but their capabilities extend beyond starting and stopping the motor.
There are three main functions of the motor starter.The first function is to serve as the link between
the chiller's motor and the electrical distribution system. It is used during the starting and stopping
sequence.
Starting an induction motor from standstill causes a large electrical current draw for a few seconds.
The extra current is used to develop the required torque to get the compressor motor running at
full speed.The initial rush of current decreases as the compressor motor ramps up to full speed,
and is commonly referred to as inrush current.
The second function of the starter is to keep the initial current inrush below a specified level.Third,
the starter communicates with the unit controller to coordinate motor protection.
Starters can be as simple or as complex as necessary to meet various engineering specifications
and/or customer needs. A variable-speed drive can provide starter functions, among other things
(see
Remote-Mounted Adaptive Frequency Drive, " p.
purposes of this document.
Several voltage classes and starter types are available as indicated on the chart below. Each one
is described in greater detail in this document.
Table 1. Trane CenTraVac chiller starter choices
Low Voltage (208–600 V)
Remote-Mounted
Wye-Delta
Up to 1,700 amps
Solid-State
(Up to 1,120 amps with
disconnect or circuit breaker
required)
Adaptive Frequency
Drive
460/480/575/600 V
Up to
1,360 amps (460/480 V)
1,120 amps (575/600 V)
CTV-PRB004-EN
"Low Voltage—Unit-Mounted Adaptive Frequency Drive, " p. 25
Unit-Mounted
Wye-Delta
Up to 1,316 amps
(Up to 1,120 amps with
disconnect/circuit breaker
option)
Solid-State
(Up to 1,120 amps with
disconnect or circuit breaker
required)
Adaptive Frequency
Drive
Up to 1,210 amps
Circuit breaker standard
460–480 V
42). It will be classified as a starter type for the
Medium Voltage (2,300–6,600 V)
Remote-Mounted
Across-the-Line Across-the-Line
Up to 360 amps Up to 288 amps
Isolation switch, power Isolation switch, power
fuses standard fuses standard
Primary Reactor Primary Reactor
Up to 360 amps Up to 205 amps
Isolation switch, power Isolation switch, power
fuses standard fuses standard
Autotransformer Autotransformer
Up to 360 amps Up to 205 amps
Isolation switch, power Isolation switch, power
fuses standard fuses standard
Adaptive Frequency
Drive
Up to 250 amps
Isolation switch, power
fuses standard
and "Medium Voltage—
Medium Voltage
(10–13.8 kV)
Unit-Mounted Remote-Mounted
Across-the-Line
Up to 94 amps
Isolation switch, power
fuses standard
Primary Reactor
Up to 94 amps
Isolation switch, power
fuses standard
Autotransformer
Up to 94 amps
Isolation switch, power
fuses standard
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