Trane ctv-prc007-en manual Reliability, Operation, Features

Unit	Unit Mounted
Options	Starter (Cont.)

•System Design Time Cost Savings System design time is reduced, since all starter components and interconnecting wiring are pre- engineered and selected.

•Complete package available with Agency Approval

•Application

The Trane unit mounted starter can be applied on low voltage (600 volts) and below applications up to approximately 1300 tons capacity. To determine the unit mounted starter to be used with a particular selection, it is necessary to know the current draw of the compressor motor. The starter current draw must be greater than, or equal to, the compressor motor current draw.

•Reliability

The unit mounted starter is a star-delta closed transition electromechanical starter. Motor starters of this configuration have proven reliability in thousands of centrifugal chiller applications around the world. The proven electromechanical concept plus the use of industrial quality components makes the CenTraVac unit mounted starter dependable in all kinds of service applications.

Operation

The unit mounted starter is a star (wye) delta, closed transition, reduced voltage starter. When starting and during acceleration, the motor is connected in its wye configuration. Because of this arrangement the voltage applied to the

motor windings is reduced to one divided by the square root of three or

0.58 times line voltage. This reduction in

winding voltage results in a reduction in

inrush current. The inrush current is 0.33

times the full voltage locked rotor current

rating of the motor. The accelerating

torque of the motor is also reduced to

0.33 times the full voltage torque rating.

This is sufficient to fully accelerate the

compressor motor. The unit control

panel monitors motor current during

operation via current transformers

located in the starter enclosure. When

during acceleration the line current

drops to approximately 0.85 times rated

load current, transition is initiated. The

closed transition feature provides for a

continuous motor current flow during

transition by placing resistors in the

Figure O-1 – Typical Equipment Room Layout – Conventional Remote Star-Delta Starter

Figure O-2 – Typical Equipment Room Layout – Unit-Mounted Star-Delta Starter

circuit momentarily. This prevents

buildup of damaging torques to the

system during this period. With the

completion of transition, the motor

windings are connected in the delta

configuration with full line voltage.

Three precision current transformers monitor phase current. Contactor position and various voltage signals provide extensive interlocking between the starter and the microcomputer in the CenTraVac™ control panel. All logic and subsequent instruction originate in the unit control panel. Protection against the following starter defects is provided:

•High motor current (starting and running)

•Improper starter circuitry

•Excessive accelerating time

•Incomplete starting sequence

•Loss of phase

•Phase amperage unbalance

•Phase reversal

•Distribution fault

Features

The Trane CenTraVac Unit Mounted Starter includes the following standard features:

•NEMA 1 enclosure, designed to accommodate padlock

•3 KVA control power transformer with

120V secondary

•Fused 120V control circuit

•3-phase incoming line terminals

•6 output load terminals factory- connected to the motor

14 CTV-PRC007-EN