CTV-PRB004-EN 81
Glossary
Trip unit
Device that opens the operating mechanism within the
circuit breaker in the event of a prolonged overload or
short-circuit current. To accomplish this, an internal
electronic rating plug is provided, which tells the trip unit
when to open the mechanism. Rating plugs are factory
set within specific ranges to meet motor performance
requirements and are field-adjustable.
U
Unit controller
The microprocessor controller mounted on the chiller. Also
referred to as the control panel.
Vacuum break
Contacts that are encapsulated in an evacuated, ceramic
bottle. Since the contacts operate in a vacuum, arcs are
quickly extinguished because there are no ionized gases
present to support conduction. The claimed advantages
are no contact maintenance, long contact life and safety,
since there is no exposed arcing. All medium- voltage
starters used by Trane have vacuum break contactors.
Vacuum break contactors are used typically only on
medium-v
olt
age starters.
V
Voltage
The following voltages apply to CenTraVacs:
The electrical power industry refers to 2,000 through
69,000 volts as medium voltage.
Voltage monitoring relays, overvoltage relay
A relay and an adjustable line voltage monitor that will
stop the chiller if the line voltage exceeds a preset value.
This overvoltage monitoring system is a lock-out type that
requires manual reset at the starter.
The chiller controller provides under/overvoltage
protection
as
standard.
Voltage monitoring relays, undervoltage relay
A nonadjustable relay that is powered directly by line
voltage. If line voltage drops below 55 percent nominal
volt
age, the undervoltage relay will stop the chiller. This
relay requires a manual reset at the starter.
The chiller controller provides under/overvoltage
protection as
standard.
Voltage monitoring relays, adjustable undervoltage
relay
A relay and an adjustable line voltage monitor that will
stop a chiller if line voltage drops below a preset value.
This undervoltage monitoring system is a lock-out system
that requires manual reset at the starter.
The chiller controller provides under/overvoltage
protection
as
standard.
W
Wattmeter
A device that displays instantaneous power (watts) in the
form of a dial meter or a digital display. When a wattmeter
is ordered for a starter, the wattmeter option includes all
necessary transformers.
Watt-hour demand register
An option on a watt-hour meter that indicates the total
power used per time period (i.e., 15 minutes). The value
display
ed is proportional to the electrical energy used in
the unit's time period. The watt-hour demand value will
only increase when the power demand in a new time
period exceeds the power demand in any previous time
period; thus, the demand register indicates the largest
power demand in any time period. The demand register
may be manually reset to zero to monitor a new series of
time periods.
Watt-hour meter
A device that measures and registers the cumulative
amount of electrical energy used in terms of watt-hours
(or kilowatt-hours). This is a standard feature on the unit
control panel.
When a watt-hour meter is ordered for a starter, this
option
includes
all necessary transformers.
Watt-hour meter pulse initiator
A device that generates pulses (contact closures)
proportional to a definite energy value (watt-hours per
pulse). Output contacts of pulse initiators are normally
connected to pulse-operated demand recorders or used to
feed energy consumption information to computers and
load controllers.
When ordering pulse initiators, the type of pulses and the
pulse
rate
the end devices will accept must be indicated.
Withstand rating
See “Short-circuit current rating (SCCR)”, p. 79.
Control Voltage 120 Vac
Lo
w Voltage 208–600 Vac
Medium Voltage 601–13,800 Vac
CTV-PRB004.book Page 81 Sunday, December 18, 2011 6:39 PM
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