Instruction Book
Effective: November 2017
Page 45
IB131016EN
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5-5.2 RATING PLUG
All trip units use a fixed type rating plug. The current
rating of the rating plug must match the current
rating of the current sensors (Figure
5-19
and Table
5.2).
The rating plug performs several functions:
1) It tells the trip unit what the rating is of the current
sensors. A label on the front of the rating plug clearly
indicates that the rating plug and sensors must have
the same rating.
2) It determines the maximum instantaneous
setting which is a function of the current sensor
rating.
If the rating plug is removed from the trip unit, the
circuit breaker will trip if it is carrying current. Make
certain the rating plug is secured in position with its
retaining screw.
Do not torque the retaining screw
beyond 15 In-Oz.
Refer to Table
5.2
for a tabulation of the available
rating plugs.
5-5.3 CURRENT SENSORS
Three current sensors are installed at the rear of
the cassette on the lower terminals. The sensors
produce an output current proportional to the load
current. Under pre-selected conditions of current
magnitude and time, the sensors furnish the trip unit
with a signal and the energy required to trip the
circuit breaker.
Table 5.2 Current Sensors and Matching Rating Plugs
Current Rating in Amperes
100 200 250
300 400 600
630 800 1000
1200 1250
1600
2000 2500
----
Neutral current sensors are available for customer
installation. The additional sensor is not supplied
with the circuit breaker and must be ordered
separately. They are wired to the trip unit through
the secondary contacts of the circuit breaker.
Zero sequence transformers (vectorial summation)
are available with a 100:1 and 200:1 tap ratio.
Refer to Table
5.2
for a tabulation of the available
current sensor ratings.
5-5.4 TRIP ACTUATOR
The trip actuator is a small cylindrically shaped
electromagnetic device which acts mechanically to
trip the circuit breaker. In general, it is comprised of
a permanent magnet, a coil and a spring loaded rod
to produce the mechanical tripping, and a lever for
resetting the actuator after tripping occurs. The
electronic trip unit provides a pulse which
counteracts the effect of the permanent magnet,
allowing the spring loaded rod to act mechanically.
The device is reset when the circuit breaker opens.
Summary of Contents for 50 VCP-TR16
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