18
Trip Units — MicroVersaTrip Plus™
Operation Of MicroVersaTrip Plus™ Trip Units
MicroVersaTrip Plus trip units have a menu of standard and
optional functions. The block diagram shows a fully config-
ured MicroVersaTrip Plus trip unit with ground-fault protec-
tion. The current sensors are special current transformers
that provide the trip unit with its operating power.
Interchangeable rating plugs act as scalars for the outputs of
the current sensors, as well as establish the current rating of
individual breakers. When a four-wire system is used and
ground-fault protection is called for, an external neutral
sensor is necessary.
Block diagram of MicroVersaTrip Plus trip unit
Analog current signals are converted to digital values, and
are measured and compared with established trip settings in
the micro processor’s memory. Any overcurrent or ground
fault condition that exceeds preset conditions produces a
trip signal from the micro processor to the trip actuator.
The trip actuator is a low-energy, positive-action tripping
device. The low-level trip signal counteracts the strength of
the actuator’s permanent magnet, and allows a spring to
unseal the magnet and trip the breaker.
All trip unit protective functions will operate the bell alarm
accessory (if so equipped). The two normally open and two
normally closed contacts will change state whenever the trip
actuator causes the breaker to open. The bell alarm is not
activated by any other manual or electrical tripping means.
Standard And Optional Protective Functions
Standard and optional protective functions for
MicroVersaTrip Plus trip units are shown below. The break-
er settings are programmed in multiples of “In” (rating plug
amp values),”CT”(current sensor amp rating values), and
“LT” (the long-time setting in amps-multiply long-time set-
ting by rating plug amp rating).
Standard
• 3-phase Ammeter with ±2% accuracy.
• Adjustable Long-Time (L) pickup, 0.5- 1.1In, with four
delay bands.
• Adjustable instantaneous (I) pickup, 1.5 - 9/10/13 or
15In.
• Overload and Short Circuit local trip indicators with over-
load pickup warning.
• Test set initiated trip indication.
Options
• Adjustable Short-Time (S) pickup, 1.0 - 9.0LT, and delay
(3 bands) with I
2
t IN/OUT selection.
• Adjustable Ground Fault (G) pickup, 0.2 - 0.6CT, and
delay (3 bands) with I
2
t IN/OUT selection and trip indi-
cator.
• Zone selective interlocking for Ground Fault or Ground
Fault and Short-Time.
• Defeatable Ground Fault function (non-UL).
• Switchable Short Time or Instantaneous and Ground
Fault function (non-UL).
Auxiliary Contact
(Microswitch)
MicroVersaTrip Plus
Trip Unit
24Vdc Power Supply
A/D Converter
(Optional)
Input/Output
A B C N
Phases
(Optional)
A B C N
Phases
Breaker Mounted
Current Sensors
Zone Selective Interlock
Optional Neutral Current
Trip Unit Keypad
Phase
Currents
Rating
Plug
Crystal
Display
with or w/o
Bell Alarm
T
rip Logic
Fault
Fault
Liquid
Lockout
T
rip Actuator
