20
IZM32 / IN32 low voltage air circuit breaker
MN013017EN May 2022 www.eaton.com
Section 3: Circuit breaker description and operation
Figure 3-9 Installed PXR trip unit
3-4 Electronic tripping system
Series IZM32 / IN32 circuit breakers use a three-part
tripping
system:
• Microprocessor-based trip unit connected to a frame
rating module;
• Rogowski coil type current sensors; and
• Trip actuator.
All three parts of the tripping unit are discussed here in
general. For detailed information pertaining to the different
available trip unit models and other breaker or accessory
information, refer to PXR20/25 instructions manual.
See important frame rating module information on
next page regarding the tripping system.
3-4.1 Microprocessor-based trip unit
Series IZM32 / IN32 circuit breakers utilize the PXR family
of electronic trip units whose main features are summarized
in Table 3.1.
The electronic trip units are self-powered devices. The
protection settings can be set from the front panel. When
the circuit breaker is closed, no external power is required
to operate their protective systems. Current signal levels
and the control power are derived from the current sensors.
All trip units are true RMS current sensing devices.
A functional local test of the trip unit’s primary electronic
circuitry and the circuit breaker’s mechanical tripping action
can be performed through the trip unit’s USB receptacle.
Table 3.1 Series PXR trip units.
Functions
PXR 20
PXR 25
LSIG protection
Yes
Yes
Disable (I)
Yes
Yes
GF protection
Option
Option
GF alarm
Option
Option
Display
Yes
Yes
Programmable
No
No
Current metering
Yes
Yes
Power/energy metering
No
Yes
Power quality metering
No
No
Communication
Yes
Yes
3-4.2 Rating plug
A rating plug is not required with PXR trip units. See frame
rating module information on next page.
3-4.3 Current sensors
Rogowski coil type current sensors are installed on the
load terminals at the bottom rear of the circuit breaker. The
sensors furnish the trip unit with a signal and the energy
required to trip the circuit breaker.
An external neutral current sensor is available for customer
installation, and must be ordered separately.
3-4.4 Frame rating module
The PXR frame rating module is mounted just behind
the trip unit and stores data related to the breaker’s
ratings (including the maximum continuous RMS current),
manufacturing information, and health of the breaker frame.
The interchangeable trip unit attaches to the permanent
frame rating module. Since the PXR trip unit no longer
requires a fixed type rating plug, the continuous current (In)
rating is factory programmed in the frame rating module.
The programmed value of I
n
is shown on the trip unit’s
LCD display and printed on the Battery cover at the lower
right corner of the trip unit. The In rating displayed and
programmed will be equal to or less than the breaker
frame’s maximum rated current as listed on the nameplate.
The breaker’s I
n
rating can be re-programmed by interfacing
with the USB port on the trip unit. Please contact
your Eaton sales representative for details on proper
re-programming of the trip unit.
