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Instruction Booklet
IB48088
Effective July 2021
Instructions for Eaton’s 7.2 kV Ampgard AR
(arc resistant motor control center)
(Compliant to IEEE C37.20.7-2017)
EATON
www.eaton.com
1.5 Product description
The controller consists of a non-load break isolation switch, medium
voltage current-limiting fuses, one or more Type SL vacuum-break
contactors, a set of current transformers, plus control and protection
devices. The isolating switch has a limited make and break rating,
suitable only for closing and opening limited transformer magnetiz-
ing currents. For applications other than those indicated, consult
your Eaton representative.
Each controller occupies all or a portion of a steel structure that may
also enclose a horizontal bus system to distribute power to two
or more structures and a vertical bus system to connect individual
starters to the horizontal bus. The controllers are configured for
full-voltage or reduced-voltage starting, reversing or non-reversing
applications. The controller is available with bolt-in power fuses only.
The contactor of the controller may have bolted connections or
stab-in connections. The contactor is held in place by a set of rails
mounted in the lower part of the cell. The current transformers are
typically mounted immediately after the load-side stabs. The motor
load connections are mounted to the left of the power fuses, facing
forward.
The flow of current through a controller can be described as follows:
The isolation switch line finger assembly (fixed portion) mounted at
the back of the controller rear panel serves to connect to the isola-
tion switch stab (removable portion). When the isolation switch is
closed, the power flows from the isolation switch line finger assem-
bly to the stab and then through the flexible shunt(s) to the upper
fuse mounting. The upper fuse mounting serves the purpose of
placing the power fuses at the back of the rear panel. The top of the
fuse is bolted to the upper fuse mounting behind the service barrier.
The bottom end of the power fuses are connected to the lower fuse
mounting that contain the line-side bolted or stab-in connections for
the main contactor. These connections serve to connect to the line
finger assemblies of the main contactor. With the main contactor
energized, power flows through the contactor’s vacuum interrupters
to the contactor load fingers, which are engaged on to the contactor
load-side stabs. Medium voltage cables connect the contactor load-
side stabs to the motor load connections.
Figure 2. Components.
1.5.1 Isolation switch
The Ampgard AR isolation switch is compartmentalized to prevent
phase-to-phase arcing during a fault event. The switch features are
described in IB48041 (400 A) and IB48043 (800 A) (see
).
1.5.2 Power fuses
Ampgard AR controllers are supplied with Eaton type CLS or HLE
current-limiting power fuses. The controller includes bolt-in, current-
limiting power fuses. All fuses include an indicator that pops up
when the fuse has blown. Optional blown fuse trip bar assembly
can be mounted on the controller isolation switch and is wired to
trip the controller off-line in the event of a blown fuse (see
Figure 3. Optional blown fuse trip bar assembly.
Ampgard AR power fuses are installed behind the service barrier.
The service barrier must be installed during normal operation to
maintain the arc resistant rating of the equipment.
To access the power fuses, follow the below steps:
1. Remove the six bolts shown circled in
and set them
aside for later reassembly.
2. Tilt the service barrier towards you from the top using the two
black handles. The service barrier will tilt towards you about
30 degrees before it is stopped by the phase barriers sticking
through it at the bottom.
3. Lift the service barrier up towards you and at the same time
angling it away from the isolation switch interlock rod.
4. Set it aside safely. The service barrier weighs approximately 20
lbs (9.07 kg).
Blown fuse
Indicator assembly
Isolation
switch
Power fuse
service barrier
Handle
mechanism
Control
terminal
block
Motor load
connection
Contactor
