Safety Isolation System
ElectroGuard
Overview
Principle of Operation
Power Circuit
1IC
Incoming
3 Phase
Power
H1
X1
Disconnecting
Means/Branch
Circuit Protection
➊
H2
Trans.
X2
GC
Voltage
Decay
Relays
(VDR)
2IC
To Motor
Controllers
To Loads
After using the normal stopping
method of the machine or process,
the machine operator turns a
Remote Lockout Station handle
from the “On” to “Off ” position.
The station signals the isolation
contactors (1IC and 2IC) to drop
out and isolate the supply voltage
from the loads (see Control
Circuit).
When system residual voltage
decays to pre-determined levels,
the grounding contactor (GC) is
energized, connecting the load to
ground (see Power Circuit). The
grounding contactor (GC) is
electrically and mechanically
interlocked with the isolation
contactors (1IC and 2IC).
The “System Isolated” Light will
now illuminate on the Remote
Lockout Station to indicate the
system is isolated. The machine
operator then Locks-Out and
Tags-Out the station in the “Off ”
position.
Control Power
Grd
Control Circuit
Remote Lockout Station
Off
On
GC
1IC
GC
2IC
VDR
1IC
2IC
GC
Mechanically
Interlocked
1IC, 2IC,
&
GC are
mechanically
and electrically
interlocked
GC
1IC
2IC
System Isolated (*)
(*) = “On” when the Remote
Lockout Station switch is “Off”
➊
Available factory installed within the ElectroGuard as an option.
Optional Features
• Four (4) or ten (10) port Expansion Modules to permit additional Remote
Lockout Stations to be used (see page 12-16 for details).
• Pneumatic Isolation Module to isolate pneumatic energy (see page 12-15 for
details).
• Status communication to a remote PLC (see page 12-17 for details).
• Fusible disconnect switch (Bulletin 2032) or thermal-magnetic circuit breaker
(Bulletin 2033) to provide branch circuit protection.
Optional Pneumatic Isolation Module
12-3
ALLEN-BRADLEY [ Allen-Bradley ]
