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I.L 40-100J
2.
CONSTRUCTION AND OPERATION
The type CO relays consist of an overcurrent unit
(CO), either an Indicating Switch (ICS) or an ac Aux-
iliary Switch (ACS) and an Indicating Instantaneous
Trip unit (IIT) when required.
2.1
Electromagnet
The electromagnets for the types CO-5, CO-6, CO-
7, CO-8 and CO-9 relays have a main tapped coil lo-
cated on the center leg of an "E" type laminated
structure that produces a flux which divides and re-
turns through the outer legs. A shading coil causes
the flux through the left leg to lag the main pole flux.
The out-of-phase fluxes thus produced in the air gap
cause a contact closing torque.
The electromagnets for the types CO-2 and CO-11
relays have a main coil consisting of a tapped prima-
ry winding and a secondary winding. Two identical
coils on the outer legs of the lamination structure are
connected to the main coil secondary in a manner so
that the combination of all the fluxes produced by the
electromagnet result in out-of-phase fluxes in the air
gap. The out-of-phase air gap fluxes produced
cause a contact closing torque.
2.2
Indicating Contactor Switch Unit (ICS)
The dc indicating contactor switch is a small clapper
type device. A magnetic armature, to which-spring
mounted contacts are attached, is attracted to the
magnetic core upon energization of the switch.
When the switch closes, the moving contacts bridge
two stationary contacts, completing the trip circuit.
Also during this operation two fingers on the arma-
ture deflect a spring located on the front of the
switch, which allows the operation indicator target to
drop.
The front spring, in addition to holding the target,
provides restraint for the armature and thus controls
the pickup value of the switch.
2.3
AC Auxiliary Switch (ACS)
The ac auxiliary switch is a small ac operated clap-
per device. A magnetic armature, to which leaf-
spring mounted contacts are attached, is attracted to
the magnetic core upon energization of the switch.
When the switch closes, the moving contacts bridge
two stationary contacts completing the trip circuit. Al-
2
Courtesy of NationalSwitchgear.com
so, during the operation, two fingers on the armature
deflect a spring located on the front of the switch
which allows the operation indicator target to drop.
A core screw accessible from the top of the switch
provides the adjustable pickup range.
2.4
Indicating Instantaneous Trip Unit (IIT)
The instantaneous trip unit is a small ac operated
clapper type device. A magnetic armature, to which
leaf-spring mounted contacts are attached, is at-
tracted to the magnetic core upon energization of the
switch. When the switch closes, the moving contacts
bridge two stationary contacts completing the trip cir-
cuit. Also, during the operation, two fingers on the ar-
mature deflect a spring located on the front of the
switch which allows the operation indicator target to
drop.
A core screw accessible from the top of the switch
and taps on the coil provide the adjustable pickup
range.
3.
CHARACTERISTICS
The relays are generally available in the following
current ranges:
Range
.5 - 2.5
0.5, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5
1 - 12
1.0, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5,
4.0, 5.0, 6.0, 7.0, 8.0, 10.0, 12.0
These relays may have either single or double circuit
closing contacts for tripping either one or two circuit
breakers. The relays are wired per the internal sche-
matics of Figure 1 to 9.
The time vs. current characteristics are shown in Fig-
ures 10 to 16. These characteristics give the contact
closing time for the various time dial settings when
the indicated multiples of tap value current are ap-
plied to the relay.
3.1
Trip Circuit
The main contacts will close 30 amperes at 250 volts
dc and the seal-in contacts of either the indicating
contactor switch or the ac auxiliary switch will carry
this current long enough to trip a circuit breaker.
Taps
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