ABB COV Series Instruction Leaflet

Effective: November 1999
Supersedes I.L. 41-116J, Dated May 1997
|
( ) Denotes Changed Since Previous Issue
This instruction leaflet applies to the
following types of relays:
COV-6 Definite Minimum Time Relay
COV-7 Moderately Inverse Time Relay
COV-8 Inverse Time Relay
COV-9 Very Inverse Time Relay
COV-11 Extremely Inverse Time Relay
!
CAUTION
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely,
inspect the contacts to see that they are clean
and close properly, and operate the relay to
check the settings and electrical connections.
1.0 APPLICATION
The COV relay is applicable where it is desired that
an overcurrent unit be set to operate on less than full
load current when the voltage falls below a predeter-
mined value, and it is desired not to operate for any
magnitude of current when the voltage is above the
predetermined value. A typical application is overcur-
rent back-up protection for generators.
2.0 CONSTRUCTION AND OPERATION
The relay consists of an overcurrent unit, a voltage
unit with adjustable resistor, an indicating contactor
switch unit and an indicating instantaneous trip unit
when required.
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is desired
by purchaser regarding this particular installation, operation or maintenance of this equipment, the local Asea
Brown Boveri representative should be contacted.
Printed in the USA
ABB Automation Inc.
Substation Automation and Protection Division
Coral Springs, FL 33065
Type COV Voltage Controlled
Overcurrent Relay
(50 and 60 Hertz)
2.1
The electromagnets for the types COV-6, COV-7,
COV-8 and COV-9 relays have a main tapped coil
located on the center leg of an "E" type laminated
structure that produces a flux which divides and
returns 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 electromagnet for the COV-11 relay has a main
coil consisting of a tapped primary winding. Two iden-
tical 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
The indicating contactor switch is a small dc operated
clapper type 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 con-
tacts bridge two stationary contacts, completing the
trip circuit. Also during this operation two fingers on
the armature deflect a spring located on the front of
the switch, which allows the operation indicator target
to drop. The target is reset from the outside of the
case by a push rod located at the bottom of the cover.
The front spring, in addition to holding the target, pro-
vides restraint for the armature and thus controls the
pickup value of the switch.
OVERCURRENT UNIT (CO)
INDICATING CONTACTOR SWITCH UNIT
(ICS)
Instruction Leaflet
41-116K