ABB COV-9 Памятка по эксплуатации - Страница 2

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41-116.1C

duced 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

VOLTAGE UNIT (V)

The voltage unit is an induction type cylinder type

unit.

Mechanically, the voltage unit is composed of four

basic components: A die-cast aluminum frame, an

electromagnet, a moving element assembly, and a

molded bridge.

The frame serves as the mounting structure for the

electromagnet and for a magnetic core. The mag-

netic core houses the lower pin bearing and is

secured to the frame by a locking nut. The bearing

can be replaced if necessary, without having to

remove the magnetic core from the frame.

The electromagnet has two pairs of voltage coils.

Each pair of diametrically opposed coils is connected

in series. In addition, one pair is in series with an

adjustable resistor. These sets are paralleled as

shown in Figure 2, page 11. The adjustable resistor

serves not only to shift the phase angle of the one

flux with respect to the other to produce torque, but it

also provides a dropout adjustment.

Locating pins in the electromagnet are used to accu-

rately position the lower pin bearing, which is

mounted on the frame, with respect to the upper pin

bearing, which is threaded into the bridge. The elec-

tromagnet is secured to the frame by four mounting

screws.

The moving element assembly consists of a spiral

spring, contact carrying member, and an aluminum

cylinder assembled to a molded hub which holds the

shaft. The shaft has removable top and bottom jewel

bearings. The shaft rides between the bottom pin

bearing and the upper pin bearing with the cylinder

rotating in an air gap formed by the electromagnet

and the magnetic core. The stops for the moving ele-

ment contact arm are an integral part of the bridge.

The bridge is secured to the electromagnet and

frame by two mounting screws. In addition to holding

the upper pin bearing, the bridge is used for mount-

ing the adjustable stationary contact housing. The

stationary contact housing is held in position by a

spring type clamp. The spring adjuster is located on

the underside of the bridge and is attached to the

moving contact arm by a spiral spring. The spring

adjuster is also held in place by a spring type clamp.

With the contacts closed, the electrical connection is

COV Voltage Controlled Overcurrent Relay

made through the stationary contact housing clamp,

to the moving contact, through the spiral spring out to

the spring adjuster clamp.

2.3

INDICATING CONTACTOR SWITCH UNIT

(ICS)

The indicating contactor switch is a small dc oper-

ated 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.

3.0 CHARACTERISTICS

To prevent the relay from operating for currents

above the overcurrent unit pickup, the voltage unit

contact is connected to control the telephone relay

whose contacts are connected in the shading coil cir-

cuit of the overcurrent unit. The voltage contact is

held open at voltage above the set point, to prevent

torque from being produced in the overcurrent unit.

This arrangement yields a tripping characteristic as

shown in Figure 3, page 12.

3.1

OVERCURRENT UNIT

The relays are generally available in the following

overcurrent unit ranges:

RANGE

0.5 - 2.5

0.5

0.6

2 - 6

2.5

4 - 12

These relays may have either single or double circuit

contacts for tripping either one or two circuit break-

ers.

The time vs. current characteristics are shown in Fig-

ures 4 to 8, starting on page 13. These characteris-

tics give the contact closing time for the various time

dial settings when the indicated multiples of tap value

current are applied to the relay

3.2

VOLTAGE UNIT

The contacts can be adjusted to close and energize

TAPS

0.8

1.0

1.5

2.0

2.5

3.5