ABB COV-6 Памятка по эксплуатации - Страница 6

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41-116.1C

tionary contacts should be approximately

1/64".

2) For relays identified with a " T ", located at

lower left of stationary contact block, the

index mark on the movement frame will coin-

cide with the "0" mark on the time dial when

the stationary contact has moved through

approximately one-half of its normal deflec-

tion. Therefore, with the stationary contact

resting against the backstop, the index mark

is offset to the right of the "0" mark by

approximately .020". The placement of the

various time dial positions in line with the

index mark will give operating times as shown

on the respective time-current curves. For

double trip relays, the follow on the stationary

contacts should be approximately 1/32".

3) Set the time dial in position 6.

B. Minimum Trip Current

The adjustment of the spring tension in setting

the minimum trip current value of the relay is

most conveniently made with the damping

magnet removed.

With the time dial set on "O", wind up the spiral

spring by means of the spring adjuster until

approximately 6-3/4 convolutions show.

The spiral spring can be adjusted with the

spring shield in place as follows. One slot of

the spring adjuster will be available for a screw-

driver in one window of the front barrier of the

spring shield. By adjusting this slot until a bar-

rier of the spring shield prevents further adjust-

ment, a second slot of the spring adjustment

will appear in the window on the other side of

the spring shield barrier. Adjusting the second

slot in a similar manner will reveal a third slot in

the opposite window of the spring shield.

Adjust the control spring tension so that the

moving contact will leave the backstop at tap

value current + 1.0% and will return to the

backstop at tap value current - 1.0%.

C. Time Curve Calibration – Install the perma-

nent magnet.

Apply the indicated current per Table 1 for the

permanent magnet adjustment (e.g., COV8, 2

times tap value) and measure the operating

time. Adjust the permanent magnet keeper

until the operation time corresponds to the

value of Table 1.

COV Voltage Controlled Overcurrent Relay

For type COV-11 relay only, the 1.30 times tap

value operating time from the number 6 time

dial position is 54.9 ± 5% seconds. It is impor-

tant that the 1.30 times tap value current be

maintained accurately. The maintaining of this

current accurately is necessary because of the

steepness of the slope of the time-current

characteristic (Figure 8, page 17). A 1% varia-

tion in the 1.30 times tap value current (includ-

ing

measuring

change the nominal operating time by approxi-

mately 4%. If the operating time at 1.3 times

tap value is not within these limits, a minor

adjustment of the control spring will give the

correct operating time without any undue effect

on the minimum pick-up of the relay. This

check is to be made after the 2 times tap value

adjustment has been completed.

Apply the indicated current per Table 1 for the

electromagnet plug adjustment (e.g. COV-8, 20

times tap value) and measure the operating

time. Adjust the proper plug until the operating

time corresponds to the value in Table 1. (With-

drawing

the

left-hand

increases the operating time and withdrawing

the right-hand plug, front view, decreases the

time.) In adjusting the plugs, one plug should

be screwed in completely and the other plug

run in or out until the proper operating time has

been obtained.

Recheck the permanent magnet adjustment. If

the operating time for this calibration point has

changed, re-adjust the permanent magnet and

then recheck the electromagnet plug adjust-

ment.

8.2

VOLTAGE UNIT (V)

A. The upper pin bearing should be screwed

down until there is approximately. 0.25" clear-

ance between it and the top of shaft bearing.

The upper pin bearing should then be securely

locked into position with the lock nut. The lower

bearing position is fixed and cannot be

adjusted.

B. The contact gap adjustment for the directional

unit is made as follows:

With the moving contact in the normally-closed

position i.e., against the left stop on bridge,

screw in the stationary contact until both con-

tacts just close as indicated by a neon lamp in

the contact circuit. Then, screw the stationary

contact in toward the moving contact an addi-

instrument

deviation)

plug,

front

view,

will