GEH-1791
The IJS is not adaptable to applications involving continuous loading of the contact
circuit, since contact welding may result even with contact loadings that are low in
re
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at ion to the interrupting capacity of the contacts.
The contra
1
shou
1
d be
designed to energize the IJS coils when synchronism is to be checked, and to permit
the IJS contacts to be the last to complete a closing circuit that is promptly
bypassed or interrupted.
Cross feed from the energized side to the de-energized side is very low, because the
operating principle of the relay requires the two windings on the operating magnet
to be additive while those on the restraining magnet are subtractive, and,
therefore, the coupling from the bus side to the line side coil on the operating
magnet is practically cancelled by the reverse polarity of the corresponding
coupling between the coils on the restraining magnet.
OPERATING CHARACTERISTICS
The operating coils, mounted on the left-hand side, produce a torque tending to
close the relay contacts.
This torque is proportional to the vector sum of the
voltages whose phase positions are being compared.
The torque produced the
restraint coils is proportional to the vector difference of the voltages.
The
operating torque is maximum when the systems are in synchronism and is 0 when they
are in phase opposition; the reverse is true of the restraining torque.
The closing angle of the relay is defined as the maximum phase displacement of the
two voltages at which the relay wi
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close its contacts when the voltages are at
rated value. The 200 closing angle is considered standard; however, other settings
may be made, as indicated by the voltage-phase-angle characteristics shown in Figure
1.
The time-delay characteristics of the Type IJS relay are obtained primariy by the
time-dial setting.
The time dial controls the distance the contacts must travel
before closure and, hence, controls the time delay.
At No. 10 time-dial setting the
travel is maximum, whereas at No. 0 the contacts are just closed.
A certain amount
of adjustment may be made by changing the position of the drag magnet on its shelf.
Moving it toward the disk shaft decreases the time delay, while moving it away from
the disk shaft increases the time delay.
Typical time vs. phase-angle curves are shown in Figures 5 and 6 for 60-cycle relays
and in Figure 7 for 25-cycle relays.
The model 12IJS51A1 relay has the standard
closing angle setting of 200 and has its drag magnet adjusted to provide 20 seconds
time delay from No. 10 time-dial setting for voltages in phase.
The closing angle
on this relay can be adjusted to angles greater than 200, but with a corresponding
decrease in the time delay, as shown in Figure 5.
The approximate reset time of the 12IJS51A1A relay with both coils de-energized is
100 seconds at the #10 TDS.
The approximate reset time with one coi
1
circuit
energized varies from 3 seconds on the 100 setting to 6 seconds on the 600 setting
at the No. 10 time-dial setting.
The Model 12IJS51A3 and 12IJS52A7A relays, which are designed for use where the
closing angle greater than 200 is required, provides 20 seconds delay at the 400
closing-angle setting, as shown in Figure 6.
It may be adjusted to other closing
angles between 200 and 600 with corresponding changes in time delay, as shown in
Figure 6.
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