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POWE R REQU IREMENTS, GENERAL
All alternating-current (A C) operated devices are a f fected by frequency.
sinusoidal wave forms can be analyzed as a fundamental frequency plus harmonics o f
the fundamental frequency, it follows that alternating-current devices (relays) will
be a f fected by the applied wave form.
There fore,
in
order
essential to use a sine wave o f current and/or voltage.
(i.e., its freedom from harmonics) cannot be expressed as a finite number for any
particular relay; however, any relay using tuned circuits, R L or RC networks, or
saturating electromagnets (such as time-overcurrent relays) , would be essentially
a f fected by non-sinusoidal wave forms.
Similarly, relays requiring D C control power should be tested using direct current
(D C)
and not
full-wave recti fied power.
filtered, many relays will not operate properly due to the dips in the recti fied
power.
Zener diodes, for example, can turn o f f during these dips.
rule, the DC source should not contain more than 5% ripple.
TIME OVE RVOLTAGE UNIT
Rotate the time dial slo\'Jly, and check by means o f a lamp that the contacts just
close at the zero ( 0) time-dial setting.
The point at which the contacts just close can be adjusted by running the stationary
contact brush in or out by means o f its adjusting screw.
With the contacts just closing at No. 0 time setting, there should be su f ficient gap
between the· stationary
approximately 1/32 inch wipe.
The minimum voltage at which the contacts will just close is determined by the tap
setting in the tap block at the top o f the support structure.
section.
The pickup o f the time overvoltage unit for any voltage tap setting is adjusted by
means o f a spring-adjustment ring.
\'Jinds
or
unwinds
voltage o f the unit may be brought into agreement with the tap setting employed, i f
this adjustment has been disturbed.
This adjustment also permits obtaining any desired setting intermediate between the
various tap settings.
higher tap be used.
with the time/voltage characteristics of Figures 8 and 9 if the relay has been
adjusted to pick up at a value other than tap value, because the torque level of the
relay has been changed.
Time Setting
The setting o f the time dial d etermines the length o f time the unit requires to
close the contacts when the voltage reaches a predetermined value.
just closed when the time dial is set on zero ( 0) .
the d isk must travel the maximum amount to close the contacts, and there fore this
setting gives the maximum time setting.
to
test
alternating-current
contact
brush
See Figure 1.
the
spiral
control
I f such an adjustment is required, it is recommended that the
It should be noted that the relay will not necessarily agree
GEK-49865
(A C)
Unless the recti fied
and
its metal
The spring-adjustment ring either
spring.
By
turning
When the time dial is set on 10,
11
Since non
relays properly,
The purity o f the sine wave
supply is well
As a general
backing
strip
to
See CHARACTERISTICS
the
ring,
the operating
The contacts are
it
is
ensure
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