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On the under- and overvoltage relays such as
the
IAV53A,
IAV53B,
operating voltage for a given tap setting is the mini
mum voltage at which the left-hand contacts close.
The right-hand contacts will then close at a certain
percentage of operating voltage.
change this percentage, the right-hand moving contact
may be rotated on the shaft after first loosening the
clamping screws that hold it in place. Changing the
position of this contact gives an adjustment of this
contact gives an adjustment of the voltage to close
the right-hand contacts between 50 and 95 percent
of the voltage which closes the left-hand contacts.
Changing the position of the right-hand contacts
changes the voltage at which the left-hand contacts
close.
Hence, simultaneous adjustmentes for clos
ing left and right contacts must be made to obtain a
desired characteristic.
TIME SETTING
The time of operation of the overvoltage relays
is determined primarily by the setting of the time
dial, while that for the under- and overvoltage relays
is determined by the spread of the contacts as ex
plained under "Voltage Setting." Further adjustment
is obtained by moving the permanent magnet along
its supporting shelf; moving the magnet in toward
the back of the relay decreases the time while mov
ing it out increases the time.
Fig. 1 shows the time-voltage characteristics of
the Type IA V51A and IAV52A relays with the dial
Before the relay is put in service, it should be
given a partial check to determine that factory ad
justments have not been disturbed. On relays which
have time dials, the dials will be set at zero before
the relay leaves the factory.
change this setting in order to open the relay con
tacts.
The pick-up voltage should be checked on one
or more taps on relays which close contacts on in
creasing voltage.
The drop-out voltage should be
checked on one or more taps on relays which close
contacts on decreasing voltage.
The time-voltage curves should be checked for
one or more settings.
Recommended test connections for the above
test are shown in Fig. 18 for the overvoltage relays
These relays are adjusted at the factory and it
is advisable not to disturb the adjustments.
any reasons, they have been disturbed, the following
points should be observed in restoring them:
IAV53C, and IAV53D, the
If
it is desired to
OPERATION
It is necessary to
MAINTENANCE
If
for
Voltage Relays Type IAV
setting for obtaining each characteristic. To make
time settings, set the time dial to the number re
quired (to give the desired characteristic) by turning
it until the number lines up with the notch in the ad
jacent frame.
The time indicated by the curves is
the time required to close the relay contacts when
the voltage is suddenly increased from a value below
pickup to the value on the curve.
Fig. 2 shows the characteristics of the Type
IA V53A and IA V53 B relay. The time characteristic
of the relay automatically determined by the setting
of the ratio of the voltage to close the right contacts
to the voltage to close the left contacts. Fig. 4 shows
the time-voltage characteristics of the TypeiAV53D
relay. No curve is given for the Type IA V53C since
its time-voltage characteristics are explained under
the
section heading
"Operating Characteristics."
The time-voltage characteristics are plotted in
percent thus
making them applicable for all tap
settings.
INSPECTION
At the time of installation, the relay should be
inspected for tarnished contacts, loose screws, or
other imperfections.
should be corrected in the manner described under
"Maintenance."
such as the
Types IAV51A, IAV51D and IAV52A.
The
under- and overvoltage relays such as the
Types IA V53A,
IA V53B,
be checked for time of closing left contacts by using
connections. shown in Fig. 18, and for closing right
contacts by the connections shown in Fig. 19.
course the seal-in unit shown in the figure is not
used in the case of the IAV53B and IAV53D, but all
stud numbers are correct.
should be substituted for stud numbers 9 and 10 on
Fig. 19 for testing the undervoltage contacts of the
Type IAV53C relay. (See internal diagram, Fig.15).
The relay may be tested while mounted on the
panel, either from its own or another source of
power, by inserting a separate testing plug in place
of the connecting plug. Or, the cradle can be drawn
out and replaced by another which has been laboratory
tested.
DISK AND BEARINGS
The lower jewel may be tested for cracks by
exploring its surface with the point of a fine needle.
GEH-1814
If
any trouble is found, it
IAV53C and IAV53D can
Stud numbers 1 and 2
Of
11
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