Application - GE IAV51A Instructions Manual

These relays are of the induction disk construc­
tion. The disk is actuated by a potential operating
coil on a laminated U-magnet.
carries the moving contact, which completes the trip
or alarm circuit when it touches the stationary con­
tact or contacts. The disk shaft is restrained by a
spiral spring to give the proper contact closing
voltage, and its motion is retarded by permenanet
magnets acting on the disk to give the correct time
delay.
There is a seal-in unit mounted to the left of
the shaft as shown in Fig. 16.
in
coil series and its contacts in parallel with the
main contacts such that when the main contacts close,
the seal-in unit picks up and seals in.
seal-in unit picks up, it raises a target into view
which latches up and remains exposed until released
button
beneath
by pressing
a
o1 the cover.
The case is suitable for either surface or semi­
flush panel mounting and an assortment of hardware
is provided for either mounting. The cover attaches
to the case and also carries the reset mechanism
when one is required.
have provision for a sealing wire.
The case has studs or screw connections at both
ends or at the bottom only for the external con­
nections. The electrical connections between the
relay units and the case studs are made through
spring backed contact fingers mounted in stationary
molded inner and outer blocks between which nests
a removable connecting plug which completes the
circuits. The outer blocks, attached to the case,
have the studs for the external connections, and the
inner blocks have the terminals for the internal
connections.
The relay mechanism is mounted in a steel
framework called the cradle and is a complete unit
with all leads being terminated at the inner block.
This cradle is held firmly in the case with a latch
at the top and the bottom and by a guide pin at the
back of the case. The cases and cradles are so
constructed that the relay cannot be inserted in the
case upside down. The connecting plug, besides
making the electrical connections between the re­
spective blocks of the cradle and case, also locks
the latch in place. The cover, which is fastened to
the case by thumbscrews holds the connecting plug
in place.
These instructions do not purport to cover all details or variations in equipment nor to provicle lor every possible
contingency to be met in connection with installation,
or should porticuivr problems arise which are not covered sufficiently lor the purche1ser's purposes, the maHer should
be referred to the General Electric Company.
VOLTAGE RELAYS
TYPE IAV
INTRODUCTION
The disk shaft
This unit has its
When the
the lower-left corner
Two of the cover screws
operat
To draw. out the cradle from a single ended
case, the cover must first be removed.
connecting plug can be drawn out.
the trip circuit is first opened, then the voltage
circuits are opened.
has been removed, the lower latch can be released
and the cradle easily drawn out.
cradle, the reverse

APPLICATION

These relays are protective devices to close
trip or alarm circuits whenever the voltage applied
to their operating coils reaches some predetermined
value. Figures 5 through
the applications. The functions are described in
in
greater detail the paragraphs the follow.
OPERATIWG C HARACTERISTICS
The Type IAV51A is an overvoltage relay with
single-circuit closing contacts which close when
the voltage increases to pick-up value as set on the
tap block. The time delay in closing the contacts
is determined by the setting of the time dial at the
top of the shaft. The time-voltage characteristics
of this relay are shown in Fig. 1.
The Type IAV51D
voltage relay normally used for ground fault pro­
tection on a-c rotating machines. It is of the same
general construction as the Type IAV51A relay ex­
cept that it has a capacitor and tapped resisto1·
connected in series with the operating coil.
capacitor is added to tune the circuit, giving a low
pick-up voltage at rated frequency. At rated voltage
the operating U-magnet is highly saturated, in­
creasing the impedance of the circuit thus limiting
the current to a safe value.
sistor are connected to the tap block to provide
a four-to-one range of pickup.
typical external connection diagram, Fig. 6, this
relay is connected to the machine neutral potential
transformer through a closed contact on the auxi­
liary tripping relay, hence is energized only when
a ground occurs. To obtain still lower pickup than
the normal calibration, it is permissible to insert
an inverted potential transformer between the ma­
chine neutral transformer and the relay coil cir­
cuit. Time curves are shown in Fig. 3.
ion or mailttenance. Should further information be delired
Then the
In so doing,
After the connecting plug
To replace the
order should be followed.
8
demonstrate some of
relay is a low pick-up,
The taps on the re­
As shown in the
The
3