GEI-50261
triangle as shown in Figure 9 (b).
In this illustration Vg represents the voltage
unbalance of the line voltages.
The Vg voltage in this case will be equal to
/3
VN
and therefore at pickup:
For example, if we wish the relay to pick up when the unbalance represented by Vg is
20
volts, then we set the relay to pick up when a single-phase voltage of
20
volts
is applied, shown in Figure
10.
2
Consider an unbalance voltage similar to VT
illustration, VT is the voltage shift in each
condition. Here VT is equal to VN, and at pickup:
shown 1n Figure 9 (c) .
In this
of two corners from the balanced
Therefore, if we wish the relay to pick up when the unbalance represented by VT is
10
volts, then the relay should be set to pick up when
V
=
/3
(10)
=
17
.
3
volts.
CONSTRUCTION
The relay components are mounted in a cradle assembly that is latched into a drawout
case when the relay is in operation, but it can be easily removed when desired.
To
do this, the relay is first disconnected by removing the connection plug that
completes the electrical connections between the case block and the cradle block.
To test the relay in its case, this connection block can be replaced by a test plug.
The cover, which is attached to the front of the relay case, contains an interlock
arm that prevents the cover from being put back in place until the connection plugs
have been inserted.
The relay case is suitable for either semi-flush or surface mounting on, all panels
up to
2
inches thick, and appropriate hardware is available.
However, panel
thickness must be indicated on the relay order to ensure that proper hardware will
be included. For outline and drilling dimensions, see Figure
14.
Every circuit in the drawout case has an auxiliary brush, as shown in Figure
11,
to
provide adequate overlap when the connecting plug is withdrawn or inserted.
By
providing this overlap, the auxiliary brushes relieve the main brushes from any
arcing damage.
Also, on circuits that are equipped with shorting bars (see Figure
8),
it is especially important that the auxiliary brush make positive contact as
indicated in Figure
11,
to prevent the opening of important interlock circuits.
RECEIVING, HANDLING
AND
STORAGE
These relays, when not included as part of a control panel, will be shipped in
cartons designed to protect them against damage.
Immediately upon receipt of a
relay, examine it for any damage sustained in transit.
If 1n]ury or damage
resulting from rough handling is evident, file a damage claim at once with the
transportation company and promptly notify the nearest General Electric Sales
Office.
7
www
. ElectricalPartManuals
. com
