GEH-764AB
Polyphase Switchboard Watthour Meters
recess in the meter base properly. The sealing screws
should not be tightened any more than necessary to
produce a slight compression of the felt gasket in the
recess in the meter base.
CONNECTIONS
The connection diagrams in this book show ap
proved methods of wiring the apparatus. Other
methods are possible which are electrically equivalent
and which for particular installations may result in
more convenient or economical wiring. If properly
{;Onnected in the circuit, the disk will rotate counter
clockwise, viewed from above.
Connections for the DSM and DSW type meters
are identical to those for the DS type meters except
for the register motor connections for the DSM and
the contact device terminal connections for the DSW
line of meters.
The current terminals are identified by the letter
C, the potential terminals by the letter P and the
contact device terminals by the letters K, Y, and
Z.
These three terminals and studs are furnished whether
the meter has 2-wire or 3-wire contact devices. For
2-wire contact devices only K and
Z
are connected,
while for 3-wire contact devices all three are used.
Letters identifying the terminals are stamped on the
base.
It is frequently desirable to use transformers in
circuits of over 150 volts. The cases of meters which
are used with current and potential transformers
should be connected to the grounded side of the sec
ondary circuit of such transformers. For this purpose
No. 12 Awg copper wire is suitable.
At the earth end of the wire the usual precautions
employed in connection with lightning arresters should
be followed.
POLARITY MARKINGS
Instrument transformers have polarity markings of
white paint or markers,
H1
for primary and
X1
for
secondary, on or near one primary and one secondary
terminal. These markings denote the relative polar
ity and facilitate making proper connections for cor
rect direction of rotation of watthour meters. The
relation of the marked leads is such that the instan
taneous direction of the current in them is the same;
namely, toward the transformer in the marked prim
ary lead and from the transformer in the marked
secondary lead, or vice versa. These polarity mark
ings are indicated in the connection diagrams and
should be followed irrespective of their physical lo
cation on the transformers.
POTENTIAL INDICATING LAMPS
Meters are furnished with potential circuit indicat
ing lamps and have special potential coils with an
4
auxiliary winding connected to these lamps as illust
rated in Fig.
14.
METERS FOR USE WITH CURRENT
TRANSFORMERS
In order to utilize effectively the accuracy of these
meters, 2.5-ampere meters are used with instrument
current transformers. The current coils have double
the normal turns of the standard 5-ampere meter. The
torque is therefore double, and affords the advantages
inherent in such high-torque characteristics and with
practically no sacrifice in accuracy throughout the
working range.
Under no conditions should the current circuits of
a transformer-rated meter be opened without first
short-circuiting the secondary winding of the current
transformer. This may be done either at the trans
former terminals or the meter current terminals.
Removal of the connection plug in drawout type
meters automatically short-ciPcuits the current termi
nals so that the meter unit can safely be removed
from the case.
CALIBRATING ADJUSTMENTS
The letters S and F and the arrows on the retarding
magnets denote the proper direction to turn all adjust
ing screws for calibrating the meter.
Full
Load
Full-load adjustment is accomplished by movable
permanent magnets.
The two magnets in the two-stator meter and the
three magnets of the three-stator meter may be placed
in an approximately correct position and clamped.
A change in the position of any magnet affects all
stators alike. Moving the magnet in will increase the
speed of the meter, while conversely, moving the
magnet out will decrease the speed of the meter.
When the proper adjustment has been obtained, the
magnet should be clamped securely to its support by
means of the clamping screw.
To facilitate the clamping of the magnets, hexagon
al head screws are provided which are easily turned
with a wrench.
Do not use special open-end wrenches
for this purpose. They are not strong enough.
Light Load
The brackets supporting the lag and light load
plates are attached to the frame. The one for the
upper stator is located just under the disk and the
one for the lower stator, and the middle and lower in
three-stator meters, is just over the disk.
The light-load adjustment is- made by turning the
adjusting screw located at the extreme right of the
bracket.
Turning the screw counterclockwise in
creases the speed of the meter and clockwise decreases
it. The screw at the extreme left of the bracket should
not be disturbed.
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