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  HLD03/DD58 Electromechanical Single-Phase Meter
 Construction
Meter
Base
The meter base, made of bakelite, is highly resistant to creep
currents. It is integrated with the meter terminal block. A special
terminal can be used to separate the current and voltage circuits for
the calibration and testing of the meter.
Terminal Cover
The terminal cover is made of acrylonitrile-butadiene-styrene (ABS),
bakelite, polycarbonate or sheet steel, depending upon the consumer's
request. It can be short or extended.
A connection diagram is impressed into the terminal cover from the
inside.
Frame and Magnetic Brake Assembly
The frame is die-cast from an aluminum alloy. It is robust and light.
The driving elements are mounted on this rigid piece with two screws.
Light adjustment is fixed to the frame.
Two magnets manufactured from AlNiCo alloy, a substance providing a
particularly strong coercive force, form the magnetic brake. These
magnets are very resistant to the demagnetization provoked by any high
short-circuit current.
Plates made of a special alloy provide large temperature compensation.
Driving Element
The voltage electromagnet is made of a laminated silicon-steel core
used for mounting the voltage coils and the temperature compensating
set.
The current electromagnet is made of a laminated silicon-steel core
used for mounting the current coils, the power factor adjustment and
the overload compensating set.
Meter Rotor
One hundred (100) equally spaced marks are printed around the
circumference of the rotor disk to allow stroboscopic calibration and testing.
The black marks for observing meter rotation are easily visible on the
top surface of the disk.
Bearing
The upper bearing consists of a steel pin. The pin is pressed in to the
brass sleeve attached to the disk shaft.
There are two types
of the lower bearing.
The double-jewel bearing consists of a steel ball running freely in
between two synthetic corundum jewels. One of the two jewels is fixed
and the other rotates with the shaft. The double-jewel bearing also has
a spring support for automatic readjustments and protection against any
damage due to shock and vibration.
The magnetic
suspension bearing consists of two ring shaped homopolar-repelling
magnets made of AlNiCo alloy with high coercive force and retentivity.
The entire assembly is guided with a steel pin moving in a graphite
sleeve offering minimum friction.
Register
The standard cyclometer type meter has six drums mounted on a support
of stamped aluminum. The small movable shaft rotates over
self-lubricating plastic bearings.
Unidirectional register is available and reverse running stop can be
incorporated.
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