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What is the function of the pressure spring in a three-phase energy meter?
It provides mechanical support.
It provides deflection torque to the moving member.
It maintains a constant pressure between the aluminium discs and the disc spindles.
It moves the aluminium discs in response to the torque generated by the magnetic field.
It maintains a constant pressure between the aluminium discs and the disc spindles.
The pressure spring (often referred to as the pivot or bearing tensioning spring) in an induction-type energy meter is designed to maintain consistent axial contact between the rotating aluminium disc assembly and the pivot-bearing structure. This constant pressure ensures minimal vertical play, reduces mechanical friction, and prevents chatter in the moving system during operation.
IS 13779:1999
The pressure spring (often referred to as the pivot or bearing tensioning spring) in an induction-type energy meter is designed to maintain consistent axial contact between the rotating aluminium disc assembly and the pivot-bearing structure. This constant pressure ensures minimal vertical play, reduces mechanical friction, and prevents chatter in the moving system during operation.
TdтАЛ=K1тАЛтЛЕ╬жsтАЛтЛЕ╬жpтАЛтЛЕsin╬Ф
In an energy meter, the moving system consists of an aluminium disc mounted on a spindle. To achieve high sensitivity and accuracy, the spindle is supported by a jewel bearing. The pressure spring exerts a controlled downward force to keep the spindle seated correctly within the bearing, compensating for any vibrations or thermal expansion that could otherwise lead to erratic measurement or mechanical wear.
Reduces the effect of vibration on the meter reading.
Ensures the disc rotates in a strictly horizontal plane.
Maintains longevity of the jewel bearing by preventing excessive 'bouncing' of the spindle.
Crucial for maintaining the calibration accuracy over long durations.
Improved rotational stability of the disc.
Reduced mechanical noise and oscillation during high-load conditions.
Adds a slight frictional component that must be compensated for by the shading bands.
Requires periodic lubrication in some legacy models.
Electromechanical Induction Type Energy Meters.
Analog Watt-hour meters used in legacy electrical distribution networks.
The torque equation for an induction meter is TdтАЛтИЭ╬жpтАЛтЛЕ╬жsтАЛтЛЕsin╬Ф, where ╬жpтАЛ is the pressure coil flux and ╬жsтАЛ is the series coil flux.
Option B is incorrect as deflection torque is produced by the interaction of the electromagnetic fluxes, not the spring.
Option D is incorrect as the magnetic field (not the spring) provides the driving torque.
C is correct тАФ It maintains a constant pressure between the aluminium discs and the disc spindles.
Always remember that in electrical measuring instruments, springs (like control springs) provide restoring torque, whereas in energy meters, specific pressure springs focus on mechanical alignment rather than torque generation.
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