assignment
Question 2
a) Rotary Variable Differential Transformer (RVDT)
Construction of RVDT
RVDT is almost identical in the construction with LVDT. The ferrite core in LVDT is replaced by heart or cardioids shaped core. This rotational movement of the shaft creates the imbalance in the external circuit and this imbalance signal is used to measure the angular displacement of the shaft. RVDT give linear output up to displacement of +-40 degree. Then output starts becoming nonlinear.
Operation of RVDT’s
The two induced voltages of the secondary windings, V1 and V2, vary linearly to the mechanical angle of the rotor, :
where G is the gain or sensitivity. The second voltage can be reverse determines by:
The difference V1 V2 gives a proportional voltage:
and the sum of the voltages is a constant :
This constant gives the LVDT great stability of the angular information, independence of the input voltage or frequency, or temperature, and enables it to also detect a malfunction.
Putting the above mathematical equations in some theoretical form, the working of RVDT can be explained as below:-
• Basic RVDT construction and operation is provided by rotating an iron-core bearing supported within a housed stator assembly. The housing is passivized stainless steel. The stator consists of a primary excitation coil and a pair of secondary output coils. A fixed alternating current excitation is applied to the primary stator coil that is electromagnetically coupled to the secondary coils.
• This coupling is proportional to the angle of the input shaft. The output pair is structured so that one coil is in-phase with the excitation coil, and the second is 180 degrees out-of-phase with the excitation coil. When the rotor is in a position that directs the available flux equally in both the in-phase and out- of- phase coils, the output voltages cancel and result in a zero value signal. This is referred to as the
a) Rotary Variable Differential Transformer (RVDT)
Construction of RVDT
RVDT is almost identical in the construction with LVDT. The ferrite core in LVDT is replaced by heart or cardioids shaped core. This rotational movement of the shaft creates the imbalance in the external circuit and this imbalance signal is used to measure the angular displacement of the shaft. RVDT give linear output up to displacement of +-40 degree. Then output starts becoming nonlinear.
Operation of RVDT’s
The two induced voltages of the secondary windings, V1 and V2, vary linearly to the mechanical angle of the rotor, :
where G is the gain or sensitivity. The second voltage can be reverse determines by:
The difference V1 V2 gives a proportional voltage:
and the sum of the voltages is a constant :
This constant gives the LVDT great stability of the angular information, independence of the input voltage or frequency, or temperature, and enables it to also detect a malfunction.
Putting the above mathematical equations in some theoretical form, the working of RVDT can be explained as below:-
• Basic RVDT construction and operation is provided by rotating an iron-core bearing supported within a housed stator assembly. The housing is passivized stainless steel. The stator consists of a primary excitation coil and a pair of secondary output coils. A fixed alternating current excitation is applied to the primary stator coil that is electromagnetically coupled to the secondary coils.
• This coupling is proportional to the angle of the input shaft. The output pair is structured so that one coil is in-phase with the excitation coil, and the second is 180 degrees out-of-phase with the excitation coil. When the rotor is in a position that directs the available flux equally in both the in-phase and out- of- phase coils, the output voltages cancel and result in a zero value signal. This is referred to as the