# MOVING IRON INSTURMENT

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## Presentation Transcript

### CENTURION UNIVERSITY OF TECHNICAL AND MANEGEMENT :

CENTURION UNIVERSITY OF TECHNICAL AND MANEGEMENT Presented by---- Rajeev Ranjan (Electrical and Electronic Engg.) JITM(PARALAKHMUNDI)

### MOVING IRON INSTURMENT :

MOVING IRON INSTURMENT Moving Iron Instruments          M.I instruments are mainly used for the measurement of alternating currents and voltages, though it can also be used for d.c measurements.

### THERE ARE TWO TYPES OF MOVING-IRON INSTRUMENTS:

THERE ARE TWO TYPES OF MOVING-IRON INSTRUMENTS 1)ATTRACTION TYPE 2)REPULSION TYPE

### ATTRACTION TYPE:

ATTRACTION TYPE     In this type of instrument, a single soft iron vane (moving iron) is mounted on the spindle, and is attracted towards the coil when operating current flows through it.

### Deflecting torque equation:

Deflecting torque equation The force F, pulling the soft -iron piece towards the coil is directly proportional to; a) Field strength H, produced by the coil. b)pole strength ‘m’ developed in the iron piece. F α mH Since, m α H, F α H 2 Instantaneous deflecting torque  α H 2 Also, the field strength H = μi If the permeability(μ) of the iron is assumed constant, Then,   H α i Where, i  instantaneous coil current, Ampere Instantaneous deflecting torque α i 2 Average deflecting torque, T d α mean of i 2 over a cycle. Since the instrument is spring controlled,                                              T c α θ In the steady position of deflection, T d = T c                                              θ α mean of i 2 over a cycle                                                 α I 2

### REPULSION TYPE:

REPULSION TYPE In this two soft iron vanes are used; one fixed and attached the stationary coil, while the other is movable (moving iron), and mounted on the spindle of the instrument

### Deflecting torque:-:

Deflecting torque:-    The deflecting torque results due to repulsion between the similarly charged soft- iron pieces or vanes. If the two pieces develop pole strength of m 1 and m 2 respectively, then;                        Instantaneous deflecting torque α m 1 m 2 α H 2 If the permeability of iron is assumed constant, then;  H α i ,  where, i  is the coil current                           Instantaneous deflecting torque α i 2  Average deflecting torque, T d α mean of i 2 over a cycle.   Since the instrument is spring controlled, T c α θ  In the steady position of deflection, T d = T c                                                           θ α mean of i 2 over a cycle.                                                              α  I 2

### MOVING IRON AMMETER:

MOVING IRON AMMETER

### MOVING IRON VOLTMETER:

MOVING IRON VOLTMETER

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