Electromechanical Energy Conversion Lab report

Electromechanical Automation Lab 1: EM Energy Conservation Conservation Nicolas Giovanangeli, 11378344 – 11378344 – Lab  Lab Group B

Nicolas Giovanangeli (11378344)

Table of Contents Aim.......................................................................................................................................... 2 Abstract ................................................................................................................................... 2 Materials ................................................................................................................................. 3 Pre Lab..................................................................................................................................... 4 Results/Measurements .......................................................................................................... 10 Discussion .............................................................................................................................. 12 Conclusion ............................................................................................................................. 13 References ............................................................................................................................. 13

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Nicolas Giovanangeli (11378344)

 Aim   

To measure the magnetic flux and torque in a singly excited electromagnetic system. To calculate the flux and torque and compare with measurement. To be familiar with Op-Amp circuits and to use it in a fluxmeter.

 Abstract A 2-pole variable reluctance rotating machine is used as a singly excited electromagnetic system. Calculations of flux variations with rotor angle, based on the machine dimensions and excitation, are used to study the variation in stored energy and hence the machine torque. Flux and torque measurements are performed and the calculated performance is compared with measured performance. The variation of the coil self-inductance with rotor position is also noted. In general an electromechanical system has an electrical part, a mechanical part and a control part. The electrical part may be electrostatic or electromagnetic; the latter will be considered here. In general, an electromagnetic device will have several coils, an electromagnetic circuit with a moving part, and/or permanent magnets. To form an electrical model we need: The resistance of each coil (at the operating temperature) The self inductance or self flux linkage of each coil and its variation with position of the moving part and with the coil current The mutual inductance or mutual flux linkage between all coils and the variation with moving part position and coil currents The induced voltage in each coil due to motion of the permanent magnets relative to the coils  

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To simplify the example, we consider a system with one excited winding (formed of two coils in series) on a 2-pole solid iron stator, and a moving 2-pole solid iron rotor. This is a singly excited variable reluctance machine. (There are coils on the rotor, but these are not used in this experiment.)

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Nicolas Giovanangeli (11378344)

Materials 

       

Lybotec 2-pole rotating machine. The machine has 2-pole salient pole stator with a rated coil current of 2 A, and 2-pole salient pole rotor, shown below. The rotor coils are not used in this lab.

Shaft locker Shaft encoder Shaft encoder counter Commutator-mounted torque arm Salter 10N spring balance Fluxmeter (electronic integrator) Reversing switch Connecting leads with retractable shrouds on the plugs

Note: The spring balance for force measurement may be calibrated in gram weight. (1 g wt = 9.8 × 10-3 newton). Torque = force × radius, its SI unit is newton-metre, Nm.

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Nicolas Giovanangeli (11378344)

Pre Lab

i.

Use the BH curves, shown above, to determine the maximum permeability of cast iron forming the magnetic path.

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Nicolas Giovanangeli (11378344)

ii.

Assuming no fringing and that the iron parts have the permeability calculated above, sketch the magnetic equivalent circuit and derive ideal expressions for the flux linking the stator winding for the rotor angles of to , where is the angle of the rotor when aligned with the stator poles. The dimensions of the ma chine are given in below.

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Nicolas Giovanangeli (11378344)

iii. Plot the flux variation with rotor angle over to range for current I=1.5A DC (75% of its rated value).

Magnetic Flux (φ) vs Rotor Angle (θ) 0 1 2 3 4

    )       φ     (    x    u     l    F    c    i    t    e    n    g    a    M

5 6 7 8 9 10 11 12 13

Rotor Angle (θ)

iv. From the analytic expression calculated in (ii) for the flux, derive an expression for the o

o

derivative of the flux with respect to rotor angle over 0  to 76 .

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Nicolas Giovanangeli (11378344)

v.

From the flux derivative, determine and plot the restoring torque for I=1.5A DC, over the o

o

range of rotor angles from -76  to +76 . Note that , the restoring torque will take a negative value and vice versa.

Torque (T) vs Phase Angle ( θ)

-76 -75 -74 -73 -72

    )    T     (    e    u    q    r    o    T

-71 -70 -69 -68 -67 -66

Phase Angle (θ)

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-65

Nicolas Giovanangeli (11378344)

vi. On a graph paper, sketch flux and torque variation with rotor position over a range, making sensible assumptions as to machine symmetry. Flux vs Torque, 0°