Q2 (a) A separately excited DC machine is used to drive a conveyor belt. The arm

Question

Q2 (a) A separately excited DC machine is used to drive a conveyor belt. The armature has the electrical parameters Va=120V, Ra=2?, La=10mH, the field current If=10A and the mutual inductance Lad=80mH.

(i) Sketch the equivalent circuit and derive the electrical equation describing the armature circuit.

(ii) Derive the steady-state voltage and torque equations.

(iii) Use your equations from part (ii) to derive an equation linking torque and speed.

(iv) Sketch the torque-speed profile of this machine on a graph. You are not required to use graph paper, but your sketch should be accurately and carefully drawn.

(b) An electrical machine is connected to a mechanical load. The system has the following mechanical parameters: Electrical torque developed

Te = 48-0.32? Nm

Machine inertia

Je=0.025 kgm2

Machine drag coefficient

Ce=3x10-5 ? Nm

Load torque

Tm=0.1? Nm

Load inertia

Jm=0.1 kgm2

Load drag coefficient

Cm=1x10-5 ? Nm

The connecting shaft between the motor and load can be assumed to be stiff with zero inertia.

(i) Sketch the free body diagram of the motor and load system.

(ii) Derive the mechanical system equation including all torques, inertias and losses acting upon the system.

(iii) Calculate the steady-state speed and the mechanical time constant of the system.

(iv) Derive the equation relating speed and time.

(v) Calculate the time taken for the machine to reach 50% of its steady-state speed.

(b) An electrical machine is connected to a mechanical load. The system has the following mechanical parameters: Electrical torque developed

Te = 48-0.32? Nm

Machine inertia

Je=0.025 kgm2

Machine drag coefficient

Ce=3x10-5 ? Nm

Load torque

Tm=0.1? Nm

Load inertia

Jm=0.1 kgm2

Load drag coefficient

Cm=1x10-5 ? Nm

a2 (a) A separately Dc machine is used to drive a conveyor belt. The armature has the excited electrical parameters va 12ov, R.-20, La 10mH, the field current le 10A and the mutual inductance L 80mH (i) ketch the equivalent circuit and derive the electrical equation describing the armature circuit (ii) Derive the steady-state voltage and torque equations. (iii) use your equations from part (ii) to derive an equation linking torque and speed. (iv) sketch torque-speed profile of this machine on a graph. You are not required to use the graph paper, but your sketch should be accurately and carefully drawn. (b) An electrical machine is connected to a mechanical load. The system has the following mechanical parameters: Electrical torque developed Te 48-0.32w Nm Je-0.025 kgm Machine inertia Machine drag coefficient c 3x10 w Nm Tm 0.1w Nm Load torque Jm 0.1 kgm Load inertia cm 1x105 w Nm Load drag coefficient The connecting shaft between the motor and load can be assumed to be stiff with zero inertia. sketch the free body diagram of the motor and load system. acting (ii) Derive the mechanical system equation including all torques, inertias and losses upon the system. constant of the system. (iii) Calculate the steady-state speed and the mechanical time (iv) Derive the equation relating speed and time. its steady-state speed. (v) Calculate the time taken for the machine to reach 50% of

Explanation / Answer

INCREASES - The number of particles in the system increases, i.e. the single reactant dissociates into two ion particles. In addition, the ions in the ionic solid are organized in a rigid lattice structure whereas the ions in aqueous solution are free to move randomly through the solvent.

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