A Y-connected 3-phase induction motor given below is supplied from a 480V l - l,
ID: 2080751 • Letter: A
Question
A Y-connected 3-phase induction motor given below is supplied from a 480V l - l, 60Hz source. It is connected to a load that has T_L = 170 middot 10^-6 omega^2, with omega in rad/s. Using a simple machine model calculate speed and efficiency at the operating point. Using a complete machine model calculate: starting torque. efficiency at the point you found a the previous step. Maximum torque (pull-out torque and the speed at which it occurs.) The motor starts by directly connecting to rated voltage, and the shaft connected to a load. Prepare a Matlab program (or a Simulink one if you prefer). Simulate the motor startup and plot speed and amplitude of current. Using the program you prepared compute time to reach 88% of the equilibrium. Integrate input power and losses, plot them v. time, and compute total energy input and energy losses until the motor reaches that point. J = 160kg m^2, R_R = 0.5Ohm, R_s = 0.15Ohm, L_m = 250mH, L_is = L_lr = 6.2mH.Explanation / Answer
1) Given Parameter
Voltage = 480v
Frequency = 60 Hz
Speed and efficiency at the operating point.
Speed = V/f +TL
= 480/60 * 170.10
= 1360 ms.
(2)
(a) Starting Torque-- The torque developed by an asynchronous induction mtor varies when the motor accelerates from zero t maximum operating point.
(b) Maximum Torque ( Pull out torque and the speed at which it occurs)
The full load torque is the torque required to produce the rated power of an electrical motor at full load speed.
In metric units, the full load torque can be expressed as-
T = 5252 Php/hour
Where T = full load torque ( lb ft)
Php = Rated hore power
nr = Rated Rotational Speed
In metrics units, the rated torque can be expressed as-
T = 9550 Pkw/nr
Where
T = Rated Torque (Nm)
Pkw = Rated Power
nr = Rated Rotational Speed.
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