Example Application
We must use 10 hp, 1760 r/min, 440 V, 3 phase induction motor as an asynchronous generator. Full-load current of the motor is 10 A and full-load power factor is 0.8.
Required capacitance per phase if capacitors are connected in delta:
- Apparent power S = √3 E I = 1.73 * 440 * 10 = 7612 VA
- Active power P = S cos θ = 7612 * 0.8 = 6090 W
- Reactive power Q = = 4567 VAR
For machine to run as an asynchronous generator, capacitor bank must supply minimum 4567 / 3 phases = 1523 VAR per phase. Voltage per capacitor is 440 V because capacitors are connected in delta.
- Capacitive current Ic = Q/E = 1523/440 = 3.46 A
- Capacitive reactance per phase Xc = E/I = 127 Ω
Minimum capacitance per phase:
- C = 1 / (2*π*f*Xc) = 1 / (2 * 3.141 * 60 * 127) = 21 microfarads.
If load also absorbs reactive power, capacitor bank must be increased in size to compensate.
Prime mover speed should be used to generate frequency of 60 Hz:
Typically, slip should be similar to full-load value when machine is running as motor, but negative (generator operation):
- Slip = 1800 - 1760 = 40 rpm
- Required prime mover speed N = 1800 + Slip = 1840 rpm.
Read more about this topic: Induction Generator
Famous quotes containing the word application:
“It is known that Whistler when asked how long it took him to paint one of his “nocturnes” answered: “All of my life.” With the same rigor he could have said that all of the centuries that preceded the moment when he painted were necessary. From that correct application of the law of causality it follows that the slightest event presupposes the inconceivable universe and, conversely, that the universe needs even the slightest of events.”
—Jorge Luis Borges (1899–1986)
“The application requisite to the duties of the office I hold [governor of Virginia] is so excessive, and the execution of them after all so imperfect, that I have determined to retire from it at the close of the present campaign.”
—Thomas Jefferson (1743–1826)