2007-02-08 02:33:05 · 4 answers · asked by peterphillips.php@btinternet.com 1 in Science & Mathematics ➔ Engineering
Assuming the machine has been tested, there is a slight residual magnetism in both the rotor steel and the stator steel.
Applying three-phase current to the stator winding will generate a magentic force proportional to the amplitude of the current and the number of turns in the winding. Because it is an AC signal, this magnetic field will move circumferentially around the stator based on the phase pattern of the winding (A-B-C gives one rotation, A-C-B gives the other).
Two other things occur simultaneously; the rotor's residual magentism starts it passing through the lines of flux generated by the stator winding (following the AC signal around the stator), and the passage of the rotor winding through the stator field generates a current in the rotor winding.
With current in the rotor winding, the rotor increases its magnetic strength, allowing the machine to generate noticeable torque (due to the interaction of the two magnetic fields - stator and rotor).
The inrush current is the current drawn by the stator winding during startup and acceleration, as the stator does the extra 'work' of energizing the rotor field.
Once the machine is up to speed (slightly less than a true synchronous speed, due to rotor 'slip'), the inrush drops away to zero and you now have load torque occurring with load current drawn by the stator winding.
2007-02-08 06:41:11 · answer #1 · answered by CanTexan 6 · 0⤊ 0⤋
The second answer is the best. There are various different induction motor starters . Direct on Line. Auto Transformer. Star Delta. There are also newer soft start methods all designed to reduce the starting current to acceptable levels.
2007-02-09 21:37:26 · answer #2 · answered by Anonymous · 0⤊ 0⤋
As soon as power is applied to a three phase motor, a rotating magnetic field is produced by the stator and the rotor begins rotating. Simple like that.
2007-02-08 12:46:21 · answer #3 · answered by Paulo M G C 6 · 0⤊ 0⤋
electrical engergy is generated by a rotating machine which creates a sinusoidal or rotating electrical field.
induction motors reverse this process using the electrical energy to rotate.
see three phase electric on wikipedia
2007-02-08 17:00:39 · answer #4 · answered by Mark G 2 · 0⤊ 0⤋