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Group 2 Broussard, David Holcomb, Nick Reinhart, Lynne Watson, Robert
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Break it down. The rotor and stator are electromagnets.
An induction motor's speed is controlled by the frequency of electricity going to it (hertz), so most induction motors have a fixed speed. Induction motors Often these motors are used in industrial applications. Multiphase motors are rugged and brushless. Single phase induction motors are widely used in small appliances
How they work • Induction and synchronous motors often have a stator, and they are designed to create a rotating field which rotates in time with the alternating current oscillations. • In an induction motor the rotor rotates slightly slower than the stator field (lagging behind). • The rotor and magnetic field are rotating and creating magnetic flux, thus inducing current in the windings of the rotor
How they act • The motor acts similar to a transformer, pulling magnetic flux and turning into useable current. Magnetic flux Transformers
The current in the rotor creates a magnetic field which works against the magnetic field of the stator and creates movement. Negative Positive • Lenz's law states that the magnetic field will try to oppose a change in current, thus making the direction of rotation synchronize with the stator.
What’s the difference? • There is a difference of speed / lag because if the poles were directly lined up they would be creating no torque. Full load slip varies from less than 1% in high power motors to more than 6% in smaller motors.
Why is that? • As the speed of the rotor slows below synchronous speed, the rotation rate of the magnetic field in the rotor increases thus inducing more current and more TORQUE. • There is little slip when under full load on large motors.
Smaller induction motor Smaller induction motors are used for many things. This is on my wish list!
History • Original Tessla motor circa 1887. Strangely, AC current induction motors seem to have been invented by both Nikola Tesla and Galileo Ferraris independently in the late 1880s.
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Stepper motors Stepper motors have no brushes! Notice the teeth, they are the ‘steps’.
How they work • The stepper motor is a brushless DC electric motor that divides one full rotation into a number of equal steps. • The motor position can then be programmed to move and hold at one of these steps.
Control system! • The indexer, or controller, is a microprocessor that generates direction signals for the driver. • The driver, or amplifier, generates the controller pulses into power needed to energize the motor windings. • Last but not least, the stepper motor itself! It steps -you better believe it!
Some are very small! • They are so precise they are used in laser and optic applications
They move things in stages Stepper motors help track the sun.
Where they shine • Low cost, high reliability, high torque at low speeds and a simple, rugged construction that operates in almost any environment. Weaknesses • Stepper motors have a resonance effect often exhibited at low speeds and decreasing torque with increasing speed. They provide limited feedback.
Also found in • Robotics!
Arrays! Radio Controlled devices!
Thank you~! Feel free to check out these additional induction motor links: http://en.wikipedia.org/wiki/Polyphase_system http://www.youtube.com/watch?v=HWrNzUCjbkk