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[edit] Electric Motors[edit] Technology[edit] AC Motors[edit] Induction Motors[edit] Slip Ring MotorsSlip ring motors or wound rotor motors are a variation on the standard cage induction motors. The slip ring motor has a set of windings on the rotor which are not short circuited, but are terminated to a set of slip rings for connection to external resistors and contactors. The slip ring motor enables the starting characteristics of the motor to be totally controlled and modified to suit the load. A particular high resistance can result in the pull out torque occurring at almost zero speed providing a very high locked rotor torque at a low locked rotor current. As the motor accelerates, the value of the resistance can be reduced altering the start torque curve in a manner such that the maximum torque is gradually moved towards synchronous speed. This results in a very high starting torque from zero speed to full speed at a relatively low starting current. This type of starting is ideal for very high inertia loads allowing the machine to get to full speed in the minimum time with minimum current draw.
The down side of the slip ring motor is that the sliprings and brush assemblies need regular maintenance which is a cost not applicable to the standard cage motor. If the rotor windings are shorted and a start is attempted, i.e the motor is converted to a standard induction motor, it will exhibit an extremely high locked rotor current, typically as high as 1400% and a very low locked rotor torque, perhaps as low as 60%. In most applications, this is not an option.
Another use of the slipring motor is as a means of speed control. By modifying the speed torque curve, by altering the rotor resistors, the speed at which the motor will drive a particular load can be altered. This has been used in winching type applications, but does result in a lot of heat generated in the rotor resistors and consequential drop in overall efficiency. [edit] Synchronous Motors[edit] Servo Motors[edit] Schrage MotorsThe Schrage Motor is a very special motor with a brush/commutator fed rotor and a slip ring fed rotor and a wound stator, and due to the way it is constructed is able to be speed controlled by variation of the position of the brushes relative to the field windings. The rotor has two windings, one of which is driven by the commutator/brush assembly and the other is driven by means of slip rings. These motors are usually of European origin and found of some of the older machines imported for specialized applications such as carpet making. [edit] DC Motors[edit] Shunt Wound Motors[edit] Series Wound Motors[edit] Compound Wound Motors[edit] Brushless DC Motors (BLDC)[edit] Universal Motors[edit] Internal LinksInduction Motors [edit] External Links
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Electric Motors
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