Dc Motor
AC Motors vs DC Motors DC Motors
Prof. Dr. M. Zahurul Haq zahurul@me.buet.ac.bd http://teacher.buet.ac.bd/zahurul/
Department of Mechanical Engineering Bangladesh University of Engineering & Technology e316.eps ME 475: Mechatronics
AC motors are smaller in size, reliable and less costly. AC motors run at fixed speed set by the line frequency. Easy speed, torque & direction controls in DC motors. DC motors are generally operate at lower voltages which makes these easier to interface with control electronics.
DC Motors ME 475 2 / 39
c Prof. Dr. M. Zahurul Haq (BUET)
DC Motors
ME 475
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c Prof. Dr. M. Zahurul Haq (BUET)
DC Motor Classification
DC motors can be divided into two general categories:
1
...
Brush-type DC Motor: has a mechanical brush pair on the motor frame & makes contact with a commutator ring assembly on the rotor in order to communicate current, i.e. to switch current from one winding to another, as a function of rotor position so that the magnetic fields of the rotor & stator are always at a 90o angle relative to each other. Brushless DC Motor: is an inside-out version of the brush-type DC motor, i.e. the rotor has the permanent magnets & the stator has the winding. Hence, magnetic fields of the rotor & stator must be perpendicular to each other at all rotor positions. Communication is done by solid-state power transistors based on a rotor position sensor, hence it is considered a servo motor. c Prof. Dr. M. Zahurul Haq (BUET) e364.eps
2
c Prof. Dr. M. Zahurul Haq (BUET)
DC Motors
ME 475
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DC Motors
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Brush-type DC motors have the permanent magnet (PM) as the stator (typically 2-pole or 4-pole configuration) & the windings on the iron core rotor. Almost identical mechanical components exist in the brushless DC motors with 3 exceptions:
1
PM DC Motor
2
3
There are no commutator or brushes since commutation is done electrically by the drive. The rotor
Prof. Dr. M. Zahurul Haq zahurul@me.buet.ac.bd http://teacher.buet.ac.bd/zahurul/
Department of Mechanical Engineering Bangladesh University of Engineering & Technology e316.eps ME 475: Mechatronics
AC motors are smaller in size, reliable and less costly. AC motors run at fixed speed set by the line frequency. Easy speed, torque & direction controls in DC motors. DC motors are generally operate at lower voltages which makes these easier to interface with control electronics.
DC Motors ME 475 2 / 39
c Prof. Dr. M. Zahurul Haq (BUET)
DC Motors
ME 475
1 / 39
c Prof. Dr. M. Zahurul Haq (BUET)
DC Motor Classification
DC motors can be divided into two general categories:
1
...
Brush-type DC Motor: has a mechanical brush pair on the motor frame & makes contact with a commutator ring assembly on the rotor in order to communicate current, i.e. to switch current from one winding to another, as a function of rotor position so that the magnetic fields of the rotor & stator are always at a 90o angle relative to each other. Brushless DC Motor: is an inside-out version of the brush-type DC motor, i.e. the rotor has the permanent magnets & the stator has the winding. Hence, magnetic fields of the rotor & stator must be perpendicular to each other at all rotor positions. Communication is done by solid-state power transistors based on a rotor position sensor, hence it is considered a servo motor. c Prof. Dr. M. Zahurul Haq (BUET) e364.eps
2
c Prof. Dr. M. Zahurul Haq (BUET)
DC Motors
ME 475
3 / 39
DC Motors
ME 475
4 / 39
...
Brush-type DC motors have the permanent magnet (PM) as the stator (typically 2-pole or 4-pole configuration) & the windings on the iron core rotor. Almost identical mechanical components exist in the brushless DC motors with 3 exceptions:
1
PM DC Motor
2
3
There are no commutator or brushes since commutation is done electrically by the drive. The rotor