AVTC Model Based Design Curriculum Development Project

Lesson 1: Basic Machine Concepts

Main Components of All Electric Machines The principal structure is a rotor and a stator that function as a result of the interaction of magnetic fields and currents −Stator: stationary shell that is designed to produce a magnetic flux and houses the rotor −Rotor: rotates inside the stator Rotor Stator Illustrated by: Zureks

Principle of Electric Machines Brushed DC Motor Brushless DC Motor Induction Motor Source:

Principle of Brushed DC Motors N Armature windings are located on rotor Stator magnetic field produced by either a permanent magnet or an electromagnet resulting from DC current in stator winding Current to rotor supplied through brushes in contact with commutator segments Interaction of field and current generate a rotational force (torque) to drive the motor S S Source:

Principle of Brushless DC Motors Armature windings are on stator Permanent magnets located on rotor Commutator replaced by electronic switches Hall effect sensors detect the rotor’s angular position to control electronic switches Source: Source:

Hall Effect Sensor Device + Current – Electron Path q v F B

Principle of Brushless DC Motors (Cont’d) PMDC Motor Position Sensor Inverter Logic Circuit Electronic Commutator + - V

Why is a Brushless DC motor called a DC motor if it’s an AC motor? Both require a commutator but in brushless DC motor commutating action is done electronically where as in brushed DC motor it is done mechanically A BLDC has feedback that identifies position of rotor with the help of some sensor techniques Brushless DC motors produce a voltage waveform similar to a brushed DC motor ? ? ? ?

Why DC if AC? (Cont’d…) Brushless DC Motor Trapezoidal EMF Wave Brushed DC Motor Sinusoidal EMF Wave

Principle of Induction Machines 3- Φ AC power is supplied to the stator windings producing a rotating magnetic field Stator field induces ac current in rotor somewhat similar to a transformer Rotor speed lags the stator field rotational speed by what is known as slip Torque produced is related to the slip. Interestingly, zero torque would be produced if it were at synchronous speed (speed of the rotating stator field) Source:

Basis of Operation of All Rotating Machines Motor – Magnetic attraction and repulsion forces generate mechanical torque Generator – Time varying magnetic field induces voltage in windings by Faraday’s law

Modeling of a DC Motor Now let’s develop a very simple model of an electric motor using the basic torque equation………. But first, …What is TORQUE?

Torque Distance Force Torque Torque provides a force at the interface between the tire and the road r

Development of a Simulink Model for a DC Motor Ti T θ i

Introduce Simulink Blocks You will need the following blocks to model torque:

Constant Block Double click on block and change the constant value to this:

Gain Block Change your Gain amount to:

Introduce Simulink Modeling Connect blocks together and add a display at the end. Enter the following in the Command Window: – I=0.2; Kt=.01; Click the run button in the model file The output torque of m-N is shown in the display block above

Review 1.What are the main components of ALL electric machines? (choose all that apply) a.Stator b.Armature windings c.Permanent magnets d.Rotor 2.There is a commutator in all electric machines. a.True b.False 3.Torque is proportional to which of the following in a DC motor (Choose all that apply) a.Armature current b.Magnetic field c.None of the above

References Yedamale, P., “Brushless DC (BLDC) Motor Fundamentals,” Microchip Technology. DS00885A Nov “Brushed DC Motors,” brushed.html. “Brushless DC Motors”, 95DE1. “Induction Motor”, Feb

References Cont’d Bosch GmbH, Robert, “Automotive Electrics, Automotive Electronics,” Bentley, Cambridge, MA, , Ehsani, Mehrdad Yimin Gao, Ali Emadi and Sebastien E. Gay, “Modern Electric, Hybrid Electric, and Fuel Cell Vehicles: Fundamentals, Theory, and Design,” Boca Raton: CRC, , Ehsani, Mehrdad, Yimin Gao, and Ali Emadi, “Modern Electric, Hybrid Electric, and Fuel Cell Vehicles: Fundamentals, Theory, and Design,” Boca Raton: CRC, 312, Husain, Iqbal, “Electric and Hybrid Vehicles: Design Fundamentals. 2nd ed.,” Boca Raton, FL: CRC, 2011.