Slide 1

--Rishabh ShuklaDC MOTOR & ITS CONTROL

CONTENTS:-Parts of Motor.Basic of OperationTypes of AC MotorTypes of DC MotorDesign ParametersElectrical AnalysisSwitching CircuitSpeed ControlTorque Control Motion Profile

PARTS OF DC MOTOR:-

1. Yoke

2. Pole

3. Field Winding4. Armature Winding5. Commutator & Brush

Converts direct current(electrical energy) into mechanical energy.Extensively used in Industry & vital for Engineers.

*TWO EQUAL AND OPP FORCE CONSTITUTE TORQUE*

BASIC OPERATION:-

ParametersSynchronousInductionSlipNo ~InterlockingYes~ Phase differenceExcitationDouble (Armature+Field)SingleApplicationTimer/ Tape Recorders90% of Industrial motorsPrincipleInteraction of B Field of Stator & Rotor.I flows in statorinduces B Field.

Types of AC Motor :-

ParametersBrushBrushlessCommutation MechanismMechanical using BrushVia Electronic Switching CircuitMechanical FrictionYesNoArcing/ SparksYesNoMax Speed Limited by BrushGreaterThermal CharacteristicsDifficult (Electromagnet is on Rotor)Improved thermal characteristics.Motion PrecisionLessMore System WeightMoreLess

Types of DC Motor On the basis of Commutation:-*THE ACT OF CHANGING DIRECTION OF CURRENT IS CALLED COMMUTATION*

*DESIGN PARAMETERS:-ParametersDefinition1Stall TorqueIs the torque produced by the motor when at standstill.2Nominal TorqueIs the torque generated for operation at nominal voltage and nominal current at temp of 25 degree C3Speed/Torque GradientIndicator of Motor Performance. Smaller the value more powerful the motor. It is quotient of no load speed and ideal stall torque.4Mechanical Time constTime required for rotor to accelerate form standstill to 63% of its no load speed5Nominal VoltageIs the applied voltage between two powered phases in bolck commutation mode6Thermal time constantTypical reaction time for a temperature change of winding and motor

Electrical Analysis of a DC Motor

Where, P = no of poles = flux per poleZ= No. of conductorsA = No. of parallel pathsand N is the speed of the DC Motor.

Ebis proportional to speed N.So when the speed of the motor is reduced by the application of load, Ebdecreases.means E Eb increases.Due to this increasedvoltage difference, armature current will increase and therefore torque and hence speed increases. Thus a DC Motor is capable of maintaining the same speed under variable load.

As a result we need to use a starter for starting a DC Motor.NEED OF STARTERS:-

Based on the position of the motor (identified using feedback sensor) two of the three electrical windings are energized at a time.External circuit should be able to meet the current requirement of motor.Switching Action cause the Stators B to rotate. --- Bidirectional Currents are produced. A total of six switches are needed for one BLDC motor.*SWITCHING CIRCUIT:-

The Motor Speed depends on the amplitude of applied voltage, which is adjusted using Pulse Width Modulation (PWM)

By controlling the duty cycle of the PWM signal . The amplitude of the applied voltage can be controlled, which in turn will control the speed of the motor.

*SPEED CONTROL:-

* MAXIMUM PERMISSIBLE SPEED :-Max Speed is limited by the commutation systemAt very high speed, commutators and brush wear more rapidly, causing reduce in life of motor.At high speed arcing is more pronounced.

Mn- Rated Torque.Tw- Thermal time constant

Where, P is no of poles, is flux per pole,Z is no. of conductors,A is no. of parallel paths,and N is the speed of the D.C. motor.

*TORQUE CONTROL:-

1. TRIANGULAR:-2. TRAPEZOIDAL:-

More rapid the changein acceleration, the more powerful thevibrations will be*MOTION CONTROL:-JERK= CHANGE IN ACCLERATION TIME

3. S -Type:-

Induced vibration for S curve and trapezoidal mode.4. VIBRATION IN SYSTEM:-*VIBRATION ANALYSIS:-

*CHALLENGES:-TO KNOW THE KEY REQUIREMENTS OF FORCES/ TORQUES and VELOCITIES (SPEED OF ROTATION)??

HOW LONG THEY MUST BE APPLIED??

DESIGN A DRIVING MECHANISM BY CALCULATING THE MOMENT OF INERTIA OF ROTATING LOAD.

GEARHEAD DESING

CHOOSE BETWEEN AVALIABLE MOTORS.

SENSOR CONTOLLER

COST CONSIDERATION

*REFERNECE:-Maxon MotrosElectrical For youWikipedia