Permanent Magnet Synchronous motor drives

ByASISH KUMAR MONDAL

(UNIVERSITY REGISTRATION NUMBER - 210608010)

UNDER THE GUIDANCE OF

Dr. KAUSHIK MUKHERJEE Dr. MAINAK SENGUPTA

A Term paperSubmitted in partial fulfillment of the requirements

For the degree of MASTER OF ENGINEERING (Electrical Engineering)

(Specialization: POWER ELECTRONICS)

Department Of Electrical EngineeringBENGAL ENGINEERING AND SCIENCE UNIVERSITY, SHIBPUR

HOWRAH – 711 103.WEST BENGAL,INDIA.

Bengal Engineering and Science University, ShibpurHowrah – 711 103West Bengal, India

I hereby forward the Progress Report entitled “Permanent Magnet Synchronous motor drives ” submitted by Sri Asish Kumar Mondal (Registration No. 210608010 of 2008-2009) under my guidance and supervision in partial fulfillment of the requirements for the degree of Master of Engineering in Electrical Engineering (Specialization: Power Electronics) from this University.

-------------------------------

(Project Supervisor)

[Dr. KAUSHIK MUKHERJEE]

------------------------------- (Project. Supervisor)

[Dr. MAINAK SENGUPTA]

Countersigned by:

----------------------------- (Dr. S.K.MALLIK) Professor & Head

Department of Electrical Engineering,Bengal Engineering and Science university, Shibpur

Howrah-711103

--------------------------( Dr. A.K.DAS )

Dean, FEAT,Bengal Engineering and Science university , Shibpur Howrah-711103

Bengal Engineering and Science University, Shibpur

Department of Electrical EngineeringHowrah- 711103 (West Bengal)

CERTIFICATE OF APPROVAL

The forgoing progress report is hereby approved as a creditable study of an engineering subject carried out

and presented in a manner satisfactory to warrant its acceptance as a prerequisite for the THESIS WORK

for which it has been submitted. It is understood that by this approval the undersigned does not necessarily

endorse or approve any statement made, opinion expressed or conclusion drawn therein but approve the

progress report only as a prerequisite for the THESIS WORK.

Board of Examiners:

1)………………………………………..

2)………………………………………..

BENGAL ENGINEERING & SCIENCE UNIVERSITY

Howrah – 711103West Bengal

Acknowledgement

I would like to express my deep sense of gratitude towards Dr. KAUSHIK MUKHERJEE

and Dr. MAINAK SENGUPTA of Bengal Engineering and Science University for their

guidance and help. I am privileged working under them.

I am very thankful to Dr. PRASID SYAM who has helped me in every

possible way. I also want to express my gratitude towards Prof S.K.MALLIK, head of the

Department of Electrical Engineering for providing necessary facilities for carrying out

the work. I would also like to thank the staffs of Bengal Engineering and Science

University Library for providing me the Library facility at all times.

I also thankfully acknowledge the assistance received from my friends and

others for their cooperation during the preparation of the Progress Report.

Date: (ASISH KUMAR MONDAL)Place: Bengal Engineering and Science University , Shibpur Roll No.160806010

Howrah: 711103 Reg. No. 210608010 Master of Engineering

Electrical Engg. Dept. B. E. S. U., Shibpur

Howrah – 711103

CONTENT

1. INTRODUCTION

2. Permanent Magnet Synchronous Motor Drives

3. Modeling of PMSM

4. CONCLUSION

5. Hands on experience with DSP TMS320LF2407

INTRODUCTION

In recent years, Permanent Magnet Synchronous Motors (PMSM) are increasingly applied in several areas such as traction, automobiles, robotics and aerospace technology. The growth in the market of PM motor drives has demanded the need of simulation tools capable of handling motor drive simulations. Simulations have helped the process of developing new systems including motor drives, by reducing cost and time. Simulation tools have the capabilities of performing dynamic simulations of motor drives in a visualenvironment so as to facilitate the development of new systems. Accurate simulation are necessary to evaluate their performance particularly when they are driven with solid-state drives connected to larger electrical networks. One of the areas of interest is the design of controllers for these motor drives. In many applications the physical controls have to be designed and tuned for best performance.

Permanent Magnet Synchronous Motor

The PM Synchronous motor is a rotating electric machine where the stator is a three phase stator like that of an induction motor and the rotor has surface-mounted permanent magnets. In this respect, the PM Synchronous motor is equivalent to an induction motor where the air gap magnetic field is produced by a permanent magnet. The use of a permanent magnet to

generate a substantial air gap magnetic flux makes it possible to design highly efficient PM motors.

Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor Drives

Permanent Magnet Synchronous Motor Drives consists of four main components, the PM motor, inverter, control unit and the position sensor.

Figure1: Drive System Schematic

Modeling of PMSM

Modeling of PM motor drive system is required for proper simulation of the system. The d-q model has been developed on rotor reference frame as shown in figure 2 .At any time t, the rotating rotor d-axis makes and angle θr with the fixed stator phase axis and rotating stator mmf makes an angle α with the rotor d-axis. Stator mmf rotates at the same speed as that of the rotor.

Figure 2: Motor Axis

The model of PMSM without damper winding has been developed on rotor reference frame using the following assumptions:

1) Saturation is neglected. 2) The induced EMF is sinusoidal.3) Eddy currents and hysteresis losses are negligible. 4) There are no field current dynamics.

Voltage equations are given by:

………………………………….1

……………………………….2

Flux Linkages are given by

………………………………………….……..3

…………………………………………….4

Substituting equations 3 and 4 into1 and 2

Equivalent Circuit of Permanent Magnet Synchronous Motor

Equivalent circuits of the motors are used for study and simulation of motors. From the d-q modeling of the motor using the stator voltage equations the equivalent circuit of the motor can be derived. Assuming rotor d axis flux from the permanent magnets is represented by a constant current source as described in the following equation

Figure: 3 Permanent Magnet Motor Electric Circuits without Damper Windings

Parks Transformation and Dynamic d q Modeling

The dynamic d q modeling is used for the study of motor during transient and steady state. It is done by converting the three phase voltages and currents to dqo variables by using Parks transformation Converting the phase voltages variables abc to dqo variables in rotor reference frame the

following equations are obtained

Inverter Operation

Fig 4. Voltage source inverter

For 180 conduction mode and 6-1-2 switching

similar way for 6-1-2 , 1-2-3, 2-3-4, 3-4-5, 4-5-6, 5-6-1 switching we can construct this figure

fig 5: orientation of resultant flux linkage for different switching

Switching Vd Vq

6-1-2

1-2-3

2-3-4

3-4-5

4-5-6

5-6-1

Steady state analysis

Flux Linkages are given by

…………………………………………...5

………………………………………6

…………………………….7

……………………….8

………………………9

Constant torque control strategy is derived from field oriented control, where the maximum possible torque is desired at all times like the dc motor. This is performed by making the torque producing current iq equal to the supply current Im. That results in selecting the α angle to be 90 º degrees according

to equation 15. By making the id current equal to zero the torque equation can be rewritten as:

……………………………………….6

Assuming that:

……………………………………………7

The torque is give by

……………………………………………………….8

Like the dc motor, the torque is dependent of the motor current.

CONCLUSION

For Induction motor, Stator current has two component one in magnetizing component and other in torque producing component But for PMSM, stator current caring only torque producing component of current. Due to magnetizing component of current losses will increase for induction machine. So for same rating and operation PMSM will have higher efficiency than Induction machine For conventional dc machine, maintenance is required for bras and commutator but for BLDC, maintenance cost for bras and commutator is zero . For those advantageous feature, BLDC become very popular.