ET 332a Dc Motors, Generators and Energy Conversion Devices 1.

Slides:



Advertisements
Similar presentations
ENERGY CONVERSION ONE (Course 25741)
Advertisements

Chapter 6 DC and AC Machines
EEEB443 Control & Drives Modeling of DC Machines By
DC Motors electrical machine1 J 2006.
Basics of a Electric Motor
Power System Fundamentals
DC Motors KL3073.
3. ARMATURE VOLTAGE AND GOVERING EQUATIONS
Dr. Nik Rumzi Nik Idris Dept. of Energy Conversion, UTM 2013
ELECTRIC DRIVES Ion Boldea S.A.Nasar 1998 Electric Drives.
Elec467 Power Machines & Transformers
SEE 3433 ELECTRICAL MACHINES Classification of DC machines DC Generators - Separately excited - Armature reaction.
EE 306 DC MACHINES Hatem Al-Ghannam
Lesson 37 AC Generators II
Lesson 33 AC Generators.
Induced emf Developed torque Magnetization curve SEE 3433 ELECTRICAL MACHINES.
ET 332a Dc Motors, Generators and Energy Conversion Devices Lesson 2: Magnetic Circuits- Quantities and Definitions 1.
DC Motor - 2 BEE2123 ELECTRICAL MACHINES
Lesson 11: Separately Excited Motor Examples
BASIC ELECTRICAL TECHNOLOGY DET 211/3
ET 332A DC MOTORS, GENERATORS AND ENERGY CONVERSION DEVICES Lesson 7: Construction of Elementary Dc Generators 1.
ET 332a Dc Motors, Generators and Energy Conversion Devices 1Lesson a.pptx.
Lesson 17: Other Dc Motor Connections
Lesson 10: Separately Excited Dc Motors
Synchronous Generator
ET 332a Dc Motors, Generators and Energy Conversion Devices 1.
ENERGY CONVERSION ONE (Course 25741) CHAPTER NINE ….continued DC MOTORS AND GENERATORS.
ET 332a Dc Motors, Generators and Energy Conversion Devices 1Lesson a.pptx.
ENERGY CONVERSION ONE (Course 25741)
ET 332a Dc Motors, Generators and Energy Conversion Devices 1Lesson a.pptx.
Lesson 19: Non-Linear Operation of Dc Motors ET 332a Dc Motors, Generators and Energy Conversion Devices 1Lesson a.pptx.
DC motor model ETEC6419. Motors of Models There are many different models of DC motors that use differential equations. During this set of slides we will.
ET 332a Dc Motors, Generators and Energy Conversion Devices 1 Lesson a.pptx.
ET 332a Dc Motors, Generators and Energy Conversion Devices 1Lesson a.pptx.
DC GENERATOR CHAPTER-9.
Chapter 16 DC Generators.
ET 332a Dc Motors, Generators and Energy Conversion Devices 1 Lesson a.pptx.
Department of Electrical and Computer Engineering EE20A - Electromechanical Energy Conversion DC Machine.
DC MACHINE SHAIFUL NIZAM MOHYAR 2007/2008 UNIVERSITI MALAYSIA PERLIS
EEE1012 Introduction to Electrical & Electronics Engineering Chapter 9: Introduction to Electric Machines by Muhazam Mustapha, October 2010.
Electromagnetic Induction Create electric current from changing magnetic fields.
Chapter 6 DC Machines EET103/4.
Direct-current motor is a device that transforms the electrical energy into mechanical energy. There are five major types of dc motors in general use:
Magnetic field due to an electric current
DC Machines.
DC Machines.
ELEC 3105 Basic EM and Power Engineering Rotating DC Motor PART 2 Electrical.
Speed Control in DC Motors
DC MACHINE Hasnizah Aris.
BASIC ELECTRICAL TECHNOLOGY DET 211/3
DC Machine A Presentation on Submitted to : Department of Electrical Engg. Atmiya Institute of Tech. & Sci. Rajkot (003)
Akshay Thakur Electrical-B 3 rd sem.
DC Motor For students of the second stage in the Department of Electrical Engineering Introduction by Salam Mohammed Atiyah Master of Electrical Engineering.
DC GENERATORS Introduction The outstanding advantages of dc machines arise from the wide variety of operating characteristics which can be obtained by.
DC Motor.
DC Motor Dave Hardi En No: KIT, Jamnagar.
Lesson 12a: Three Phase Induction Motors
DC MOTORS AND GENERATORS
BASIC ELECTRICAL TECHNOLOGY DET 211/3
CHAPTER 2 DC GENERATOR Electrical Machines.
DC GENERATORS G H PATEL COLLEGE OF ENGINEERING & TECHNOLOGY
DC Generators.
DC Generators.
ELEC 3105 Basic EM and Power Engineering
Electric Machine DC Generator (2)
Electric Machine DC Generator (3)
Chapter 6: DC & AC Machine
DC Machines Fundamentals
Chapter 29 D.C. Motor. Chapter 29 D.C. Motor D.C. Motor C-29 Motor Principle Comparison of Generator and Motor Action Significance of the Back e.m.f.
CHAPTER 2: DC DRIVES (Part 3)
Presentation transcript:

ET 332a Dc Motors, Generators and Energy Conversion Devices 1

Learning Objectives After this presentation you will be able to:  Compute the average output voltage of a dc generator given machine physical construction parameters.  Draw the schematic circuit model of a dc machine  Find generator output voltage using a magnetization curve and defining formulas.  Compute generator voltage regulation. 2

Average Induced Voltage in a Generator 3 Where v = velocity of conductor For rotating system v = angular velocity d  /dt =  rad/s Start with fundamental equation Frequency of e related to number of field poles and rotational speed by: Angular velocity relates to frequency f (cycles/s or Hertz) by:  = 2  f Where: P = number of field poles n = rotational speed (rpm)

4 Average Induced Voltage in a Generator Substituting into fundamental equation and simplifying gives: Where: P = number of poles n = rotational speed N a = # of turns in coil  p = field flux E a = average induced voltage Consider machine construction details and define another voltage formula

5 Average Induced Voltage in a Generator Define the number of conductors in field in terms of windings z a = Total number of armature conductors in the field. Substitute into previous equation to get: Where: a = number of parallel paths

6 Average Induced Voltage in a Generator The number of poles, parallel paths, and conductors are constant once the machine is constructed so define: The constant k G also known as k e in some texts. Relates motor voltage to speed and field flux. Where k G = emf constant Note : E a is proportional to the flux and to the rotational speed. If conditions of machine are know at one n and  p, another operating point can be found by equating ratios.

Induced Voltage Examples 7 Example 1: A 2 pole dc motor armature rotates at 1800 rpm. It has 400 turns in the armature winding. The magnetic field flux is Wb. Compute the average induced voltage. Example 2: A 4 pole dc machine rotates at 200 rad/s in a magnetic field of Wb. There are 4 parallel current paths that have 200 conductors. Find the induced voltage in the armature and the emf constant for the machine. Convert  o n for formula

8 Induced Voltage Examples Example 2 Continued: Find the emf constant Lump the constants and compute Example 3: A 4 pole 50 kW dc machine has a value of E a = 110 V at 1100 rpm. What is the induced voltage if the speed is increased 20%? No change in flux Find E a2 Ans

9 Induced Voltage Examples Example 4: A 4 pole dc machine has a value of E a = 50 V at 400 rpm. What is the value of E a if the pole flux is doubled while the speed remains constant? Assumes no saturation Ans

10 Circuit Model of Dc Machines R acir = dc resistance of the armature windings, interpoles, etc L a = inductance of armature circuit R f = dc resistance of the field windings L f = inductance of the field windings E a = internally induced voltage V t = terminal voltage of machine V f = field electromagnetic source voltage VfVf + EaEa + VtVt + LfLf LaLa RfRf R acir Inductances have no effect when the values of dc current are not changing. Shown to indicate coils.

Generator Circuit Model 11 EaEa + LfLf LaLa RfRf R acir VfVf IaIa VtVt + Generator model - mechanical power converted to electric power. I a leaves the + terminal of armature IfIf Field current produces field flux From KVL around armature circuit Total resistance of armature circuit R acir Where: R a = armature resistance R IP = interpole winding resistance R cw = compensation winding resistance Brush losses P=2 ∙I a 1 volt drop for each brush Brush drop

12 Motor Circuit Model EaEa + LfLf LaLa RfRf R acir VfVf IaIa IfIf Brush drop VtVt + Motor model - electric power converted to mechanical power. I a enters the + terminal of armature Analyze the field circuit Control I f with field rheostat IfIf R c = field coil resistance R f = field rheostat resistance

Separately Excited Dc Generator 13 R acir LaLa EaEa LfLf RcRc RfRf VfVf VtVt N n Separate source of supply develops field flux. Source called the exciter RLRL Model Equations: Field circuit current Magnetic coupling to induced average voltage E a in terms of flux for constant I f pp E a proportional to n for constant I f IfIf

14 Separately Excited Dc Generator Generally flux,  is non-linear with respect to the field current I f. Magnetizing curve for generator gives relationship for E a as a function of field current. If I f is in linear part of curve E a is proportional to n and I f. Field Current, I f (A) Induced EMF, E a (V) k e valid here Generator Magnetizing Curve

Terminal Voltage Regulation 15 Voltage regulation finds the percent change in terminal voltage from no- load to full load VtVt KVL around armature circuit with switch closed IaIa n With switch closed and n constant V t < E a and decreases as I a increases I a = 0 with switch open so:No-load voltage = E a

16 Terminal Voltage Regulation For rated terminal voltage Where:%VR = percent voltage regulation V nl = no-load terminal voltage V rated = name plate rating of the terminal voltage when generator delivers rated power. How does terminal voltage change with delivered power?

17 Terminal Voltage Regulation IaIa EaEa I a, rated V rated V nl R acir Generator Terminal Voltage Vs Load Current Equation above plots as downward sloping line for changes in armature current I a = 0 As armature current decreases (load decreases)Terminal voltage increases (V t increases) %VR related to the armature circuit voltage drop. Smaller %VR is better.

Voltage Regulation Example 18 Example 1 A separately excited 50 kW, 3500 rpm, 2-pole dc generator has a rated terminal voltage of 120 Vdc. Its exciter is supplied from a 120 Vdc supply. The field coil resistance is 10.4  and the field rheostat is set at 20.5 . The total armature resistance is . The generator is supplying 420 A to a load. The magnetizing curve is given on a previous slide. Determine: a.) the induced armature voltage at this level of excitation b.) the terminal voltage at 100%, 75% and 50% load current

Voltage Regulation Solution 19 Draw schematic model for generator Use I f and magnetization curve to find E a E a =162 V I f =3.88 A

20 Voltage Regulation Solution Solution continued: Compute regulation at different load levels

21 Voltage Regulation Solution Solution continued: Compute regulation at different load levels Summary of calculations % LoadIaIa VtVt A A V A V Terminal voltage increases on generator as the load current decreases

22 Example 2: For the machine in Example 1,,determine the field rheostat setting for the machine to deliver rated output current at rated voltage. Also determine the %VR at rated load. Separately Excited Generator Example Solution Calculate the current at rated load for the generator power rating Find Rated I from power and voltage Now find value of E a with V t = 120 V using

23 Separately Excited Generator Example Example 2 Continued Use magnetization curve to find I f E a =162 V I f =3.88 A E a =125.8 V I f =2.8 A I f = 2.8 A from graph. Now find R f Solve for R f

24 Separately Excited Generator Example Example 2 Continued From Previous example Find the % VR Percent Voltage Regulation V nl = V t with I a =0 V nl =

ET 332a Dc Motors, Generators and Energy Conversion Devices 25