Download presentation

Presentation is loading. Please wait.

Published byEssence Stallsworth Modified about 1 year ago

1
Controlled Rectifier DC Drives By Dr. Ungku Anisa Ungku Amirulddin Department of Electrical Power Engineering College of Engineering Dr. Ungku Anisa, July 20081EEEB443 - Control & Drives

2
Outline Power Electronics Converters for DC Drives Controlled Rectifier Fed DC Drives Single Phase Two-quadrant Four-quadrant Three Phase Two-quadrant Four-quadrant References Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives2

3
Power Electronic Converters for DC Drives Speed Control Strategy: below base speed: V a control above base speed: flux control via V f control Power electronics converters are used to obtain variable voltage Highly efficient Ideally lossless Type of converter used is depending on voltage source : AC voltage source Controlled Rectifiers Fixed DC voltage source DC-DC converters Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives3

4
Controlled Rectifier Fed DC Drives To obtain variable DC voltage from fixed AC source DC current flows in only 1 direction Example of a drive system Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives4

5
Controlled Rectifier Fed – Single-phase DC Drives Two-quadrant drive Limited to applications up to 15 kW Regeneration (Q4) only be achieved with loads that can drive the motor in reverse (-ve ) Dr. Ungku Anisa, July 20085EEEB443 - Control & Drives T Q1 Q2 Q3Q4

6
Controlled Rectifier Fed – Single-phase DC Drives Two-quadrant drive For continuous current: Armature voltage where V m = peak voltage Armature current Field voltage Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives6 90 o 180 o Single- phase supply +Va+Va iaia

7
Controlled Rectifier Fed – Single-phase DC Drives Two-quadrant drive For Quadrant 1 operation: positive E a and V a positive a 90 I a positive Rectifier delivers power to motor, i.e. forward motoring. Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives7 90 o 180 o Single- phase supply +Va+Va iaia +Ea+Ea Q1

8
Controlled Rectifier Fed – Single-phase DC Drives Two-quadrant drive For Quadrant 4 operation: negative E a negative a > 90 V a negative I a positive (still in same direction) Rectifier takes power from motor, i.e. regenerative braking. Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives8 90 o 180 o Single- phase supply Va+Va+ iaia Ea+Ea+ Q4

9
Controlled Rectifier Fed – Single-phase DC Drives Four-quadrant drive Converter 1 for operation in 1 st and 4 th quadrant Converter 2 for operation in 2 nd and 3 rd quadrant Limited to applications up to 15 kW Dr. Ungku Anisa, July 20089EEEB443 - Control & Drives T Q1 Q2 Q3Q4 Converter 1Converter 2 Single- phase supply Single- phase supply +Va+Va iaia Two rectifiers connected in anti- parallel across motor armature

10
Controlled Rectifier Fed – Single-phase DC Drives Four-quadrant drive For continuous current: Both converters are operated to produce the same dc voltage across the terminal, i.e.: where and (V m = peak supply voltage) Hence, firing angles of both converters must satisfy the following: Armature current Field voltage Dr. Ungku Anisa, July 200810EEEB443 - Control & Drives +V1+V1 Converter 1Converter 2 V 2 +

11
Controlled Rectifier Fed – Three-phase DC Drives Two-quadrant drive Limited to applications up to 1500 kW Regeneration (Q4) only be achieved with loads that can drive the motor in reverse (-ve ) Dr. Ungku Anisa, July 200811EEEB443 - Control & Drives T Q1 Q2 Q3Q4

12
Controlled Rectifier Fed – Three-phase DC Drives For continuous current: Armature voltage where V L-L, m = peak line-to-line voltage Armature current Field voltage (assuming a three-phase supply is used for field excitation) Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives12 90 o 180 o 3-phase supply +Va+Va iaia

13
Three-phase Controlled Rectifier 2Q DC Drive – Example Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives13

14
Controlled Rectifier Fed – Three-phase DC Drives Four-quadrant drive Converter 1 for operation in 1 st and 4 th quadrant Converter 2 for operation in 2 nd and 3 rd quadrant Dr. Ungku Anisa, July 200814EEEB443 - Control & Drives T Q1 Q2 Q3Q4 Converter 1Converter 2 3-phase supply 3-phase supply +Va+Va iaia Two rectifiers connected in anti- parallel across motor armature I a +ve, V a +ve or -ve I a -ve, V a +ve or -ve

15
Controlled Rectifier Fed – Three-phase DC Drives Four-quadrant drive For continuous current: where V L-L, m = peak line-to-line voltage. Similar to single-phase drive: Dr. Ungku Anisa, July 200815EEEB443 - Control & Drives T Q1 Q2 Q3Q4 Converter 1Converter 2 +Va+Va iaia Converter 1: I a +ve, V a +ve Converter 2: I a -ve, V a +ve Converter 1: I a +ve, V a -ve Converter 2: I a -ve, V a -ve

16
Controlled Rectifier Fed – Three-phase DC Drives For continuous current: Armature current Field voltage Disadvantages: Circulating current Inductors L 1 and L 2 added to reduce circulating currents Slow response Dr. Ungku Anisa, July 200816EEEB443 - Control & Drives +Va+Va Converter 1Converter 2 iaia L1L1 L2L2

17
Three-phase Controlled Rectifier 4Q DC Drive – Example Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives17

18
Controlled Rectifier Fed – Three-phase DC Drives Four-quadrant drive One controlled rectifier with 2 pairs of contactors M1 and M2 closed for operation in 1 st and 4 th quadrant R1 and R2 closed for operation in 2 nd and 3 rd quadrant Dr. Ungku Anisa, July 200818EEEB443 - Control & Drives T Q1 Q2 Q3Q4 M1 M2 R1 R2 + V a - 3-phase supply iaia iaia

19
Rectifier Fed DC Drives Problems 1. Distortion of Supply Controlled rectifier introduces harmonics to supply currents and voltages which cause: heating and torque pulsations in motor resonance in power system network – interaction between rectifier RL with capacitor banks in system Solution - eliminate most dominant harmonics by: install LC filters at input of converters – tuned to absorb most dominant harmonics (i.e. 5 th and 7 th harmonics) Use 12-pulse converter – consists of two 6-pulse controlled rectifiers connected in parallel Selective switching of supply input using self-commutating devices (eg. GTOs, IGBTs) in the converter Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives19

20
Rectifier Fed DC Drives Problems Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives20 12-pulse converter – consists of two 6-pulse controlled rectifiers connected in parallel

21
Rectifier Fed DC Drives Problems 2. Low supply power factor Power factor related to firing angle of rectifier Low power factor especially during low speed operations Solution: Employ pulse-width modulated (PWM) rectifiers using GTOs, IGBTs High power factor Low harmonic supply currents Low efficiency - high switching losses (disadvantage) Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives21

22
Rectifier Fed DC Drives Problems 3. Effect on motor Ripple in motor current – harmonics present (most dominant is 6 th harmonic) causes torque ripple, heating and derating of motor solution: extra inductance added in series with L a Slow response Discontinuous current may occur if L a not large enough Motor is lightly loaded Effect of discontinuous current Rectifier output voltage increases motor speed increases (poor speed regulation under open-loop operation) Dr. Ungku Anisa, July 2008EEEB443 - Control & Drives22

23
References Rashid, M.H, Power Electronics: Circuit, Devices and Applictions, 3 rd ed., Pearson, New-Jersey, 2004. Dubey, G.K., Fundamentals of Electric Drives, 2 nd ed., Alpha Science Int. Ltd., UK, 2001. Krishnan, R., Electric Motor Drives: Modeling, Analysis and Control, Prentice-Hall, New Jersey, 2001. Nik Idris, N. R., Short Course Notes on Electrical Drives, UNITEN/UTM, 2008. Ahmad Azli, N., Short Course Notes on Electrical Drives, UNITEN/UTM, 2008. Dr. Ungku Anisa, July 200823EEEB443 - Control & Drives

24
4/13/2015EEL 4242 by Dr. M.H. Rashid24 Three-Phase Full-Converter Figure 10.5 Reference: Rashid, M.H, Power Electronics: Circuit, Devices and Applictions, 3 rd ed., Pearson, New-Jersey, 2004

25
4/13/2015EEL 4242 by Dr. M.H. Rashid25 Waveforms and Conduction Times Figure 10.5 Reference: Rashid, M.H, Power Electronics: Circuit, Devices and Applictions, 3 rd ed., Pearson, New-Jersey, 2004

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google