We've updated our privacy policy. Click here to review the details. Tap here to review the details.

Successfully reported this slideshow.

Your SlideShare is downloading.
×

Activate your 30 day free trial to unlock unlimited reading.

Activate your 30 day free trial to continue reading.

Top clipped slide

1 of 30
Ad

Download to read offline

Lecture PPT

Lecture PPT

- 1. Direct Current Motor Drives:
- 2. DC DRIVES Vs AC DRIVES DC drives: Advantage in control unit Disadvantage in motor AC Drives: Advantage in motor Disadvantage in control unit
- 3. • DC DRIVES: Electric drives that use DC motors as the prime movers • Dominates variable speed applications before PE converters were introduced • DC motor: industry workhorse for decades • Will AC drive replaces DC drive ? – Predicted 30 years ago – AC will eventually replace DC – at a slow rate – DC strong presence – easy control – huge numbers DC DRIVES
- 4. DC Motors • Limitations: • Advantage: simple torque and speed control without sophisticated electronics • Regular Maintenance • Expensive motor • Heavy motor • Sparking
- 5. General Torque Equation Translational (linear) motion: dt d J T Rotational motion: dt dv M F F : Force (Nm) M : Mass (Kg ) v : velocity (m/s) T : Torque (Nm) J : Moment of Inertia (Kgm2 ) : angular velocity ( rad/s )
- 6. Torque Equation: Motor drives dt d J T T or dt d J T T L e L e 0 L e T T Acceleration 0 L e T T Deceleration 0 L e T T Constant speed Te : motor torque (Nm) TL : Load torque (Nm)
- 7. …continue Drive accelerates or decelerates depending on whether Te is greater or less than TL During acceleration, motor must supply not only the load torque but also dynamic torque, ( Jd/dt ). During deceleration, the dynamic torque, ( Jd/dt ), has a negative sign. Therefore, it assists the motor torque, Te.
- 8. Torque Equation: Graphical Te Forward running Speed Forward braking Reverse acc. Reverse running Reverse braking Forward acc.
- 9. Load Torque Load torque, TL, is complex, depending on applications. SPEED TORQUE TL = k2 TL = k TL = k In general:
- 10. 4Q OPERATION SPEED TORQUE I III II IV Te Te Te Te FM FB RM RB F: FORWARD R: REVERSE M : MOTORING B: BRAKING
- 11. 4Q OPERATION: LIFT SYSTEM Counterweight Cage Motor Positive speed Negative torque
- 12. 4Q OPERATION: LIFT SYSTEM Convention: Upward motion of the cage: Positive speed Weight of the empty cage < Counterweight Weight of the full-loaded cage > Counterweight Principle: What causes the motion? Motor : motoring P =T = +ve Load (counterweight) : braking P =T = -ve
- 13. You are at 10th floor, calling fully-loaded cage from gnd floor You are at gnd floor, calling empty cage from 10th floor You are at 10th floor, calling empty cage from gnd floor You are at gnd floor, calling Fully-loaded cage from 10th floor Torque Speed FM FB RM RB
- 14. DC MOTOR DRIVES Principle of operation Torque-speed characteristic Methods of speed control Armature voltage control Variable voltage source Phase-controlled Rectifier Switch-mode converter (Chopper) 1Q-Converter 2Q-Converter 4Q-Converter
- 15. Current in Current out Stator: field windings Rotor: armature windings Principle of Operation DC Motors
- 16. Equivalent circuit of DC motor a t i k Te Electromagnetic torque E a k e Armature back e.m.f. Lf Rf if a a a a t e dt di L i R v + ea _ La Ra ia + Vt _ + Vf _ dt di L i R v f f f f
- 17. Torque-speed characteristics a a a a E I R V In steady state, T a e T a k V T k R 2 Therefore speed is given by, Three possible methods of speed control: Armature resistance Ra Field flux F Armature voltage Va a a a a a e dt di L i R V Armature circuit:
- 18. Torque-speed characteristics of DC motor Torque Speed Maximum load Torque No load speed Separately excited DC motors have good speed regulation. Full load speed
- 19. DC Motor Speed Control Torque Speed Maximum Torque By Changing Ra Ra increasing • Power loss in Ra • Does not maintain maximum torque capability • Poor speed regulation
- 20. DC Motor Speed Control Torque Speed Maximum Torque Flux Decreasing Trated • Slow transient response • Does not maintain maximum torque capability By Decreasing Flux
- 21. DC Motor Speed Control Torque Speed Maximum Torque By Changing Armature voltage Trated Va increasing • good speed regulation • maintain maximum torque capability
- 22. Speed control of DC Motors Below base speed: Armature voltage control (retain maximum torque capability) Above base speed: Field weakening (i.e. flux reduced) (Trading-off torque capability for speed) Torque speed Line of Maximum Torque Limitation Armature voltage control Field flux control base
- 23. Methods of Armature Voltage Control Phase-controlled rectifier (AC–DC) T Q1 Q2 Q3 Q4 3-phase Or 1-phase supply + Vt ia
- 24. Methods of Armature Voltage Control 1. Ward-Leonard Scheme 2. Phase-controlled rectifier (AC–DC) 3. Switch-Mode Converter (Chopper) (DC–DC)
- 25. Phase-controlled rectifier: 4Q Operation Q1 Q2 Q3 Q4 T 1 or 3- phase supply 1 or 3- phase supply + Vt Methods of Armature Voltage Control
- 26. Phase-controlled rectifier : 4Q Operation Q1 Q2 Q3 Q4 T F1 F2 R1 R2 + Va - 3-phase supply AN ALTERNATIVE WAY
- 27. Switch–mode converters: 1Q Converter Q1 Q2 Q3 Q4 T + Vt - T1 Converters For DC motor Drives
- 28. Switch–mode converters: 2Q Converter + Vt - T1 D1 T2 D2 Q1 Q2 Q3 Q4 T Q1 T1 and D2 Q2 D1 and T2 Converters For DC motor Drives
- 29. Switch–mode converters: 4Q Converter Q1 Q2 Q3 Q4 T + Vt - T1 D1 T2 D2 D3 D4 T3 T4 Converters For DC motor Drives
- 30. Switch–mode converters • Switching at high frequency Reduces current ripple Increases control bandwidth • Suitable for high performance applications Advantages of Switch mode converters

No public clipboards found for this slide

You just clipped your first slide!

Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips.Hate ads?

Enjoy access to millions of presentations, documents, ebooks, audiobooks, magazines, and more **ad-free.**

The SlideShare family just got bigger. Enjoy access to millions of ebooks, audiobooks, magazines, and more from Scribd.

Cancel anytime.
Be the first to like this

Total views

2

On SlideShare

0

From Embeds

0

Number of Embeds

1

Unlimited Reading

Learn faster and smarter from top experts

Unlimited Downloading

Download to take your learnings offline and on the go

You also get free access to Scribd!

Instant access to millions of ebooks, audiobooks, magazines, podcasts and more.

Read and listen offline with any device.

Free access to premium services like Tuneln, Mubi and more.

We’ve updated our privacy policy so that we are compliant with changing global privacy regulations and to provide you with insight into the limited ways in which we use your data.

You can read the details below. By accepting, you agree to the updated privacy policy.

Thank you!

We've encountered a problem, please try again.