Download presentation

Presentation is loading. Please wait.

Published byAlbert Luxon Modified about 1 year ago

1
© ABB Month DD, YYYY | Slide 1 ASHRAE Rocky Mountain Chapter VFD Fundamentals April 16, 2010 Jeff Miller - ABB 2010

2
What is a Drive / VFD/ AFD? Volts Hertz V 60 Hz = 7.67 V Hz 230 V 60 Hz = 3.83 V Hz If 230 VAC Power Line: 230 V Motor 460 V Motor

3
What is a Drive? Motor L1 L2 L3 C L Input Converter (Diode Bridge) Output Inverter (IGBT’s) DC Bus (Filter) + _ + _ + _ + _ ++ __

4
What is a Drive?

5
A variable frequency drive converts incoming 60 Hz utility power into DC, then converts to a simulated variable voltage, variable frequency output VFD Fundamentals 60 Hz Power Electrical Energy ABB Zero Hz To Motor VFD RECTIFIER (AC - DC) INVERTER (DC - AC) ACDCAC VFD Zero Hz 60 Hz

6
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

7
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

8
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

9
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

10
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

11
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

12
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

13
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

14
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

15
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

16
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

17
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

18
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

19
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

20
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

21
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

22
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

23
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

24
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

25
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

26
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

27
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

28
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

29
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

30
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

31
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

32
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

33
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

34
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER

35
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Area Under The Square-Wave Pulses Approximates The Area Under A Sine Wave Frequency Voltage

36

37
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER How Often You Switch From Positive Pulses To Negative Pulses Determines The Frequency Of The Waveform Frequency Voltage

38
Frequency = 30Hz Frequency = 60Hz

39
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

40
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

41
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

42
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

43
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

44
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

45
RECTIFIER Positive DC Bus Negative DC Bus + - INVERTER Motor

46
Non-Linear Loads? Loads which draw non-sinusoidal current from the line: –Non-incandescent lighting –Computers –Uninterruptible power supplies –Telecommunications equipment –Copy machines –Battery chargers –Electronic variable speed drives –Any load with a solid state AC to DC power converter

47
Typical AC Drive Configuration M 460VAC 3-phase 650VDC Simulated AC (PWM) All AC Drives rectify AC to DC, then convert to simulated AC (PWM) to provide the motor Variable voltage and Frequency. The AC to DC conversion generates harmonics.

48
Harmonics — Definitions Non-linear loads draw current in a non-sinusoidal or distorted manner Harmonics or harmonic content is a mathematical concept implemented to allow quantification and simplified analysis of non-linear waveforms Harmonics are typically present in both network currents and network voltages Non-linear current draw creates non-linear voltage as it flows through the electrical network –Current harmonics Voltage harmonics

49
Harmonic Frequencies Fundamental 5th Harmonic 7th harmonic 11th Harmonic 13th Harmonic 17th Harmonic 19th Harmonic 60 Hz 300 Hz 420 Hz 660 Hz 780 Hz 1020 Hz 1140 Hz

50
The Theory: Fundamental, 5 th and 7 th Harmonics Fundamental 5th 7th Components Summation

51
Harmonic Content, 6- Pulse Drive PWM Drive Harmonic Input Spectrum 5th 7th Fundamental 11th 13th

52
–Harmonic Current Distortion — Added heating in transformers and cables, reduces available capacity May stimulate a resonance condition with Power Factor Correction Capacitors –Excessive voltage –Overheating of PF correction capacitors –Tripping of PF protection equipment Voltage Distortion interfering w/ sensitive equipment. Largest Concern! Harmonics — Why worry?

53
Harmonics, Important Terminology (Definitions per IEEE ) Harmonic - A sinusoidal component of a periodic wave or quantity having a frequency that is an integral multiple of the fundamental frequency. Point of common coupling (PCC) Def. 1 - “point of common coupling (PCC) with the consumer-utility interface.” (current harmonic emphasis) This is typically the primary of the main transformer(s). This is to protect the utility. – Secondary of transformer for Voltage Distortion. This is to protect the USER.

54
PCC Example

55
Harmonics, Important Terminology (cont.) I SC /I L - The ratio of the short-circuit current available at the point of common coupling, to the maximum fundamental load current. Total harmonic distortion (THD) or distortion factor - The ratio of the root-mean-square of the harmonic content to the root-mean-square value of the fundamental quantity, expressed as a percent of the fundamental. Total demand distortion (TDD) - The root-sum-square harmonic current distortion, in percent of the maximum demand load current (15 or 30 min demand).

56
Effect of Short Circuit Ratio on Harmonics I SC I L ~ 400 I SC I L ~ 8

57
–Harmonics produced by an individual load are only important to the extent that they represent a significant portion of the total connected load –Linear loads help reduce system harmonic levels –TDD equals the THD of the nonlinear load multiplied by the ratio of nonlinear load to the demand load: Harmonics — A System Issue! Where TDD=TDD of the system THD NL =THD of the nonlinear loads NL=kVA of nonlinear load DL=kVA of demand load (nonlinear + linear)

58
Harmonics — By the Numbers IEEE

59
Harmonics — By the Numbers (cont.) IEEE

60
Harmonics — Attenuation Options Reactors (Chokes) Passive Filters –Harmonic Trap –Hybrid High Pulse Count Rectification Active Filters –Drive Front End –Stand Alone

61
Reactors (Chokes) Simplest and least expensive harmonic reduction technique May be included in base drive package Often meet harmonic needs provided drive load is a small portion of total connected load May be implemented with AC line reactors or with DC link reactors –AC line reactors provide better input protection –DC link reactors provide load insensitive drive output voltage –Both types provide similar harmonic benefits “Swinging” choke design provides enhanced light load harmonic performance

62
Reactors, AC Line or DC Link Different design techniques Equal harmonic reduction for same normalized % reactance Typical full load THD (current) at drive input terminals 28% 46%

63
Hybrid Filter Installs in series with drive input May feed multiple drives Improves power factor (may go leading) Typical full load THD (current) at filter input terminals 5% 8% Relatively unaffected by line imbalance

64
High Pulse Count Rectification Typical configurations are either 12 pulse or 18 pulse Phase shifting transformer is required Additional drive input bridge(s) is needed Typical full load THD (current) at transformer primary 8% 12% (12 pulse), 4% 6% (18 pulse) Performance severely reduced by line imbalance (voltage or phase) Excellent choice if step-down transformer is already required

65
High Pulse Count Rectification (cont.) 6 pulse rectifier Transformer and cabling simple Current very distorted I thd typically 45% with 3% reactor DC/AC Transformer and cabling complicated Current distorted I thd 8% to 12% (depending on network impedance) 12 pulse rectifier 18 pulse rectifier DC/AC Transformer and cabling complicated Current wave form good I thd 4% to 6% (depending on network impedance)

66
Active Filter Front End with LCL Filter LCL Filter (Sine Filter) removes high frequencies >1 kHz. (Current and voltage) Full output voltage is available with 80% input voltage (400V In = 480V Out ) Full regenerative capability No transformer required Not affected by line imbalance LCL filter Line inverter (rectifier) Motor inverter Motor LL C M

67
Remember! Even an 80% THD nonlinear load with a will result in only 8% TDD if the nonlinear load is 10% and the linear load is 90%. (80%(10%/(10%+90%))=8%) Harmonic Reduction Summary

68
Summary – Practical Advice With a main distribution transformer, 20-30% of its load on non-linear loads will typically comply with IEEE Voltage distortion causes interference with sensitive equipment, not current distortion! 5% reactors address 90+% of typical applications. They also provide protection against line transients and keep input currents low to avoid oversizing power wiring to comply with NEC. Make VFD vendor perform a harmonic distortion calculation with the submittals.

69
PEAK: 1,040 volts

70
Peak Voltage all at 50’ of cable Peak Voltage has many Contributing Factors Inverter Rated Motors Help Minimize the Issue Less dV/dT minimizes; problems with RFI/EMI Motor Insulation & Bearing Current DrivePeak Voltage

71
Recommendations Keep cable length short as possible Use a NEMA MG1, Part 31 motor (not “inverter duty” or “inverter ready” Ensure that grounding is sound

72

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google