Review of Power Control Harmonics, Power Factor, … Expo...Review of Power Control Harmonics, Power...

Harmonic Solutions for VFD’s

Review of Power Control Harmonics, Power

Factor, Distortion & Displacement

PQ02 – Power Quality and Monitoring..

PQ03 – Using Test Eqipment to Detect and

Measure PQ Issues

PQ04 – Understanding Power Monitoring

PD02 – Power Quality and Monitoring

MC04 – Installation Considerations for VFD’s

Related Content at the Expo

What Are Harmonics?

Often seen

What Are Harmonics?

What Are Harmonics? What Are

Waveforms?

Rfund.V =...

40.00m

10.00m

20.00m

30.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

• A sinusoidal waveform has no harmonics

What Are Harmonics and Waveforms?

Rtotal.V =...

40.00m

10.00m

20.00m

30.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

• This non-sinusoidal waveform contains harmonics

Let’s Create a Distorted Waveform

Fundamental (1st harmonic) Only

• fundamental at 60Hz

Fundamental and 5th Harmonic

• Some 5th harmonic , 153deg

1st, 5th and 7th Harmonics

•A little of 7th harmonic , 282deg

1st, 5th, 7th and 11th Harmonics

•A bit of 11th harmonic , 0deg

1st and Sum of the 5th, 7th and

• Sum the 5th, 7th and 11th harmonic currents

Fundamental, Harmonics, Total

• Sum the harmonics with the fundamental

FFT and How Are Harmonics

Measured?

Power Source

AC Drive

Motor M

Harmonic

Power Meter

Performing FFT

A1 Waveform178.67 Arms, 34.40 %THD

1 5 10 15 20 25 30 35 40 45 5010/28/2010 - 1:46:18.297 PM

FFT, RSS, THD

Harmonic

Number

Frequency

Amplitude

0 DC 0.00 0.00 0

1 60 70.71 5000.00 357

3 180 0.00 0.00 0

5 300 27.97 782.50 153

7 420 10.85 117.67 282

9 540 0.00 0.00 0

11 660 5.54 30.74 0

13 780 2.79 7.79 81

15 900 0.00 0.00 0

17 1020 2.54 6.44 189

19 1140 1.45 2.09 246

21 1260 0.00 0.00 0

23 1380 1.37 1.88 10

25 1500 0.91 0.84 58

27 1620 0.00 0.00 0

29 1740 0.78 0.61 185

Sum of 3rd to 29th 950.56

Square Root of Sum 30.83 Iharm

Sum of 1st to 29th 5950.56

Square Root of Sum 77.14 Itotal

Iharm = 30.83A

Ifund = 70.71A

Itotal = 77.14A

ITHD = 43.6%

= Iharm / Ifund

What Is I(THD)?

ITHD = Iharm / Ifund

So, Iharm = ITHD * Ifund

•ITHD is a ratio between two numbers, it does not stand alone!

We can decrease ITHD

by either decreasing Iharm or increasing Ifund

Frequency, Amplitude, Phase Angle

•Harmonics are simply integer multiples of the fundamental frequency

– for example, if 60Hz is the fundamental (sometimes referred to as the 1st harmonic), then the 2nd harmonic is 120Hz, the 3rd harmonic is 180Hz, etc.

•Any non-sinusoidal waveform can be created by the addition of harmonics at various amplitudes and phase angles

Electrical Loads and Current Harmonics

Power Source Load Type ?

Line Current Harmonics?

What are Loads That Do Not Have

Current Harmonics?

• This is an example of a linear load

Voltage Current

What are Loads That Do Not Have

Current Harmonics?

• This is an example of a linear load

Voltage

Current

Examples of Linear Loads

Induction motors

Incandescent lights

Resistance heaters

Power Factor Correction Caps

Electromagnetic devices

Transformers

non-linear

• During energization

• Over-voltage

What are Loads That Have Current

Harmonics?

Rfund.V =...

Rtotal.V =...

40.00m

10.00m

20.00m

30.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

• This is an example of a non - linear load

• A non-sinusoidal waveform contains harmonics

Examples of Non-Linear Loads

Single Phase

Fluorescent lights (ballast)

Incandescent lights with light dimmers

Anything with an ac-dc power supply

Computers (ac-dc PS)

Monitors (ac-dc PS)

TVs (ac-dc PS)

LED lighting

Three Phase

Welders

Arc furnaces

DC power supplies

DC Drives

Phase control

AC Drives

6-Step

A Typical AC Drive

Power Source AC Drive Motor

Line Current Harmonics

How Do Drives Create Harmonics?

What Does it Do?

Converter

AC to DC

Inverter

DC to AC

Filter

AC Drive

r Outp

Input Output

480Vac

0-460Vac

0-60Hz

650Vdc

Bus = Fixed Vdc

Let’s Look at Some Voltages and

Current

LoadVab

First Current Pulse

Into A

Out of B

Second Current Pulse

Into A

Out of C

Typical Current Waveform for 6

Diode (Pulse)

Rtotal.V =...

40.00m

10.00m

20.00m

30.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

Spectrum – 3ph Diode Bridge

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic Number

litude

1 3 5 7 9 11 13 15 17 19 21 23 25

Why do the line currents

contain 5th and 7th

harmonics?

Harmonic Number

Why 5th and 7th?

Harmonics

20 NOTE: No even harmonics because each half cycle is identical

Rfund.V =...

Rtotal.V =...

40.00m

10.00m

20.00m

30.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

Harmonics

NOTE: No triplens (multiples of 3)

SO WHAT……what do I care

if adjustable speed drives

draw current harmonics

on a power distribution

system?

Issues with Excessive Harmonic Current

Current Harmonics

create

Voltage Distortion

HARMONIC SOURCE

EQUIPMENT

TELEPHONE

EQUIPMENT

PROCESSING

CENTER

Summary of Excessive Harmonic Current Concerns

• Increased Utility current requirement – Inability to expand or utilize

equipment

– Larger wire size needed = increased installation costs

• Component overheating – Distribution transformers,

generators & wires

• Reduced Utility power factor – Increase in utility costs

• Equipment malfunction – Due to voltage distortion with

multiple or loss of zero crossing

– Due to voltage distortion such as flat topping

• Excitation of Power System Resonance's creating over-voltage’s – If PFCC in system

HARMONIC SOURCE

EQUIPMENT

TELEPHONE

EQUIPMENT

PROCESSING

CENTER

PFC PFC

When Should You Be Concerned

About Harmonics?

If service Transformer is Loaded near rating 60%

20 % of total Load is Non-Linear electronic load

When PF correction capacitors Used or Planned

When Voltage Distortion exceeds 8%

Example of High Ithd with Low Vthd - 1500kVA, 75hp

Ithd = 37% Vthd = 0.9%

Example of High Ithd with High Vthd - 75kVA, 75hp

Ithd = 29% Vthd = 9.3%

Excessive Harmonic Current

Causing Voltage Flat-Topping

Excessive Harmonic Current

Causing Voltages with High Peaks

Event #397 at 12/23/2009 22:19:59.800

Ev ent Details/Waveforms

22:19:59.86

12/23/2009

Wednesday

22:19:59.87 22:19:59.88 22:19:59.89

D V A-B V B-C V C-A V

477VAC RMS

720 volts peak

IEEE Std 519-2014

* Provides harmonic current limits for a facility * Provides harmonic voltage limits for the utility connected to facility

What Are the IEEE 519-2014

Standards?

Application Maximum THD (%)

Special Applications - hospitals and airports 3.0%

General System 5.0%

Dedicated System - exclusively converter load 10.0%

Harmonic Voltage LimitsLow-Voltage Systems

Table 10.2

Application Max Notch Depth

Special Applications - hospitals and airports 10%

General System 20%

Dedicated System - exclusively converter load 50%

Harmonic Voltage Limits

Low-Voltage Systems

Rule of Thumb –

Keep notch depth less than 10% if any other equipment will

be connected to that same point of common coupling.

Standards?

Table 10.2

Application Max Notch Depth

Special Applications - hospitals and airports 10%

General System 20%

Dedicated System - exclusively converter load 50%

Harmonic Voltage Limits

Low-Voltage Systems

Standards?

Table 10.3

Current distortion Limits for General Distribution Systems (120V through 69,000V)

Isc/Iload <11 11<=h<17 17<=h<23 23<=h<35 35<=h TDD (%)

<20 4.0 2.0 1.5 0.6 0.3 5.0

20<50 7.0 3.5 2.5 1.0 0.5 8.0

50<100 10.0 4.5 4.0 1.5 0.7 12.0

100<1000 12.0 5.5 5.0 2.0 1.0 15.0

>1000 15.0 7.0 6.0 2.5 1.4 20.0

Even harmonics are limited to 25% of the odd harmonic limits above

Isc=maximum short circuit current at PCC

Iload=maximum demand load current (fundamental frequency component) at PCC

Maximum Harmonic Current Distortion in Percent of Iload

Table 10.3

Current harmonics create voltage harmonics so there are current harmonic limits

What Is Ithd vs Itdd?

Ithd = Iharm / Ifund at any speed or load level

Itdd (IEEE519) = Iharm / Ifund at max load

Itdd (xfmr) = Iharm / Ifund at rated transformer current

6-Pulse Buffered Drive Currents

0 20 40 60 80 100 % Load

ent, a

How Does Motor Load Affect ITHD?

Ifund decreases as load decreases

Iharm decreases as load decreases

(drive is at full speed)

NOTES:

ITHD = Iharm / Ifund

ITHD increases as load decreases

Vthd vs Load

0 10 20 30 40 50 60 70 80 90 100

% Load

Ithd, %

Iharm, A

Vthd, %

100hp drive on 250kVA xfmr, 6%

Why Itdd on Table 10.3?

Itdd is called for because that is a worst case

condition.

Please note:

This is not where Ithd is maximum

But, it is where Vthd is maximum because Iharm is

maximum

When Vthd is a maximum, then greatest likelihood of

problems exist

The Goal of IEEE 519

Thou Shalt Not

Mess Up

Neighbor’s

Line Voltage

Shalt Not

Mess Up

Neighbor’s

Line Voltage

Who Is Your Neighbor?

transformertransformer

2500kVA

5.75%Z

480Vsec

utility

2500kVA

5.75%Z

480Vsec

utility

Customer

Iharm A

Iharm B

Iharm C

Ifund A

Ifund B

Ifund C

I(TDD) is measured at each metering point

Goal is to

keep the V(THD) at

PCC1 <= 5%,

Example

transformertransformer

2500kVA

5.75%Z

480Vsec

utility

2500kVA

5.75%Z

480Vsec

utility

Customer

113Arms

101Arms

72Arms

981Arms

926Arms

1053Arms

241Arms

2960Arms

I(TDD) limits are met at each metering point

at PCC1:

V(THD) = 3.6%

300hp 6-p drives

600hp linear load

80hp unbuf drives

700kW linear load

1000hp 12-p drives

What About Within Customer A or B

113Arms

981Arms

Meets IEEE 519 at PCC1 and within plant

Isc/Iload = 53.3

V(THD) = 2.0%

I(TDD) = 11.5%

V(THD) <= 10%

Customer A

V(THD) <= 8%

300hp 6-P drives

600hp linear loads

V(THD) <= 8%

What About Back-up Generator?

Meets IEEE 519 within the plant if the generator is sized properly

Isc/Iload = 53.3

V(THD) = 2.0%

I(TDD) = 11.5%

V(THD) <= 10%

Customer A

V(THD) <=8%

300hp 6-P drives

600hp linear loads

G V(THD) <8%

Information Needed for Generator

Applications

Generator Issue Information Required

kW Rating Prime Mover / Engine Specifications Generator Reactive Capability Curve

kVAR Lagging Generator Reactive Capability Curve

kVAR Leading Generator Reactive Capability Curve

Voltage Distortion Generator Impedance, Xd”

Voltage Notching Generator Impedance, Xd”

Harmonic Current Regulator Control

Drive Precharge Regulator Control

Table 3 – Generator Issues and Information Required to Understand and Resolve those Issues.

General Guidelines For 6 pulse drives Generator sized 250% of Drive HP

For 18 pulse drives Generator sized 125% of Drive HP

HARMONIC

Current

Ireact

Itotal

(in phase with

line-to-neutral

voltage, VLN)

REACTIVE

Current

x-axis

y-axis

z-axis

Current

222 DQPS

What is the Power Factor

Non-Linear load?

Linear Load Power Factor Non-Linear Load Power Factor

No Current Distortion Includes the Effect of Current Distortion

PF = Watts/VA

or phase angle between

voltage and current

What About the Power Factor?

Power Factor

Displacement power factor - PF(disp) PF(disp) = Ireal / Ifund = a number between .01 and 1.0

involves only the fundamental quantities

includes the real and reactive currents

Distortion power factor - PF(dist) PF(dist) = Ifund / Itotal = a number between .01 and 1.0

includes the fundamental and harmonic (distorted) currents

Itotal = fundamental and harmonic currents

Total PF = PF(disp) * PF(dist)

Current Amplitudes

• Itotal = 105.6Arms • Iharm = 33.1Arms

• I5 = 29.3Arms

• I7 = 10.9Arms

• I11 = 7.9Arms

• I13 = 4.5Arms

• ……. • Ifund = 100.3Arms

• Ireal = 98.6Arms

• Ireact = 18.0Arms

Current Amplitudes

• Itotal = 105.6 Arms

• Iharm = 33.1 Arms

• Ifund = 100.3 Arms

• Ireal = 98.6 Arms

• Ireact = 18.0 Arms

Current Relationships

Itotal = 105.6Arms

• Iharm = 33.1Arms

• Ifund = 100.3Arms

Ireal = 98.6Arms

Ireact = 18.0Arms

PFdisp = Ireal/Ifund = 0.98

PFdist = Ifund/Itotal = 0.95

PFtotal = PFdisp*PFdist

PFtotal = 0.93

How can we reduce

(mitigate) the

harmonic current?

Drive Without DC Link Choke

• Typical ITHD

of 80 to

• Sensitive to

line voltage

transients

• High peak

line currents

La.I = f( ...

150.0m

200.0m

162.5m

175.0m

187.5m

-400.0 -400.0

-200.0 -200.0

200.0 200.0

Transformer

Common

configuration for

drives < 5hp

NOTE: Ipk about 3x Irms

Line Reactor, Drive w/o DC Link Choke

• Typical ITHD

of 30 to 45%

• Big help for

drives

without DC

link choke

La.I = f(t...

150.0m

200.0m

162.5m

175.0m

187.5m

-400.0 -400.0

-200.0 -200.0

200.0 200.0

Transformer

Line Reactor

Typical values are 3% and

5% impedance

NOTE: shown is 3% LR

Drive With DC Link Choke

• Typical ITHD of

30 to 40%

• Less sensitive

to line transients

La.I = f(t...

150.0m

200.0m

162.5m

175.0m

187.5m

-400.0 -400.0

-200.0 -200.0

200.0 200.0

NOTE: Ipk about 1.5x Irms

Transformer

DC Link

Line Reactor in Addition to a DC Link

• Typical ITHD of

20 to 35%

• Big help for

drives w/o DC

link choke

• 0.75 - 0.95 PF

La.I = f(t...

150.0m

200.0m

162.5m

175.0m

187.5m

-400.0 -400.0

-200.0 -200.0

200.0 200.0

Transformer

Line Reactor

DC Link

Typical values are 3%

and 5% impedance

NOTE: shown is 3% LR

Passive Harmonic Filter

• Typical ITHD of

4 to 7%

• 0.3 to 1.0 PF

Ia = f( S,...

-25.00m

24.90m

-20.00m

-10.00m

10.00m

20.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

Transformer

Passive Filter

DC Link

Active Harmonic Filter

• Typical ITHD of 3

• 0.9 - 0.99 PF

Ia = f( S,...

-25.00m

24.90m

-20.00m

-10.00m

10.00m

20.00m

-150.0 -150.0

-100.0 -100.0

-50.0 -50.0

50.0 50.0

100.0 100.0

Transformer

DC Link

Chokexfmr

% Z AC

Ifund Ifund + Iharm

Active Filter

Current from Transformer

Multi-Pulse VFD

• 12-Pulse

Typical ITHD of

9 to 12%

• 18-Pulse

Typical ITHD of

4 to 5%

• 0.90 - 0.99

Ia = f( S,...

-25.00m

24.90m

-20.00m

-10.00m

10.00m

20.00m

-200.0 -200.0

-100.0 -100.0

100.0 100.0

Transformer

Multi-Phase

Transformer

DC Link

Multi-Set

6 pulse bridge

Spectrum – 3ph Diode Bridge

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic Number

litude

Spectrum – 12 Pulse Diode Bridge

Harmonic Number

litude

1 3 5 7 9 11 13 15 17 19 21 23 25

Spectrum – 18 Pulse Diode Bridge

Harmonic Number

litude

1 3 5 7 9 11 13 15 17 19 21 23 25

Active Front-End

• Typical ITHD of 3

• Regen

• 0.8 – 1.0 PF

Lx1.I = ...

145.0m

195.0m

150.0m

162.5m

175.0m

187.5m

-200.0 -200.0

-100.0 -100.0

100.0 100.0

Transformer

Notch Filter

Popular Harmonic Mitigation

Choices

• 18-Pulse - widely accepted – Works well – Has become more expensive

• Passive Filters – Suited to lower power ratings <100 hp – Numerous suppliers

• Active Filters – Versatile – used for single drives or multiple drives

• AFE – Increasing in interest and use – Feature of line regeneration capability makes it

attractive

What Did We Learn?

• What are harmonics? – Distorted waveform, sine

wave element that make up distorted waveform

• How are they measured? – FFT RSS THD TDD PCC

• Why do drives produce line current harmonics?

– Non Linear Load, 6 pulse rectifiers

• How much is too much?

– Voltage distortion greater than 5%

• How do we apply IEEE-519?

– Limits guidelines

• How do harmonics vary with load?

– Voltage distortion increase as Iharm increases as a % of maximum available current

• How can the drive harmonics be reduced?

– DC link choke, Line reactor, Passive filter, active filter, xfmr config, multipulse converter, active front end

• What about Power Factor?

– Disp pf high, total pf is dist pf * disp pf ( lower than disp pf)

• Total pf proportional to Ithd

– Be careful with passive filters and leading pf

• What about gensets ( Generators )?

– Increase in Vthd due to greater impedances,

– Voltage regulation issues when applied to drives

HARMONIC SOURCE

EQUIPMENT

TELEPHONE

EQUIPMENT

PROCESSING

CENTER

PQ02 – Power Quality and Monitoring..

PQ03 – Using Test Eqipment to Detect and Measure PQ Issues

PQ04 – Understanding Power Monitoring

PD02 – Power Quality and Monitoring

MC04 – Installation Considerations for VFD’s

You can find these products in the

Solution Area SA01

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