01. ELECTROMAGNETIC COMPATIBILITY (EMC)

TECHNICAL SEMINAR - 2 nd PART - EMC & THD

POWER ELECTRONICS R&D

20 th February2011

Index

01

Electromagnetic Compatibility (EMC)

02

Total Harmonic Distortion (THD)

Index

01

Electromagnetic Compatibility (EMC)

02 Total Harmonic Distortion (THD)

01.

ELECTROMAGNETIC COMPATIBILITY (EMC)

Index

> INTRODUCTION

> CONDUCTED NOISE

> INPUT

- RFI- EMC Input filter

> OUTPUT

- Common Mode Ferrites

- dV/dt Filter

- Sinusoidal/ LC Filter

> COMPETITORS

> STANDARDS & REGULATIONS

> Directiva OMC 2004/108/CE

> IEC/EN 61800-3

> IEEE 519-1992

01.


Introduction

EMC

Electromagnetic Compatibility

EMI

Electromagnetic Interference

EMS

Electromagnetic Susceptibility

COMPATIBILITY MARGIN

Device Immunity level

Minimum Immunity level

Maximum Emission level

Device emission level

Frequency spectrum

01.


Introduction

EMC

Electromagnetic Compatibility

Low frequency

F Z> 150 kHz

 THD

 Flicker

EMI

Electromagnetic Interference

Medium

Frequency

150 kHz< f < 30MHz

 Conduced

High

Frequency f < 30MHz

 Radiated

EMS

Electromagnetic Susceptibility

 Radio Frequency

 Conduced

 Radiated

 Surges

 Electrical fast transients

 Electrostatic discharges

 THD

 Voltage dips and interruptions

IEEE 519-1992 IEC61800-3 EMC 2004/108/CE

01.


OMC | Radiated & Conduced

The electric noise is produced by the inverter bridge. It is due to the interruption of the current signal when the thyristors commutate their status (switch over ON and OFF and vice versa).

For this reason the electric noise is a high frequency current signal which is coupled to the current that is flowing in the drive to the motor and that additionally can be emitted.

It is necessary to deal with two kind of emissions:

01.


OMC | Radiated

The RADIATED electric noise will be attenuated considering:

 The use of metallic conductions.

 The use of shielded wires.

 The own metallic cabinet of the drive will help to minimize this effect.

01.


Index

> INTRODUCTION


> INPUT


> OUTPUT


- dV/dt Filter


> COMPETITORS



> IEC/EN 61800-3

> IEEE 519-1992

01.


OMC | Conduced | Input

Noise coupled to the INPUT SIGNAL of the drive



Recommended use of RFI Input Filters (Radio Frequency Interferences) as well called

EMC Filters (Electro-Magnetic Compatibility).



Regulation which controls the selection of these filters is UNE-EN 61800-3/A11:2002 .

See details on Annex I.

01.


OMC | Conduced | Output

Noise coupled in the CURRENT FLOWING TO THE MOTOR - OUTPUT

 Output Common Mode Ferrites , in case of the couple noise is common mode noise, that means, noise signal coupled to the capacitances existing between the phases and the earth and also between the motor windings and the earth. This noise is the responsible of the bearing damages.

 dV/dt Output Filters , in case of the coupled noise is differential noise, that means, noise signal coupled to the capacitances existing between phases. This noise will produce isolation drillings and additionally will increase the dV/dt factor. These filters can be:

 Output Inductance (output coils in series, one per phase)

 Iron Dust Toroids , in all output phases.

 Sinusoidal / LC filters , deals with the problem by converting the chopped signal into a sinusoidal signal reducing the noise.

01.


OMC | Conduced | Output

It is possible to observe that the output waveform of the drive is as follow:

This is the result of the inverter bridge action.

Show film

01.


OMC | Conduced | Output | dV/dt

If the waveform is amplified, it is possible to observe that the angle is not 90º exactly:

Drive dV/dt Losses

132kW 800V/µs 1380W

132kW 4000V/µs 1100W

01.



By incrementing the dV/dt ramp is possible to reduce the drive losses, that allows to the drives to dissipate less power and consequently they can be smaller.

Drive dV/dt

132kW 800V/µs

Losses

1380W

132kW 4000V/µs 1100W

The main disadvantage of this method is the appearance of brusque over-impulses in the drive output which will be higher at motor input.

It is possible to check this in the measurement realized using a competitor drive:

» Actual measurement on competitor drive of 200A on load

01.



To solve this problem, Power Electronics works over the gate resistor of the IGBTs, guaranteeing that those over-impulses do not overcome a concrete value.

» Actual measurement on a drive of 200A on load: COMPETITOR

Rg is the gate resistor and it controls the load of the “capacitor” which conform the

IGBT.

» Actual measurement on a drive of 200A on load:

POWER ELECTRONICS

01.


OMC | CONDUCED | Output | dV/dt filter

SD700 dV/dt Filter | Iron Dust Toroids

01.



Power Electronics for 690V drives integrates the CLAMP system.

This circuit injects the commutation peak voltage that occurs in the IGBT’s due to the inductance caused by the output cable and the motor.

This system avoids IGBT’s and motor damage and reduce the dv/dt filter overheat.

01.


OMC| CONDUCED | Output | Sinusoidal/LC filter

L

Converts the chopped signal into a sinusoidal signal

C

01.


Index

> INTRODUCTION


> INPUT


> OUTPUT


- dV/dt Filter


> COMPETITORS



> IEC/EN 61800-3

> IEEE 519-1992

01.


OMC| Competitors

SUPPLIER A

For higher cable lengths additional filters must be used. See next pages.

01.


OMC| Competitors

SUPPLIER A

DRIVE

01.


OMC| Competitors

SUPPLIER A

01.


OMC| Competitors

SUPPLIER B

For higher cable lengths additional output chokes must be used. For further details, see next page.

01.


OMC| Competitors

SUPPLIER B

01.


OMC| Competitors

SUPPLIER C

01.


OMC| SD700

SD700 SERIES

 Input chokes (as standard)

 Output dV/dt filters (as standard)

 Electronic control of the dV/dt of the IGBT

 Mechanical construction

 Design of PCB’s

Supply Voltage

Frames

Screened (m)

1 2 3 4

400Vac (-20% to +10%)

5 6 7 8 9 10 11

150 150 150 150 150 150 150 150 150 150 150

Unscreened (m) 300 300 300 300 300 300 300 300 300 300 300

Supply Voltage

Frames

Screened (m)

3

100

4

100

5

550Vac to 690Vac (-20% to +10%)

100

6

100

7

100

8

100

9

100

10

100

11

100

Unscreened (m) 200 200 200 200 200 200 200 200 200

» For higher cable length contact with Power Electronics

01.


OMC| SD700

Admissible Peak voltage limit curves in AC motors terminals:

2.4

2.0

1.6

1.2

0.8

0.4

50m

IEC 60034-25 Curve B

(without filters for motors up to 690V AC)

2.15kV

NEMA MG1 Pt31 in grids of 600V

100m

IEC 60034-25 Curve A

(without filters for motors up to 500V AC)

IEC 60034-17

NEMA MG1 Pt31 in grids of 400V

Effect of the motor range increase

1.86kV

1.56kV

1.35kV

1.24kV

10m

20m

30m

0.1

0.2

Examples of the test results, using reinforced copper wires at 415V rated voltage.

1.1

1.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Rise time of the voltage pulse (µs)

1.0

VFITCC0035AI

01.


OMC| SD700

01.


OMC| SD700

One sample of the tests to the SD700.

01.


OMC| SD700

01.


Index

> INTRODUCTION


> INPUT


> OUTPUT


- dV/dt Filter


> COMPETITORS



> IEC/EN 61800-3

> IEEE 519-1992

01.


Standards & Regulations

The CE certification for Variable

Speed Drive requires compliance with directive

:

EMC 2004/108/CE

IEC61800-3 compliance

IEC61800-3

01.


Standards & Regulations | 61800-3

First environment

Second environment

IEC61800-3/A11

Classifying Criteria

Non restricted distribution

Restricted distribution

Input current  100A

Input current > 100A

Application Limit

C1

C2

C3

C4

WHERE?

First Environment: Includes domestic or residential use. It includes also, places directly connected, without intermediate transformers, to a power supply distribution system of low energy which additionally gives supply to buildings used for domestic uses (cinemas, theatres, shopping centres, hospitals,…).

Second Environment: (Named also industrial). It includes all places different from those which are directly connected to a power supply distribution system of low energy which additionally gives supply to buildings used for domestic uses (factories and facilities supplied with transformer of medium voltage to low voltage).

01.


Standards & Regulations | 61800-3

First environment

Second environment

IEC61800-3/A11

Classifying Criteria

Non restricted distribution

Restricted distribution

Input current  100A

Input current > 100A

Application Limit

C1

C2

C3

C4

WHERE?

Non-Restricted Distribution: Marketing modality where the power supply of the drive does not depend on the customer or user regarding to EMC issues for the application of operation.

Restricted Distribution: Marketing modality where the manufacturer limits the supplying of the drive to those customers or users which, in an independent or together way, have technical competence on the EMC requirements for the application of operation.

01.


Standards & Regulations | 61800-3

C1

1 st Environment

C2

I < 100A

C3

2 nd Environment

I > 100A

C4

EMC PLAN

Quasi pick value Average value

Index

01 Electromagnetic Compatibility (EMC)

02

Total Harmonic Distortion (THD)

02 TOTAL HARMONIC DISTORTION

Index

TOTAL HARMONIC DISTORTION

> Basic principles

> Measurement

> Effects

> Standards & Regulations

> Solutions

- Passive Filters

- FREEMAQ

- Active Filters

- Multipulses drives

> Competitors


Basic Principles | What is the Harmonic Distortion?



It can be demonstrate that any periodic waveform (squared, triangular, …) can be represented as the sum of several sinusoidal waves with different frequencies and phases.



All those waves constitute the harmonic spectrum of the wave.


Basic Principles | What is the Harmonic Distortion?

If g

► 50Hz or 60 Hz If

5rd

► 5 · f g

I

T

= I

1

+ I

5

…..+I n

If

7th

► 7 · f g


Meassurement

Wave Fourier Transform

THDi Value


Meassurement

In variable speed drives applications both the harmonic current distortion and the harmonic voltage distortion are of interest. The harmonic current and voltage distortion have different effects on the power system and it is therefore important to separate them.

The harmonic current distortion is caused by the rectifier part of the variable speed drive, typically a 6-pulse diode rectifier. The harmonic currents can be described as a reactive current adding to the active current. Consequently the harmonic current distortion is increasing the

RMS current and if not taking into account can result in overheating of components such as the supply transformer or cables. The amount of harmonic current distortion is often described in percent of the fundamental current also known as the total harmonic current distortion

(THID).

THID

 h







2

I h

2

I

1


Meassurement

The harmonic current is normally flowing from the harmonic current generator (e.g. the diode rectifier) into the mains. The voltage drop caused by the harmonic currents over the supply impedance causes then the harmonic voltage distortion. I.e. the harmonic voltage distortion is a product of the harmonic current distortion and the supply impedance, where a grid with the largest impedance yields the highest voltage distortion.

The harmonic voltage distortion can interfere with equipment connected to the same line such as direct on-line motors or electronic equipment and eventually cause this equipment to fail. The amount of harmonic voltage distortion is often described in percent of the fundamental voltage also known as the total harmonic voltage distortion (THVD).

THVD

 h







2

U h

2

U

1


Index



> Measurement

> Effects


> Solutions

- Passive Filters

- FREEMAQ

- Active Filters


> Competitors


Effects

 1) Electrical Grid and Power Transformer overload and heating.

 2) Reduction of the Motor Efficiency , non sinusoidal waveforms increases internal heating lost.

 3) Resonance effects and power capacitors banks overload , the power factor corrections systems do not work properly increasing the energy bill.

 4) Electronic and computers underperformance. Low consumption and single phase devices could be affected and do not work properly.


Index



> Measurement

> Effects


> Solutions

- Passive Filters

- FREEMAQ

- Active Filters


> Competitors



The legislation applicable for drives is that described in the international regulation IEC61800-

3. Included in that general regulation, there are some others regulations which refer to harmonics such us IEC61000-2-4 (Class 3: THD=10%) or IEC61000-2-2 (THD=8%)

Literal description extracted from regulation IEC61800-3 :

“The immunity levels used for the design regarding the THD of voltage and the individual harmonics orders will be as minimum equal to the permanent compatibility levels at the IEC61000-2-2 (class 3: THD=10%) or IEC61000-2-4 (THD=8%), for those situations in permanent service.

For transient situations (duration less than 15 seconds), the immunity levels used for the design will be minimum 1.5 times the permanent levels”.



NORMS DESCRIPTION

IEC61000-2-4 The norm establishes the electromagnetic compatibility levels for low frequency conducted distortions at industrial installations.

IEC61000-2-2 The norm establishes the electromagnetic compatibility levels for low frequency distortions at public low voltage supply systems.

IEC61000-2-12 The norm established the electromagnetic compatibility levels for low frequency distortions at public medium voltage supply systems.


Standards & Regulations | IEC61000-2-4

This regulation refers to conducted distortions at frequency ranges from 0kHz to 9kHz. It establishes the numeric values of compatibility levels for industrial supply distribution systems and no publics at nominal voltages up to 35kV and nominal frequencies of 50Hz or 60Hz.

ELECTROMAGNETIC ENVIRONMENT CLASSES

CLASS 1 To protected distribution systems and has compatibility levels lower than the public power supply systems. It is related to the use of the equipments very sensible to the supply distribution distortions, as the electric instruments of technological laboratories, some kind of automatic equipments and protection equipments, some computers, etc

CLASS 2 This class is generally applied to PCC and PCI in industrial supply distribution systems and some others no public supply systems. The compatibility levels are generally identical to the corresponding to public supply systems. For that reason, the equipments (in our case the VSD) designed to be used in public power supply systems could also be used in this class in industrial environment

CLASS 3 This class is applicable only for PCI at industrial environment.

There should be considered under the following conditions: Most par of the load is supplied with converters, there are welding machines, the big motors are often started, the load varies quickly.



Compatibility levels for Total Harmonic Distortions

CLASS 1 CLASS 2 CLASS 3

Total Harmonic Distortion

(THD)

5% 8% 10%

Note: In case of one part of the power supply system is used for important non linear loads, the compatibility levels of class 3 for this par of the supply distribution could be 1,2 times the above mentioned values.

Then it is necessary to take caution for those equipments there connected. Nevertheless, in the CCP (public supply distribution system) the values offered in norms IEC61000-2-2 and IEC61000-2-12 will prevail.



This norm refers to the conducted distortions in the frequency range from 0kHz to 9kHz, with amplified option to 148kHz for signals transmission system to the supply distribution system. These numerical values are offered for compatibility levels in case of public supply distribution system of low voltage with nominal voltage of 420V single-phase or

690V 3-phase and nominal frequency of 50Hz or 60Hz.

Compatibility levels for individual harmonics voltages in low voltage distribution systems.

Odd harmonics not multiple of 3

Order of harmonic

(h)

5

Voltage of harmonic (%)

6

Odd harmonics multiple of 3

(note)


(h)

Voltage of harmonic

(%)

3 5


(h)

2

Even harmonics

Voltage of harmonic (%)

2

7 5 9 1,5 4 1

11

13

17 ≤ h ≤ 49

3,5

3

2,27 x (17/h)-0,27

15

21

21 ≤ h ≤ 45

0,4

0,3

0,2

6

8

10 ≤ h ≤ 50

0,5

0,5

0,25 x (10/h)+0,25

Note: The levels indicated through odd harmonics multiples of three are applied to the homopolar harmonics. So this, in a 3-phase distribution line without neutral cable with no load connected between a phase and ground, the value of the harmonics order 3 and

9 can be lower enough than compatibility levels, depending on the distribution line imbalance.



This norm refers to the conducted distortions in the frequency range from 0kHz to 9kHz, with amplified option to

148,5kHz for signals transmission system to the supply distribution system. These numerical values are offered for compatibility levels in case of public supply distribution system of low voltage with nominal voltage between

1kV and 35kV and nominal frequency of 50Hz or 60Hz.

The compatibility levels are specified for electromagnetic distortion of those types that can be expected in the public power supply distribution systems of medium voltage, with the target of helping to define the following: a) The limits to be established for distortions emissions (in our case of study, harmonics) in the public power supply distribution systems.

b) The immunity limits to be established by products committees or for other devices which support conducted emissions in the public power supply distribution lines.

The medium voltage systems covered by this norm are public power supply distribution systems that supply to: a) Particular installations where devices are connected directly or through transformers.

b) Sub-stations that supply to low voltage public power supply distribution lines.



Compatibility levels for individual harmonic voltages in distribution lines of medium voltage.

Odd harmonic not multiples of 3

Harmonic order (h)

5

7

11

13

Harmonic voltage (%)

3,5

3

6

5

Odd harmonics multiples of 3 (note)



15

21

3

9

5

1,5

0,4

0,3


2

4

6

8

Even harmonics


0,5

0,5

2

1

17 ≤ h ≤ 49 2,27 x (17/h)-0,27 21 ≤ h ≤ 45 0,2 10 ≤ h ≤ 50 0,25 x (10/h)+0,25

Note: The levels indicated through even harmonics multiples of three are applied to the homopolar harmonics.

So this, in a 3-phase distribution line without neutral cable with no load connected between a phase and ground, the value of the harmonics order 3 and 9 can be lower enough than compatibility levels, depending on the distribution line imbalance.


Standards & Regulations | Summary

SUMMARY

It is necessary to clarify that in order to fulfill standard regulations, it is required to fulfil the following norms:IEC61000-2-2, IEC61000-2-4 or IEC61000-2-12 depending on the location where the equipments are connected.

If those regulations above mentioned are fulfilled and the THD values in current are above the specified ones in document IEEE-519, then it is possible to state that both the installation and the equipments are have compliance with the norms.

Distortion limits in voltage of a low voltage system (THDv):

THD (voltage)

Special applications

3%

General system

5%

In special applications are included hospitals and airports.

Dedicated system

10%

Distortion limits of current for general distribution systems (THDi):

Isc/IL

<20*

20<50

50<100

100<1000

>1000

<11

4.0

7.0

10.0

12.0

15.0

Maximum harmonic current distortion

Order of each harmonic

11≤h<17 17≤h<23 23≤h<35

2.0

1.0

0.6

3.5

4.5

5.5

7.0

2.5

4.0

5.0

6.0

1.0

1.5

2.0

2.5

35≤h

0.3

0.5

0.7

1.0

1.4

Isc: Maximum short circuit current in the PCC

IL : Maximum demanded current by the load in the PCC

TDD

5.0

8.0

12.0

15.0

20.0


Index



> Measurement

> Effects


> Solutions

- Passive Filters

- FREEMAQ

- Active Filters


> Competitors


Solutions

 PASSIVE FILTERS



Input Coils - Choke Inductances



Passive 5

th

& 7

th

Notch Filter

 HIGH INPUT IMPEDANCE NOTCH FILTER



Low Harmonic FREEMAQ

 ACTIVE FILTERS.



Controller bridge rectifier - Active filter



VSD Active Front End

 MULTIPULSES DRIVES



Low voltage 12, 18, 24 pulses drives



Medium Voltage Multipulse Drive


Solutions | Passive filter

Passive Filter Input Coils – Choque Inductances

These passive filters can be placed in the rectifier bridge input , realizing a double mission:

• First of all, they protect to the rectifier from voltage variation of the mains.

• On the other hand, they filter the produced harmonics making softer the sinusoidal wave of current.

They can also be placed in the DC bus . The rectifier bridge will not be as protected as in the previous configuration, but this is always a low cost option.

SD700 Frames 3 on SD700 Frame 1 & 2


Solutions | Passive filter | 5th & 7th Notch Filter)

VSD

Zg

L1

L2

C1 C2 f 5th f 7th

 1) LC Filters designed for an Specific

Harmonic and Grid Impedance ( Zg)

 2) Variation on Zg → Increase THDi

 3) Variation on Zg → May cause Resonance

 4) Valid for original installations, not compatible with new Grid Loads

1 st 5 th 7 th

Grid Impedance (Zg) Variation

1 st 5 th 7 th


Solutions | Low Harmonics FREEMAQ

L1

Zg

L2

L3

C1

1 st 5 th 7 th

 1) LCL Filters designed for General Harmonic attenuation and Independent from the

Grid Impedance ( Zg)

 2) Variation on Zg → Do NOT affect to THDi . Z

L1

>> Zg

 3) Built in with robust electric components

 4) Never cause resonance


Solutions | Active Filter - Controller bridge rectifier -(AAF)

Zg

C1

L2

L1  1) Works as a Current source.

 2) LCL Filter in Parallel.

 3) Smaller size of L1 and L2 , designed for switching frequency.

 4) Built in with Semiconductors and control software - reduce robustness

CONTROLLED BRIDGE RECTIFIER


Solutions | Active Filter | VSD Active Front End (AFE)

L1 L2

VSD

Zg

C1

 1) Regenerates the braking energy 4 quadrants drive . Increase the overall efficiency

 2) Serie LCL Filter

 3) Smaller size of L1 and L2 , designed for switching frequency.

 4) Built in with Semiconductors and control software reduce robustness


Solutions | Active Filter | Multipulses

The 12 , 18, 24 pulses drive have two, three or four rectifier bridges and the input voltage of each rectifier bridge is 30º / 15º / 7,5º diphase each other

PULSES

6

12

18

24

THDi (%)

< 40 %

< 15 %

< 9 %

< 5%

 To do that, it is needed a special transformer with multiple secondary windings is required.



12 PULSES ELECTRIC SCHEME



12 PULSES RECTIFYING BRIDGE

We can suppose a quasi ideal system applied to the rectifier, considering squared wave signal as reference. Having into consideration that the double secondary, explained before, enters a 30º phase shift in the currents applied to each rectifier, the result is a waveform much more sinusoidal in the inverter bridge:


Solutions | THDi variation with load

FILTER

TECHNOLOGY

Passive 5th & 7th

Notch Filter

Low Harmonic

FREEMAQ

Active Filter

VSD

Active Front End

LOAD

60%

7% (*)

≈6.5%

≈10%

≈10%

LOAD

75%

6% (*)

≈5%

≈8%

≈8%

LOAD

100%

≤5% (*)

≤5%

≤5%

≤5%

 (*) : Depending on the Grid Impedance Zg. Notch filter Re-design for grid load changes .


Solutions | Efficiency variation with load

FILTER

TECHNOLOGY

Passive 5th & 7th

Notch Filter

Low Harmonic

FREEMAQ

Active Filter

VSD Active Front

End

LOAD

60%

≥ 96.5

≥ 96.5

≥ 96.5

≥ 96

LOAD

75%

≥ 97

≥ 97

≥ 97

≥ 96.5

LOAD

100%

≥ 97.5

≥ 97

≥ 97

≥ 97


Solutions | Multipulses | MV

XMV660 is multi-cell VFD with series multi-cell VFD with series-connect units, high voltage input, high voltage output.

VFD is composed of transformer, power cells and control system.

Communication between power cells and control system is performed by optic fibre that can handle the problem of separation between heavy current and light current as well as electric magnetic harassment.

3kV

3.3kV

24 PULSES

TRANSFORMER

FAN FAN

3 FANS

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

GND

PC: Power Cell



Structure and power cell working principle

Each power cell is AC-DC-AC voltage source and low voltage transformer with 3-phase input, single phase output.

The rectifying side of power cell is rectified by diode 3-phase full bridge in the mode of not-controllable full wave.

Electrolytic capacitor is used to filter wave and store energy in the middle, the output side is formed by 4 pieces of

IGB in the form of H bridge.

Diode does not control rectification, power factor of single power cell is 0.97. Capacitor can buffer power supply impact. Equipment can keep on working in case of insufficient voltage or power off within short time.



Control over Output Voltage of Power Cell

At any moment, there are 3 types of possible output voltage. If A+ is on with B-, the output voltage from U to V is +Ud, if B+ is on with A, output voltage from U to V is –Ud, if A+ is on with B+ or A- is on with

B-, output voltage from U to V is 0V.

In the end, equal amplitude PWM wave form can be obtained from U,

V output terminal through control on/off on the IGBT A+ 、 A、 B+ 、

B-.



Frequency and Voltage Varying principle of Power Cell

Forma de onda salida PWM durante Frecuencia de Alta Conmutación

Frequency of output voltage of power cell is changed by altering the cycled period between positive voltage and negative voltage of PWM wave form.

Size of AC basic wave of output voltage from the power cell is changed by altering duty ratio between positive and negative voltage of PWM wave form.

Forma de onda de salida PWM durante Frecuencia de Baja Conmutación



Output Connection of Power Cell

Output of neighboring power cells are connected in series in “Y” form, which can realize high voltage output. Each power cell undertakes 1/n phase voltage, 100% motor current, 1/3n output efficiency.

For 6KV VFD , if 5 steps in each phase are connected in series, each power cell can output 693V , phase voltage is 3464V , wire voltage is 6000V . Unit DC Bus voltage is lower than 980V. IGBT resisting 1700V can be adopted.

3kV

3.3kV

24 PULSES

TRANSFORMER

FAN FAN

3 FANS

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

R

S

T

PC

GND

PC: Power Cell



Q1 Q3

Q2 Q4

En cualquier momento, la tensión de salida que cada célula puede ofrecer es:



Tensión= +600V en caso de que Q1 y Q4 estén en ON.



Tensión= -600V en caso de que Q2 y Q3 estén en ON.



Tensión= 0V en caso de que Q1 y Q3 estén en ON ó si Q2 y Q4 están en ON.



Multi-level Signal Generation

Detail Level 1 :

Power cell A2 offers 600V at the output, power cells A1 and A3 offer

0V. Therefore, the voltage is +600V .




.

Detail Level 2:

Power cells A1 and A3 offer 600V at the output, power cell A2 offers 0V.

Therefore, the voltage is +1200V.




.

Detail Level 3:

.

The three power cells A1, A2 and A3 offer 600V at the output each one.

Therefore, the voltage is +1800V.



Producing mechanism of Multi-cell and Phase-shifting PWM

CP1

CP2

CP3

Power cell in the same phase outputs basic wave voltage with the same amplitude and phase position. But the carrier wave of serial connected cells are separated at certain electric angle.

Phase shifting of triangle carrier wave is 360 ° /n electric angle of carrier wave.

CP1+CP2+CP3



Phase Voltage and wire Voltage of Multi-cell Phase shifting Output

Wave form of phase voltage and wire voltage (take 3 grade as example).

As for n grade system, there are 2n+1 cells in the phase voltage and 4n+1 cells in the wire voltage. If the modulating frequency of power cell is “f”, the equivalent on/off frequency of output wire voltage is 2nf. The on/off frequency of IGBT is smaller (the on/off loss is also small), the equivalent on/off frequency of output is very high. As there is wave filtration of induction in the motor, current content of output harmonic is very low.

N

U

V

W


Index



> Measurement

> Effects


> Solutions

- Passive Filters

- FREEMAQ

- Active Filters


> Competitors


Competitors

SUPPLIER A

1.

DC CHOKES.

38% of drives standard built in

62% of drives external option

2.

LINE CHOKES.


OTHER SUPPLIER

DRIVE


Competitors

SUPPLIER B

1.

DC CHOKES.


2.

LINE CHOKES.



Competitors

SUPPLIER C

1.

DC CHOKES.


2.

LINE CHOKES.


01. ELECTROMAGNETIC COMPATIBILITY (EMC)

Electromagnetic Compatibility (EMC)

Total Harmonic Distortion (THD)

Electromagnetic Compatibility (EMC)

02 Total Harmonic Distortion (THD)

Drive dV/dt Losses

Drive dV/dt

Losses

ELECTROMAGNETIC COMPATIBILITY (EMC)

Standards & Regulations

The CE certification for Variable

Speed Drive requires compliance with directive

IEC61800-3 compliance

Standards & Regulations | 61800-3

Standards & Regulations | 61800-3

Standards & Regulations | 61800-3