Variable Frequency AC Source

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Variable Frequency AC Source Students:

Kevin Lemke

Matthew Pasternak

Advisor:

Steven D. Gutschlag

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Outline

• Project overview• High level block diagram• Subsystems• Lab work• Equipment• Future work

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Project Goals

• Variable Frequency AC Source (VFACS)• Capable of delivering 208 [Vrms] and 5 [A]• Sine wave frequency range from 0 to 60 [Hz]

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Project Significance

• VFACS used to vary shaft speed in a three phase induction motors• Constant Volts/Hertz ratio to provide

variable torque & speed operation without exceeding motor current ratings

• Variable Frequency Drive (VFD)• Replaces control flow control valves in

pump systems• Replaces gear box speed control• Improve operating power factor

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[1]

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High Level System Block Diagram

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PWM Generation Controller

• Produces dual sided PWM signals for the Gate Drive Circuitry• Use a LabVIEW based controller and cDAQ module from

National Instruments• When completed, ability to control both single phase

and three phase systems

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Single-Phase PWM Generation Controller

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Single-Phase PWM Generation Controller • Produce TTL level PWM signals• Produce waveforms

representative of sine waves from 0-60 [Hz]• Combination of Upper and Lower

PWM signals• Produced from Upper and Lower

Triangle Waves

• Produce waveforms following appropriate V/Hz based on DC rail voltage

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Single-Phase PWM Generation Controller

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• Simulink based PWM Generation Controller• V/Hz control• Ideal LC Filter testing

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Gate Drive Circuitry

• High speed signal isolator and driver• Use optical isolators and gate driver chips to isolate and

amplify gate drive signals to the Inverter• Optical isolators and gate drivers chosen for speed and

robustness

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Initial Gate Drive Circuitry

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Gate Drive Circuitry

• Capable of switching at 1% duty cycle and 15 [kHz] switching frequency• Optical Isolator• 6N137 Optocoupler• Isolate cDAQ outputs from Inverter, Filter, and Load Voltages

• Gate Driver• IR2110• Amplify PWM from TTL level to Vge =15 [V]

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Redesigned Gate Drive Circuitry Changes• Replaced IR2110/6n137

with HCPL3120• Robustness• Real-estate• Simplicity

• Verified that this chip would provide the same switching speed as the IR2110

[2]

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Inverter

• PWM Signal Amplifier for AC machine application• Use IGBT pairs and DC rails to amplify PWM signal• IGBTs used for high voltage capability, low on-state

voltage, and availability• Single- and three-phase configurations

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Single-Phase Inverter

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Three-Phase Inverter

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Inverter Configurations

• Single-phase Inverter• Fairchild FMG2G75US60 IGBT Pair• Each IGBT will receive one PWM signal• Output one dual-sided PWM signal representing the necessary

sine wave• Have 0 and 100 [VDC] rails capable of providing 15 [A] for

testing

• Three-phase Inverter• Three single-phase inverters• Single-phase inputs 120⁰ out of phase from any other input pair• Capable of 5 [A] per phase

• IRF520N MOSFETS for testing17

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Filter• LC filter

• Used to extract sine wave encoded in PWM signal

• Three identical filters used (one for each phase)

• Components rated for 400 [V] and 15 [A]• Practical filter in LRC configuration

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LCs

L

Rs

LCV

V

i

o

1

1

2

LCw

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LRC Filter Design Equations

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Filter Updates

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Practical LRC Filter Frequency Response

LR Motor Filter Frequency Response

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Filter Updates

• Analysis of three phase induction motor filtering capabilities• LRC meter to measure L & R of the motor to be used for

testing• Comparison filtering characteristics of motor and

proposed LC filter• Determined that inherent LR filter in the motor can

replace the Filter subsystem

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Load

• Overall system output used for testing• Initially resistive-inductive (RL) for both single and

three-phase systems• Final tests will be performed on a three-phase induction

motor• Shall be able to draw the rated power from the system

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Opto-coupler Simulation

• 6N137 Opto-coupler Simulation]

• PSPICE Circuit

• Exported to Excel for plotting

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Opto-coupler Simulation

Opto-coupler Simulation

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.00000 0.00010 0.00020 0.00030 0.00040 0.00050 0.00060 0.00070

Time

Am

litu

de

(V)

Vin

Vo

• Inverted output• Minimal rise time•15 [kHz] test input signal

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Gate Driver Testing• Gate Driver and Opto-

coupler construction• HCPL3120 Gate Driver

construction• HCPL3120 Gate Driver

testing with IFR520N MOSFET single phase inverter• DC rails 0 and 18 [VDC]• +DC rail/2 5 [V]

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Single-Phase Inverter Test with IRF520N MOSFET

Ch1 Load Voltage

Ch2 Load Current

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LabVIEW Data Type Testing• Basic cDAQ Interface• Analog Input• Digital Output (TTL)

• Basic PWM Generation Controller in LabVIEW for data type testing• Point by Point vs Waveform data types

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Basic Controller & Data Type Simulation

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• Simulation of basic, single-phase PWM generation controller• 1 [Hz] sine wave• 10 [Hz] triangle wave• 1 [kHz] sampling frequency

Single-Phase PWM Generation Controller Simulation

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Controller Design

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• Based on Simulink model

• Uses waveform data type

• Configured for three phase operation

• Built and output digital waveform from sine & triangle wave comparison

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Sine and Triangle Wave Generation

• Generate sine and triangle waves• User specified signal and sampling frequency• Extract amplitude value for comparison

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PWM Signal Generation

• Comparison of upper and lower triangle waves to sine wave for A-phase• Digital waveform generation• Used sampling information from

sine and triangle wave generation• Digital waveform sent to output

stage• B & C phase comparison uses

120° and 240° phase shift respectively

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Output Stage Using DAQmx Toolkit

• Digital waveform input to while loop• Create and write to

physical channel on cDAQ• B & C phase output

stages follow this design

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Controller Simulation

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• Simulation of basic, three-phase PWM generation controller• 1 [Hz] sine wave• 15 [kHz] triangle wave• 150 [kHz] sampling frequency

Three-Phase PWM Generation Controller Simulation

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Low Frequency Output Testing

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• PWM Generation Controller Test• 1 [Hz] Sine wave• 10 [Hz] Triangle Wave• 1 [kHz] sampling frequency

Single-Phase Simulation

Single-Phase Low Frequency Simulation

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Low Frequency Output Testing

• Oscilloscope graph of low frequency output test• Output matches digital

waveform from LabVIEW scope

Single-Phase Low Frequency Output Test

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High Frequency Output Testing

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Single-Phase Upper Half PWM High Frequeny Signal Simulation

-0.2

0

0.2

0.4

0.6

0.8

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1.2

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009

Time (s)

Am

plitu

de (B

oole

an)

• PWM Generation Controller Test

• 60 [Hz] sine wave and 15 [kHz] triangle wave

• LabVIEW scope reading exported to excel

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High Frequency Output Testing

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• Output from cDAQ as seen by oscilloscope

• 60 [Hz] sine wave 15 [kHz] triangle wave

• Waveforms from LabVIEW scope and oscilloscope match

Single-Phase Upper Half PWM Signal High Frequency Output Test

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Equipment & Parts List• LabVIEW Student Edition• NI-cDAQ-9174 Data Acquisition Chassis• NI-9401 Digital I/O• NI-9221 Analog Input Module • NI-9211 Thermal Couple• IR2110/2113• 6N137 Opto-coupler • HCPL3120 Gate Driver• IRF520 MOSFET• FMG2G75US60 IGBT Pair with anti-parallel diodes• 7MBP75RA060-09 Inverter module• Sources and Scopes available in Power Lab

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Future Work

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• Current Year• PWM Generation Controller

• Volts/Hertz ratio• Simultaneous upper and lower PWM outputs

• Load voltage feedback input• Future Years• Single phase inverter with FMG2G75US60 IGBT pairs• 7MBP75RA060-09 Inverter module• Three phase implementation

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Questions?

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References•[1] http://www.globalindustrial.com/p/motors/ac-motors-definite-purpose/explosion-proof-motors/baldor-motor-idxm7170t-10-hp-2700-rpm?infoParam.campaignId=T9F&gclid=CJa-kMDzhb4CFexcMgodOBsAWA&gclsrc=aw.ds•[2] www.avagotech.com/docs/AV02-0161EN

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Switching Speed Calculation

• FMG2G75US60 minimum switching speed• Switching speed = Gate Charge [nC]/ Gate Current [A]• Switching speed = 200 [nC]/ 2 [A] * 4 = 0.4 [μs] using maximum current for

IR2110 and HCPL-3120

39Plot of Gate Charge Characteristics for FMG2G75US60

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Datasheets

• http://www.fairchildsemi.com/ds/6N/6N137.pdf• http://www.daedalus.ei.tum.de/attachments/article/257/IR2110_IR2

110S_IR2113_IR2113S.pdf• http://pdf.datasheetcatalog.com/datasheet/fairchild/FMG2G75US60.

pdf• http://www.datasheetcatalog.com/datasheets_pdf/H/C/P/L/HCPL-31

20.shtml• https://www.futurlec.com/Transistors/IRF520.shtml

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Flow Chart

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RLC Filter Design Equations

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LCs

L

Rs

LCV

V

i

o

1

1

2

LCw

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L

CR

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2

QF b

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0

LCs

L

Rs

LCV

V

i

o

1

1

2

LCw

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RLC Filter Response

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Pictures

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