Variable Frequency AC Source
Students:
Kevin Lemke
Matthew Pasternak
Advisor:
Steven D. Gutschlag
1
Outline
• Project overview
• High level block diagram
• Subsystems
• Lab work
• Equipment
• Future work
2
Project Goals
• Variable Frequency AC Source (VFACS)
• Capable of delivering 208 [Vrms] and 5 [A]
• Sine wave frequency range from 0 to 60 [Hz]
3
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
[1]
4
High Level System Block Diagram
5
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
6
Single-Phase PWM Generation
Controller
7
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
8
Single-Phase PWM Generation
Controller
• Simulink based PWM
Generation Controller
• V/Hz control
• Ideal LC Filter testing
9
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
10
Initial Gate Drive Circuitry
11
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]
12
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]
13
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
14
Single-Phase Inverter
15
Three-Phase Inverter
16
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 testing
17
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
1
Vo
LC

Vi s 2  R s  1
L
LC
w0 
LRC Filter Design Equations
1
LC
18
Filter Updates
Practical LRC Filter Frequency Response
LR Motor Filter Frequency Response
19
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
20
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
21
Opto-coupler Simulation
• 6N137 Opto-coupler Simulation]
• PSPICE Circuit
• Exported to Excel for plotting
22
Opto-coupler Simulation
6.00
5.00
Amlitude (V)
• Inverted output
• Minimal rise time
•15 [kHz] test input signal
4.00
Vin
3.00
Vo
2.00
1.00
0.00
0.00000
0.00010
0.00020
0.00030
0.00040
0.00050
0.00060
0.00070
Time
Opto-coupler Simulation
23
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]
Ch1 Load Voltage
Ch2 Load Current
Single-Phase Inverter Test with IRF520N MOSFET
24
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
25
Basic Controller & Data Type Simulation
• 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
26
Controller Design
• Based on Simulink
model
• Uses waveform data
type
• Configured for three
phase operation
• Built and output
digital waveform from
sine & triangle wave
comparison
27
Sine and Triangle Wave Generation
• Generate sine and triangle
waves
• User specified signal and
sampling
frequency
• Extract amplitude value for
comparison
28
PWM Signal Generation
• Comparison of upper and lower
triangle waves to sine wave for Aphase
• 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
29
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
30
Controller Simulation
• 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
31
Low Frequency Output Testing
• PWM Generation Controller Test
• 1 [Hz] Sine wave
• 10 [Hz] Triangle Wave
• 1 [kHz] sampling frequency
Single-Phase Simulation
Single-Phase Low Frequency Simulation
32
Low Frequency Output Testing
• Oscilloscope graph of low
frequency output test
• Output matches digital
waveform from LabVIEW scope
Single-Phase Low Frequency Output Test
33
High Frequency Output Testing
1.2
1
0.8
Amplitude (Boolean)
• PWM Generation
Controller Test
• 60 [Hz] sine wave
and 15 [kHz]
triangle wave
• LabVIEW scope
reading exported to
excel
0.6
0.4
0.2
0
0
-0.2
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
Time (s)
Single-Phase Upper Half PWM High Frequeny Signal Simulation
34
High Frequency Output Testing
• 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
35
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
36
Future Work
• 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
37
Questions?
References
• [1] http://www.globalindustrial.com/p/motors/ac-motors-definite-purpose/explosion-proofmotors/baldor-motor-idxm7170t-10-hp-2700-rpm?infoParam.campaignId=T9F&gclid=CJakMDzhb4CFexcMgodOBsAWA&gclsrc=aw.ds
• [2] www.avagotech.com/docs/AV02-0161EN
38
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
Plot of Gate Charge Characteristics for FMG2G75US60
39
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/HCPL3120.shtml
• https://www.futurlec.com/Transistors/IRF520.shtml
40
Flow Chart
41
RLC Filter Design Equations
1
Vo
LC

Vi s 2  R s  1
L
LC
w0 
1
LC
F b

0

1
Q
  2
R C
 
2 L
42
RLC Filter Response
43
Pictures
44
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