Transcript Document 7492937

BLACK&DECKER
Jess Dibelka
Mark Steimer
12/10/07
Laura Traub
Julianne Twomey
Introduction
• Lithium-ion battery pack
• Metal Oxide Semiconductor Field Effect
Transistor (MOSFET)
• Electrical switch that controls the speed
of the drill head
• Introduces an electrical resistance
• Continuous current loading raises MOSFET
temperature
MOSFET
Trigger
Motor
• Small Voltage applied to gate
• Creates electric field across +p substrate
• Conduction bands allow large currents to flow through
MOSFET
Objectives
Goal: Reduce the temperature of the MOSFET junction during
use to avoid failure
75°C
(OSHA)
175°C
98 °C
(Plastic Deformation
Temperature)
Quantity of Energy Absorbed
18V Circular Saw ABR Test Loading
Current (A)
40
Trigger
30
20
Rj
10
0
0
200
400
600
800
1000
Motor
Time (s)
Heat Energy
MOSFET
E   I R j t  1401.85 J
2
Circular Saw Current Profile Used to Over Constrain Design
Target Values
Ranking
Concept Metrics
Target Value
1
2
Quantity of Heat Absorbed
Mass of Device
1401.85 J
20.3 g
3
4
Volume of Device
o
Qty Battery Cycles Before Tj = 175 C
<12 cm
2
5
6
7
8
9
MOSFET Orientation
Unit Production Cost
Number of Assembly Parts
Number of Processing Steps
DOF of Device Within Casing
0 o Angle
$0.13
3
4
0
3
Heat Removal Concepts
Final Heat Sink Concept
Design Issues
•
•
•
•
MOSFET Attachment/Orientation
Geometric fit within handle
Heat Absorbed
Thermal
– Thermal Gradient
– Cp, K, ρ
Required Volume
Cast
• Aluminum 356
• V = 9.37cm3
Stamped
• Aluminum 6061
• V = 9.99 cm3
Using Law of Energy Conservation
E
3
V
 9.37cm
c p T
T  98 C  40 C
o
o
Volume Analysis Heat Sink
Detailed Design Process
1) SolidWorks Modeling
2) Geometrically Fit in 3D
Drill Handle
Solid Works Design
3) Thermal Model of Drill
Handle
Thermal Model Drill
Handle
Fit Design in Drill Handle
Stamped Concepts Eliminated
• Maximum gage thickness
of 3 mm
•Stamping designs occupy
more space than cast
• Copper mass
significantly higher
Material
Mass (g)
Al 6061
26.98
Cu
62.78
3 MOSFET Mounts = 3 Cast Designs
MOSFET wires un-bent
Flange
MOSFET wires rotated 90o
Oval
MOSFET wires bent 45o
D-Sink
Thermal Modeling
•
Initial Solid Modeling
• Apply 1401 J of energy to heat sink
•
Natural convection from heat sink
• Apply adiabatic wall on outer drill
handle
1401 J
97.4 oC
95.3 oC
Heat Sink Temp Profile
Heat Sink in Drill Handle
Thermal Modeling Results
Design Constraints
Max Heat Sink Temperature
(Constraint < 98 oC)
Max MOSFET Temperature
(Constraint < 175 oC)
Max Drill Handle Temperature
o
(Constraint < 75 C)
Flange
Oval
D-Sink
81.2
75.5
81.4
Heat Sink Temp Surface Plot
85.3
76.3
83.4
67.4
44.0
62.2
Drill HandleTemp Surface Plot
Testing Overview
1) Indicate Heat Sink temperatures with simplified Box
Test
2) Test Heat Sink in Drill Handle
a. Heat Sink Thermal Repeatability
b. Test Procedure Repeatability
Testing Procedure
Test 1: Box Test
1) Attach thermocouples
2) Attach resistor and apply
thermal grease
3) Place Heat Sink in Box
Thermocouples
4) Apply 1401 J of energy over
732 s
5) Obtain temperature profiles
Testing Set-Up
Testing Procedure
Test 2: Drill Handle Test
1) Identical procedure
2) Heat sink placed in drill
handle
3) Thermal repeatability: Flange
tested 3 times
4) Test procedure repeatability:
Oval tested 2 times
Thermocouples
Testing Data Collected
For each trial collected thermocouple readings for:
•Heat Sink
•MOSFET
•Handle
Heat Sink Testing Conclusions
• Relatively No Thermal Change Between Heat Sinks
• Flange has Best MOSFET Attachment
• Therefore : Flange is Best Design
•Heat Sink Loading and Test Procedure Proved Repeatable
Design Process Conclusion
FloWorks to Test Analysis
Heat Sink
Drill Handle
Box
Flange
Oval
D-Sink
10.42 ±.45
11.55 ± 2.46
9.36 ±.72
15.10 ± 2.26
15.31 ± 2.93
13.10 ± 2.46
Average ∆T (FloWorks - Testing) ± Standard Deviation
Temperature difference due to Adiabatic wall condition in Modeling.
Can re-design using FloWorks assuming 10oC Temperature difference.
Ultimate Re-Design
1) Incorporates 0° wire bend angle
MOSFET attachment
2) Use FloWorks to yield max heat sink
temperature of ~96oC.
3) Expect testing to yield a
temperature of ~86oC
4) Leaving a Margin of Safety of ~10oC
FloWorks ( C)
Expected Test
o
Results ( C)
Maximum MOSFET
o
Temperature 40 C Ambient
102.2
92.2
Maximum Outer Handle
o
Temperature 40 C Ambient
66.4
56.4
Maximum Heat Sink
o
Temperature 40 C Ambient
95.95
85.8
Ultimate
o
V = 6.45 cc
Cost Analysis
•Machinist
• 10 hrs at $70/hr
•Material
•$2/lb, 50% scrap
•Thermocouples
•Production cost
Validation Resources
Prototyping Machinist
Material
20 Thermocouples
Testing
Total
Cost ($)
$2,100.00
$0.72
$15.00
$2,115.72
•$30,000 tooling cost
•700,000 total parts
Production
Heat Sink Cost
$0.13
Path Forward- B&D
• Confirm Predicted Test Results of Ultimate Design
• Use Design Methodology to Develop Heat Sinks in Future
Tools
• Receive Cost Quotes from Heat Sink Suppliers
• Test Reliability of Bolt and Nut Attachment Under Long
Term Thermal Cycling
• Adapt If Needed To Fit Other Tools
Summary
•All constraints and target values are achieved in heat sink
design!!!
•Heat sinks and testing procedure are repeatable
• Difference in heat sink performance between FloWorks and
Testing is ~10oC
•New “Ultimate” heat sink is lighter and incorporates positives of
previous heat sinks
• Cost for Black and Decker to implement Ultimate is
approximately 13 ¢ per heat sink
Questions
Thank You:
Black and Decker
Daniel Brisach (Thermal Modeling Help)
Roger Stahl (Rapid Prototypes)
& Dr. Glancey
Test Data CV
Test Data Delta T
Test Data Delta T
Testing Target Value Results
Ranking
Constraint
Constraint
Constraint
Testing Prototype Metrics
Target Value
D-Sink Actual
Oval Actual
175 C
79.5
81.4
79.1
75 C
o
49.0
47.0
54.0
98 C
o
70.2
69.7
70.6
1401.9 J
Controlled
Controlled
Controlled
2 or 732 s
Controlled
Controlled
Controlled
1.1
2.1
0.6
Maximum MOSFET Temperature
@ 40 oC Ambient
o
Maximum Outer Handle Temperature
@ 40 oC Ambient
Maximum Heat Sink Temperature
@ 40 oC Ambient
1
Quantity of Heat Absorbed
4
Qty Battery Cycles or Time before T j= 175 C
8
Max Temperature Change
Ranking
Flange Actual
o
Testing Prototype Metrics
o
1 C
Flange Target
Flange Actual
D-Sink Target
D-Sink Actual
Oval Target
Oval Actual
2
Mass of Heat Sink (g)
25.91
25.26
25.78
24.80
29.82
25.05
3
Volume of Heat Sink (g)
9.39
9.36
9.34
9.19
9.36
9.28
Heat Sinks Satisfied the Constraints with ~ 20oC Margin of
Safety
Testing Results
Flange Repeatability
Thermocouple
Coefficient of Variability
1
2
3
4
5
0.083
0.077
0.004
0.076
0.082
6
7
8
9
10
0.009
0.002
0.047
0.027
0.028
Oval Test Repeatability
Thermocouple
Coefficient of Variability
Plain English
Statement
Example of CV  s/m
Poor control
Cv = .2
Fair control
Cv = .1
Tight control
Cv = .05
Excellent control
World class
Seldom achieved
Cv = .025
Cv = .0125
Cv = .000625
Courtesy of Dr. Glancey
Energy Analysis MOSFET
Ein   I R j t  1401.85 J
2
Total Energy Equation
Ein Tmax  TJ

t RJC  RTG
TJ  102 C
o
Actual MOSFET Junction Temperature
Energy Calculations
Total Energy (J)
Junction
Temperature
(oC)
2 Battery Packs
o
Resistance 150 C
1401.85
102.75
2 battery Packs
Resistance 100oC
1168.21
101.96
Rotor Lock
1160.70
103.48
Energy Analysis Heat Sink
Ein  Est  Vc p T
Ein
V
c p T
V  9.99cm
3
Volume of Heat Sink Required
Thermal Analysis Handle
Est  Eout  qcond  qconv
kA1
Eout  1.91W 
(THS  TP )  hA2 (THS  T )
L
o
TP  58.25 C
TP
Thermal Analysis Constants
W
k  .002
cmK
L  .3cm
1
A1  S . A.  4.3cm 2
6
A2  23.7cm 2
R150  .0063
R100  .0053
THS  98o C
THS  98o C
W
h  .002 2
cm K
t  732 s
o
C
RJC  .48
W
o
C
RTG  2
W
T  98o C  40 o C
Equation Constants
Material Properties
Testing Calculations
P(W )  I R
2
V  IR
P  1.91
R  .05
V  .309V
I  6.18 Amps