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UNH ECE 791
Senior Project I
Design Proposal Presentation
Team
Members:
• Luke Vartuli
• Stephen Doran
• Doug MacMillan
Advisor:
• Dr. Gordon Kraft
Problem Statement
Problem:
• Noise
• Emissions
• Cost of operation
Solution:
• Electric snowmobile
Project Overview
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Starting point => Polaris Snowmobile
Breakdown of snowmobile
Electric motor
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Motor Theory
Motor Control
Pulse Width Modulation
PWM circuit
Power MOSFET’s
Mounting bezels
Battery type
Battery mounting
Timeline
Budget
Contributions
Starting Point
Donor Sled: 1996 Polaris Indy XLT
Breakdown of Snowmobile
Components Removed:
• Engine
• Exhaust
• Fuel tank
• Oil tank
• Starting battery
• Cooling system
Electric Motor
Specifications:
• Mfg: General Electric
• Model: 2CM6501
Nameplate Ratings:
• Voltage: 120VDC
• Armature Current: 167 A
• Field Current: 10 A
Place of Origin:
• WWII Era B-29 Aircraft
Armature
• Main component of the DCMG
• Uses multiple Armature windings for
conduction
• Undergoes Dynamo effect
Shunt DCMG
• Armature and Inter-poles are in parallel to
the Main poles.
• As load changes only a fraction of the field
will change.
• Safer, but has bad torque characteristics
Shunt Diagram
Interpoles
S
Armature
N
+
LOAD
Windings
Single Element
coil
16
1
2
3
SIMPLEX WAVE WINDING
4
5
6
Since the coils span every 3
commutator segments. This is
considered a simplex wave winding
with a triplex commutator pitch.
The Commutator pitch is as
follows….
Yc = (C ± m)/(P/2)
Where
Yc = Pitch of commutator
C = number of commutator
segments
m = the plex of winding, or in
context. The span of the coil from
one segment to another. For
instance since above winding is a
triplex. m= 3
P= number of poles
Simplex Lap
7
8
9
10
11
12
13
14
15
The coil pitch for this unit is as
follows….
Ys = S/P
Where
Ys = Coil pitch
S = number of armature slots
P = number of poles
It is important that no matter the
number you get you must round
down to the next integer. If its 12.6
then Ys = 12. If its 10 then Ys = 10.
Commutator
• “Assembly line for current transfer”
• As the commutator spins, current conducts
from the brush (-) to the commutator
bars the Load back to the Brush’s(+).
Inter-poles
• Maintains a neutral field flux over the
commutator as the load changes.
• By having a neutral field flux over the
commutator, this limits “sparking” on the
commutator which then leads to pitting
and damage. This will disrupt proper
commutation.
Inter-poles at work!
No Inter-poles
S
N
Full Load Neutral
Y-Axis
No Load Neutral
Time
Full Load Magnetic field
No Load Magnetic field
With Inter-poles
S
N
Y-Axis
Neutral- No Load
and Full Load
Full Load Magnetic field
No Load Magnetic field
N
Motor Control
How the motor will be controlled:
• Vary armature current, fixed field
• Pulse Width Modulation (PWM)
• Power MOSFET’s
Pulse Width Modulation (PWM)
• Use PWM to control armature, fixed field
• PWM controls power MOSFET’s
• As duty-cycle increases, switches on longer,
motor spins faster
PWM circuit
Power MOSFET’s
Pros:
• High current
• Fast switching
• Low resistance
Cons:
• No protection from fly
back voltage
• Get hot
Mounting Bezels
Key Components:
• Bed plate
• Motor
• Motor bezel
• Bearing Bezel
• Clutch assembly
• Orig. Motor Mounts
Battery Type
Flooded Lead Acid, Why?
• Availability
• Low cost
• Ease of configuration
• Ease of mounting
• Ease of connection
Source: www.carbasics.co.uk/inside_car_battery.gif
Battery Mounting
Configuration: Series
Nom. Voltage: 120VDC
Mounting: Battery rack
with top straps
Timeline
Budget
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Snowmobile: Donated
Electric Motor: Donated
Wire and misc. supplies: Donated
Mounting Bezel: $200
Batteries: $1000
Pulse Width Modulator: $150
Contributions
Donations:
• Snowmobile donated by Vincent Pelliccia
• DC Motor donated by Kevin White
• Wire and misc. electrical materials donated by Vartuli Electric, LLC
Support and Guidance:
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Prof. Kraft
Prof. Hludik
Prof. Clark
Prof. Smith
Adam Perkins
Matt Borowski
Thank you for your time
DC MOTOR THEORY
• Same concept as AC Motor/Generators
• Utilizes carbon brushes for DC
characteristics
Flemings right Hand rule
N
Current
Field Flux
Conductor
Movement
S
+
_
Armature Physics
Simple Voltage production using a
conductor and two magnets of
opposite polarity
N
S
Load
As the conductor changes
direction, the current and
voltage will also change
polarity
Armature Flux from Current
Commutation Diagram
Armature Coils undergoing Ideal
Commutation
50 A
50 A
50 A
0
50 A
50 A
50 A
50 A
Rotation
+ Brush
Coil Current
Current from
negative polarity
brush
Current from
negative polarity
brush
100 Amps
+50
0
Distance
-50
50 A
50 A
50 A
0
50 A
50 A
Current Going to
positive polarity
brush
Current going to
positive polarity
brush
Rotation
- Brush
Neutral
S
N
90
F
Vector F
repersents
MMF due to
Main poles
Magnetic Field
between two
magnets
Rotation
Vector Fa
represents
MMF due to
armature
induced current
+
N
Armature induced EMAG
S
Fa
New Magnetic field due to combination
+
+
+
S
N
Rotation
+
+
+
New Neutral
F
Fa
F0
Due to the field
MMF vector F and
the armature MMF
vector Fa combine
at right angles to
form the resultant
field MMF vector
F0
Armature current
Compound DCMG
• Utilizes both series and shunt
characteristics
• More common DCMG
Compund Diagram
Interpoles
Shunt Connection
N
Armature
S
LOAD
Series Connection
Series DCMG
• Poles, Inter-poles, and Armature all in
series.
• Change in load is directly proportional to
change in speed.
• Reduction in load can cause a “run-away”
motor which will then lead to mechanical
failure.
• High torque applications.
Series DCMG diagram
Interpoles
S
Armature
N
LOAD