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

• Starting point => Polaris Snowmobile

• Breakdown of snowmobile

• Electric motor– 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

Armature

+

-

NS

Interpoles

LOAD

Windings

1 2 3 4 5 6 7 8 9 10 11 12 13 14

SIMPLEX WAVE WINDING

1516

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

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.

Single Element

coil

Simplex Lap

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!

Y-Ax

is

S NN

Full Load Magnetic field

No Load Magnetic field

S N

Full Load Magnetic field

No Load Magnetic field

Y-Ax

is

Time

Neutral- No Load

and Full Load

No Load Neutral Full Load Neutral

No Inter-poles

With Inter-poles

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

• 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:• 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

S

N

Conductor

Movement

Field Flux

Current

+

_

Armature Physics

S

N

As the conductor changes

direction, the current and

voltage will also change

polarity

Armature Flux from Current

Simple Voltage production using a

conductor and two magnets of

opposite polarity

Load

Commutation Diagram50 A50 A050 A50 A50 A

50 A 50 A

Rotation

+ Brush

100 Amps

Current from

negative polarity

brush

Current from

negative polarity

brush

Coi

l Cur

rent

Distance0

+50

-50

Armature Coils undergoing Ideal

Commutation

Rotation

- Brush

Current going to

positive polarity

brush

Current Going to

positive polarity

brush

50 A50 A050 A50 A50 A

N S

Magnetic Field

between two

magnets

SN +

Armature induced EMAG

Rotation

N SRotation

New Magnetic field due to combination

++

+

+

+

+

90

Neutral

F

Vector F

repersents

MMF due to

Main poles

Fa F0

F

New Neutral

Fa

Vector Fa

represents

MMF due to

armature

induced current

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

ArmatureN S

Interpoles

Shunt Connection

Series Connection

LOAD

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

ArmatureNS

Interpoles

LOAD