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: 2CM6501Nameplate Ratings:• Voltage: 120VDC

• Armature Current: 167 A• Field Current: 10 APlace 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)WhereYc = 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 WhereYs = Coil pitchS = number of armature slotsP = 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-Axis

S NN

Full Load Magnetic field

No Load Magnetic field

S N

Full Load Magnetic field

No Load Magnetic field

Y-Axis

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

InterpolesShunt 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