Presented to EVAOSC
Wally E. Rippel
May 15, 2009
Goal of Today’s Talk
Review some fundamentals dealing with Energy, Environment, and EV’s. To lead a discussion on the topic of how to make the best possible EV drive motors
I am not at liberty to share “trade secrets”. So, all of you will provide the information
What BP Doesn’t Want U 2 Know
- 97% of U.S. transportation is powered by oil
- Less than 1% of U.S. electricity is generated from oil
- If electrified, the energy required to power ALL cars and All small trucks would be only 19% of the total electrical energy generated
- 0.3 kWh/mi x 2.4 trillion vehicle mi = 0.72 T kWh
- Energy generated (2008) = 3.73 T kWh
What Shell Doesn’t Want U 2 Know
- Wind generated electricity sells for less than $0.04/kWh with newest equipment; payback periods are less than 15 years
- The entire U.S. electrical load plus 19% can be provided by less than 1 million 3 megawatt wind generators in mid-west.
- Actual land use is negligible (square of 180 mi. on side, but 99% of land still available for farming)
How Do You Connect Wind Energy to Vehicles??
What metrics should we use??
How do they compare for the two cases??
- You Need an “Energy Carrier”
- We have two choices at hand
An Energy Synergy
Wind and Solar energy can power all vehicles. With internet control of charging rates, EV’s can add stability to the grid which means that a much greater fraction of the energy can come from wind and P.V. – further reducing the need for hydrocarbon energy U.S. Energy Policy
Policies which DO NOT make sense:
- “Drill Baby Drill” (unless its school work)
- Simply eliminating import of mid-eastern oil
- Using land for ethanol rather than agriculture
- Substituting coal for oil
Policies which DO make sense:
- Those which ultimately eliminate all carbon fuels
- Those which promote energy efficiency
- Those which encourage targeted scientific progress
Finally, We Get to Motors
What is the function of the drive motor in an electric vehicle? (Need to be careful here.) What parameters are important?
Consider the ACP-150 Motor
- Peak Shaft Power - 150 kW (at 6000 rpm)
- Cont. Shaft Power - 35 kW (at 6000 rpm)
- Peak Torque - 240 Nm (below 6000 rpm)
- Max. Speed - 13,500 RPM
- Peak Efficiency - 95% (8000 rpm, 100 Nm)
- Typical Pwr. Factor - 85%
- Weight - 45 kg
- Prismatic Volume - 32 liters
- Hi vol. mfg. Cost - $1500 (est.)
Physics Behind Motors
F = B x (L*I)
1 A thru 1 m wire in 1 T field gives force = 1 N
When applied, we get:
T = K*S4*B*J
S is a linear dimension
B is the magnetic field strength (T)
J is the current density (A/cm2)
Major Loss Components
Conductor Loss (Copper Loss)
Pcu = ρ*J2*V
Magnetic loss (Iron Loss)
PFe = K*Bα*fβ*V
f is the magnetic frequency
V is the material volume
This Is Where You Take Over
- What is the difference between brush-type and brushless-types??
- Why are brushes and commutators needed?
- Describe the construction and operation of a DC brushless motor
- Describe the construction and operation of an induction motor Comparisons
- What are the comparative advantages of brush-type and brushless motors?
- What are the comparative advantages of induction and DC brushless?
- When are DC brushless motors the “answer”
- When are induction motors the best “answer”
The Hard Stuff
- What determines the nameplate rating of a motor?
- What electrical parameters determine shaft torque?
- What electrical parameters determine RPM?
- What determines the maximum peak torque?
- What determines the maximum rpm?
What are the Key Parameters?
- Efficiency? What do you mean here?
- Power rating? What is that??
- What are the key figures of merit?
- P/mass or P/V – which is more important
- What do you mean by mass?
- What are they?
- Can you give some examples?
- How are trade-offs used in the design process?
- What pitfalls need be considered?
We start with a motor rated for 20 kW
(40 Nm, 5000 rpm); eff = 90%.
What would happen if we ran at 80 Nm, 5000 rpm?
What would happen if we ran at 40 Nm, 10,000 rpm?
What would happen if we ran at 80 Nm and 10,000 rpm?
If Torque and Speed are both increased, what good things happen? What prices do we have to pay?
- Can the Copper Loss be Reduced?
- What role does packing factor play?
- What role does temperature play?
- Is there anything better than copper?
Power is proportionate to RPM times Torque
- Can increased RPM substitute for incr. torque?
- What are the issues?
- Can Iron Losses be Reduced?
- What is the role of Lamination Thickness?
- What is the role of steel type?
- What is the role of temperature dependence?
A portion of the iron loss is due to the inverter PWM. Can anything be done to reduce this? Could it make sense to use more than one type of steel in a given motor?
- What is power factor?
- Why is high power factor important?
- How is power factor maximized?
Where would you focus development efforts?
- What directions do you feel would be a waste of time and money?
How Good Can it Get?
- Continuous Power/Mass - (0.78 kW/kg)
- Continuous Power/Volume - (1.1 kW/liter)
- Continuous Torque/Mass - (1.2 Nm/kg)
- Peak Efficiency - (95%)
- Efficiency at 5% power (>90%)
- Peak Power/Mass (3.3kW/kg)
- Cost/horsepower (OK, cost/kW) ($42/kW)
Expect Large improvements in both cost and performance for the next generation of EV motors. The real challenges are not technical, but political and psychological
WE NEED LEADERSHIP!
This product was added to our catalog on Tuesday 25 May, 2010.