EMC FLEX BLOG A site dedicated to Automotive EMC Testing for Electronic Modules

The top 10 causes of car fires:

1. Fuel System Leaks (Gasoline above 257 Celsius will ignite by itself)
2. Electrical System Failures (ICE car battery charging cycles can cause explosive hydrogen gas ignited by sparks from faulty/loose wiring)
3. Spilled Fluids
4. Overheating Engines
5. Overheating Catalytic Converters
6. HEV & EV Batteries
7. Arson
8. Car Crashes
9. Poor Maintenance
10. Design Flaws

Electric Vehicle Lithium-Ion Battery Packs are made of hundreds to thousands of battery cells that contain flammable liquid electrolytes. These lithium-ion battery cells can generate enough heat to ignite the electrolyte during the thermal runaway process. A short-circuit between cell's two electrodes can result in heat that increases due to chemical reactions until the electrodes burst into flame. Tesla developed a fast cooling system to prevent neighbouring battery-cells from catching fire if such thermal runaway event occurs. However, the cooling system cannot prevent spreading the fire if the battery-pack gets damaged by a large metal object as result of a collision. Among the fire safety solutions adopted by Tesla:

1. battery-pack protect by a thick hardened aluminum housing
2. firewall used to isolate the passenger compartment
3. suspension software set to increase the battery-pack distance to ground at highways speeds
4. Improved electrode's materials to increase safety of cells
5. development of non-flammable electrolyte

Controlling Battery Charging

EV and PHEV battery charging is handled through a sophisticated controlled rectifier that takes power from the plug, at 120 or 220 volts alternating current, which is converted to direct current for the battery. The charging voltage needs to be carefully monitored since overcharging can reduce battery life and lead to fire risks. EVs and PHEVs may use in-vehicle systems such as GM’s OnStar and Ford’s Sync to communicate with the charger, allowing the monitoring of the battery state of charge through an Internet-enabled phone. Similarly, the charger may communicate with a smart meter through the Internet, allowing charging to occur when electricity rates are lowest.

Ford Battery-Pack

GM Volt Battery-Pack

 

Nissan Leaf Battery-Pack

EVBatteriesPart1.pdf (4.74 mb)

EVBatteriesPart2.pdf (5.27 mb)

EVBatteriesPart3.pdf (4.29 mb)

EVBatteriesPart4.pdf (5.33 mb)

EVBatteriesPart5.pdf (3.72 mb)

Christian Rosu

• ICNIRP GUIDELINES FOR LIMITING EXPOSURE TO TIME‐VARYING ELECTRIC, MAGNETIC AND ELECTROMAGNETIC FIELDS (UP TO 300 GHZ) ICNIRP_1998.pdf (647.6KB)
  
• ICNIRP GUIDELINES FOR LIMITING EXPOSURE TO TIME‐VARYING ELECTRIC AND MAGNETIC FIELDS (1 HZ – 100 kHZ) ICNIRP_2010.pdf (641.5KB)
• ICNIRP Fact Sheet on the Guidelines for Limiting Exposure to Time-Varying Electric and Magnetic Fields (1Hz - 100 KHz) ICNIRP_2010_FactSheet_LF.pdf (116.1KB)
• ICNIRP GUIDELINES ON LIMITS OF EXPOSURE TO STATIC MAGNETIC FIELDS ICNIRP_static_2009.pdf (270.3KB)
• ICNIRP Fact Sheet on the Guidelines on Limits of Exposure to Static MF ICNIRP_FactSheet_Static.pdf (93KB)
• Environmental Health - EXTREMELY LOW FREQUENCY FIELDS Extremely_Low_frequency_fields.pdf (4MB)

Christian Rosu

Pros:

• Fast Start, very quiet and very smooth, no engine vibration, no oil or gas smell.
• High torque, very silent and responsive acceleration.  Tesla model S can go from zero to 60 mph 3.1 seconds.Electric drivetrains are generally much simpler and more reliable.
• Home recharging for house owners. Perfect for EV drivers with home solar panels system.
• Cheaper to operate & maintain (1/3 from gasoline cost, no exhaust systems, don’t need oil changes).
• No carbon emissions if operated in regions with grid based on hydro, wind, or solar.

Cons:

• Limited range (80 to 100 miles) and due to lack of charging stations infrastructure exploring new routes or road deviations are risky.
• The cost of EV batteries is very high ($10,000), their life expectancy is modest (5 years), and their performance drops every year lowering the driving range. EV battery’s power will drop in very cold weather. Replacing & disposal of EV batteries in your garage is not anymore possible.
• The average cost of EV is about $40,000 in spite of governmental incentives.
• We still see a considerable number of EV makers recalls.

Christian Rosu

The carbon emissions from electricity generation are measured in tones of CO2 emitted per gigawatt hour of electricity produced.

• tCO2e/GWh = 0 for hydroelectric, nuclear and renewable energy
• tCO2e/GWh = 500 to 600 for natural gas power plants
• tCO2e/GWh = 1000 for coal-fired power plants

In countries that generate much of their electricity by burning coal charging EV's battery will significantly boosts carbon emissions. Even in Canadian provinces Alberta, Saskatchewan and Nova Scotia, electric cars generate more carbon pollution over their lifetimes than gas-powered cars. To really contribute to a greener environment you have to buy rather an HEV than EV. Sources

Christian Rosu

Purpose of the LISN:
1. Provide well defined RF impedance to the DUT.
2. The 1μF & 50μH filter isolates the noise that is put on the supply lines by DUT from feeding back to the power supply / battery.
3. Provide a low impedance path for the noise to be measured at the output port of the LISN coupling the interference voltage generated by DUT via 0.1μF to the analyzer or receiver.

The role of the LISN is to isolate the DM current and CM current from the power supply, and to minimize the impact of the CM current by returning it to its sources.

The wire harness inductance for large systems (aircraft) is 50μH whereas for small systems (automotive) is 5μH. However, the LISN selection criteria should be based on the frequencies of the measurements required.

Types of LISN

1. V-LISN: Unsymmetrical emissions (line-to-ground)
2. Delta-LISN: Symmetric emissions (line-to-line)
3. T-LISN: Asymmetric emissions (mid point line-to-line)

There are two types of V-LISN with different impedances.

• 5 µH inductance (CISPR 16-1-2, CISPR 25, ISO 7637, SAE J1113-41, DO160) are normally used to measure equipment for vehicles, boats and aircrafts connected to on-boards mains with DC or 400 Hz.
• 50 µH according to CISPR 16-1-2, MIL STD 461 and ANSI C63.4 is intended to operate at mains frequencies of 50 Hz or 60 Hz.

The T-LISN measures the asymmetric disturbance voltage (common mode voltage) and provides it to an EMI Receiver. It is normally used for measuring telecommunication and data transmission equipment connected to symmetrical lines as e.g. twisted pairs.

CISPR-25 (Ed 3.0)
A network inserted in the supply lead or signal/load lead of apparatus to be tested which provides, in a given frequency range, a specified load impedance for the measurement of disturbance voltages and which may isolate the apparatus from the supply or signal sources/loads in that frequency range.
CISPR-25 (Ed 3.0) & ISO-11452-2:2004 & ISO-11452-4
The AN impedance ZPB (tolerance ± 20 %) in the measurement frequency range of 0.1 MHz to 100 MHz it is measured between the terminals P and B with a 50 Ω load on the measurement port and with terminals A and B short-circuited.

The 1μF capacitor is populated in CISPR-25 LISN; R=1Kohm.

ISO 7637-2:2011 & ISO-11452-2:2004 & ISO 7637-2:2004
The artificial network is used as a reference standard in the laboratory in place of the impedance of the vehicle wiring harness in order to determine the behavior of electrical/electronic devices.
ISO 7637-2:2011 & ISO 7637-2:2004
The resulting values of impedance ZPB, measured between the terminals P and B while terminals A and B are short-circuited, are given in figure below as a function of frequency assuming ideal electric components. In reality, the impedance of an artificial network shall not deviate more than 10 % from the given curve.

No 1μF populated in ISO 7637-2 LISN; R =50 ohm, C is function of voltage.

Sample setup: CISPR-25 require separate LISN for B+ and GND lines.

Christian Rosu