EMC - EV

Electromagnetic Compatibility for Electric Vehicles

CISPR-25 RE per CS.00054:2018

CISPR-25 Generic Test Setup for compliance to CS.00054:2018

CS.00054 Radiated Emissions Block Diagram

The vertical monopole element is centered at 1m from the center of the 1.7m test harness. Note that 1.5m of the harness is running at 10 cm parallel with ground plane edge. The antenna counterpoise is placed +10/-20 mm vs GP. 

CISPR-25 Generic DUT Setup. The DUT is placed @ 20 cm from the edge of GP. The 1.7 m Test Harness is routed 90 degrees towards DUT.

The ground plane is connected to chamber's floor to a dedicated Earth Grounding Rod.

LISN (700 V DC / 500 A) & Load Simulator side of the test setup. 
DUT's B+ & GND lines are connected to LISN's outputs.

THE BICONICAL ANTENNA IN VERTICAL POLARIZATION. 
The antenna is centered on the 1.5m harness running at 10 cm parallel with GP edge.

THE BICONICAL ANTENNA IN HORIZONTAL POLARIZATION. 
The antenna is centered on the 1.5m harness running at 10 cm parallel with GP edge.

THE LOG PERIODIC ANTENNA IN VERTICAL POLARIZATION. 
The tip of antenna is 1 m away from the center of the test harness.

THE LOG PERIODIC ANTENNA IN HORIZONTAL POLARIZATION. 
The tip of antenna is 1 m away from the center of the test harness.

Octave Antenna Vertical Polarization with its aperture centered on DUT at 1 m distance from test harness.

Octave Antenna Horizontal Polarization with its aperture centered on DUT at 1 m distance from test harness.

Horn Antenna Horizontal Polarization with its aperture centered on DUT at 1 m distance from test harness.

Horn Antenna Vertical Polarization with its aperture centered on DUT at 1 m distance from test harness.

3-METER ALSE CHAMBER & Equipment Control Shielded Room.
 
ALSE CHAMBER EARTH GROUNDING ROD.

CISPR-25 RF emissions ambient test pitfalls

CISPR-25 is not very specific about device under test and support equipment configuration during chamber ambient test. The automotive OEM require the ambient for RE, CE-V, CE-I with support equipment energized. The test laboratories will typically disconnect VBATT line from LISN output. The GND line remains connected to LISN. By doing so is assumed that DUT is not energized. The support equipment remains connected to the input of the LISNs being turned on (energized). The CAN bus is powered but w/o traffic. It is unclear if the load simulator energized it means powered but inactive (standby). By activating PWM pulses as inputs for DUT it may yield unwanted CE-I and RE ambient noise. All these aspects must be clarified in the EMC test plan.

In the sample presented the CE-V ambient noise is well below the 6 dB requirement. However, this type of noise is being captured while DUT's integrated buttons are being pressed and released via a pneumatic system with no electrical connection to DUT or test ground plane. Specifying that DUT must be unpowered may not be enough, the DUT's buttons should not be mechanically activated, nor its inputs subjected to electrical signals.


Christian Rosu

EMC-CS-2009.1 CI 210 (Us Vp-p calibration issue)

ES-XW7T-1A278-AC Immunity from Continuous Disturbances: CI 210

This test refers to continuous disturbances produced by vehicle’s charging system that can affect DUT functions.



FMC1278 Rev2 vs EMC-CS-2009.1 - CI 210 Requirements

  • Level 2 requirements, as delineated in ES-XW7T-1A278-AC was removed in EMC-CS-2009.1, then added back in FMC1278.
  • The frequency range allocated for severity levels was changed subsequently in all three Ford EMC specifications.
  • The most significant differences for Us Vp-p requirements occurred between  ES-XW7T-1A278-AC & EMC-CS-2009.1.


CI 210 Frequency Steps

The most significant differences in frequency steps requirements occurred between  ES-XW7T-1A278-AC & EMC-CS-2009.1.


ES-XW7T-1A278-AC CI 210: Test Setup
  • The test harness connecting the DUT to the Test Fixture and transient pulse generator shall be < 2000 mm in length.
  • The DUT and wire harness shall be placed on an insulated support 50 mm above the ground plane. If the outer case of the DUT is metal and can be grounded when installed in the vehicle, the DUT shall be mounted and electrically connected to the ground plane.

ES-XW7T-1A278-AC CI 210: Test Procedure

  1. Adjust DC offset of the signal generator/audio amplifier to 13.5 volts with the DUT disconnected (open circuit)
  2. At each test frequency set and record the signal generator output to the specified voltage level with the DUT disconnected (open circuit).
  3. Without the test signal present, connect the DUT and verify that it is functioning correctly.
  4. Apply the test signal to the DUT and the Test Fixture such that all power and control circuits are exposed to the disturbance. All power and control circuits are tested simultaneously.
EMC-CS-2009.1 CI 210: Test Setup

  • The test harness connecting the DUT to the Load Simulator and modulated DC supply shall be < 2000 mm in length.
  • All DUT power/power return circuits shall be connected together at the modulated power supply.
  • Per previous versions of this requirement, a ground plane may be placed under the DUT and Load Simulator, but if used, the DUT and wire harness shall be placed on an insulated support 50mm above the ground  plane. Additionally, the negative connection of the modulated DC supply and case of the Load Simulator shall be referenced to the ground plane.


EMC-CS-2009.1 CI 210: Test Procedure

  1. Without the DUT connected, adjust the DC voltage offset "Up" of the modulated power supply to 13.5 volts. Initially set the AC voltage amplitude "Us" to zero volts.
  2. Connect and activate the DUT and verify it is functioning correctly. Verify that Up remains at 13.5 VDC. Adjust the supply as required to achieve this voltage level.
  3. At each test frequency increase Us to the corresponding stress level while the DUT is operating. The dwell time shall be at least 2 seconds. A longer dwell time may be necessary if DUT function response times are expected to be longer. This information shall be documented in the EMC test plan.
FMC1278 CI 210: Test Setup

  • The test harness connecting the DUT to the Load Simulator and modulated DC supply shall be < 2000 mm in length.
  • All DUT power/power return circuits shall be connected together at the modulated power supply.



FMC1278 CI 210: Test Procedure

  1. Without the DUT connected, adjust the DC voltage offset "Up" of the modulated power supply to DUT’s system voltage (13.5, 27 volts). “Us” is initially set to zero volts.
  2. At each test frequency adjust and record the signal generator output required to achieve the specified modulation voltage level “Us” with the DUT disconnected (open circuit). Use the frequency steps listed.
  3. Without the modulation signal present (i.e. Us = 0 volts), connect the DUT and verify it is functioning correctly.
  4. At each test frequency, apply the signal generator levels recorded in step (2) to the DUT and the Load Simulator such that all power and control circuits are exposed to the disturbance. The dwell time shall be at least 2 seconds. A longer dwell time may be necessary if DUT function response times are expected to be longer. This information shall be documented in the EMC test plan and test report.
Fixing EMC-CS-2009.1 CI 210 Us (Vp-p) calibration issue:

CI 210 test waveform is not the superimposed alternating voltage per ISO 16750-2. 
Prior to test Us is calibrated (substitution method) to maintain the required Us V(p-p) while DUT is driving high current loads (e.g. 30A): at each test frequency increase Us to the corresponding stress level while the DUT is operating. The amplifier (e.g. Techron 7796) is configured to operate as Voltage-Controlled Source. Whenever functions are paused between activations (very low current) the amplifier will increase its output voltage in an attempt to drive the requested current into DUT as recorded during Us (Vp-p) calibration. This will result in high voltage (e.g. above 40V) being present for long enough time at DUT VBATT input that can damage components.

The solution is to run CI 210 per FMC1278 that has corrected the test procedure: at each test frequency adjust and record the signal generator output required to achieve the specified modulation voltage level “Us” with the DUT disconnected (open circuit).


Christin Rosu

Shielding Effectiveness

The generic shielding effectiveness requirement is 40 dB for magnetic field, electric field, and plane waves. Depending on the application the frequency range can start from 10 Hz going up to GHz.

To predict shielding effectiveness (SE) of a metal sheet the following factors are summed:  Absorption Loss (A), Reflection Loss (R), re-Reflection Correction Factor (C).  SE = A + R – C (see MIL-HDBK-419A).












Absorption loss depends on material thickness, permeability, electrical conductivity, and the frequency of the incident wave.  It is the same for all electromagnetic waves.

Reflection loss depends on the distance of the EMI source to the material (different for electric, magnetic, and plane waves), material electrical conductivity, and the frequency of the incident wave.

Sources:
Christian Rosu

Automotive BCI Test Limits

The Bulk Current Injection (BCI) test method simulates a field-to-wire coupling from nearby low frequencies radiated fields induced onto a test harness small relative to wavelength.
The coupling from BCI probe will increase with test frequency when the cable is electrically short, and then flatten out when the cable approaches and exceeds a half-wavelength in length.

The transducers (RF current transformers) inject current into both sides of the test harness, therefore both DUT and Load Simulator are subject to test. RF radiation from load simulator cables is possible, but it can be reduced placing 20cm of clip-on split-ferrite RF suppressers close to the transducer.

The BCI common-mode current injected in the test harness simulates an illuminating RF field.
To simulate conducted differential-mode disturbances the BCI induced current is injected in individul conductors.

Using the Substitution Method the actual current injected in test cables can vary from what was initially  calibrated, being less likely to over-test but more real-life representative.

To ensure the repeatability of test results, the cable under test must be centered within BCI current probe, the test set-up must be consistent, especially cable routing, placement of the clamp, and proximity to metal structures.


BCI Calibration Levels per MIL STD 416F CS114:


BCI Probe Insertion Loss per MIL STD 416F CS114:


RF Immunity Ratio mA versus V/m per MIL STD 416F:


Ford RI 112 (BCI) Calibration Limits requirements per FMC1278:



CAN Bus Off Recovery

CAN Bus Off is an error state of the CAN controller and it can be set only by the Transmitter Node when Transmit Error Counter is above 255. Such critical error is usually the result of a critical hardware issue (e.g. high level of electromagnetic field, bus wiring short-circuit, defective transceiver).


Methods to self-recover from a Node CAN Bus Off state:

1) Automatically after the CAN controller generates an interrupt.

2) Manually upon User request (ISO11898-1 §6.15).

In both the above  instances the bus turns back on after 128 occurrences of 11 consecutive Recessive Bits (BOSCH CAN 2.0B §8.12).

Auto-Bus-ON is not required by ISO 11989, therefore the CAN controller makers let the application to decide on its implementation. The automotive industry does not encourage the auto-bus-on feature.

If application's driver reports repeatedly the CAN Bus Off state the application should stop using the CAN.

Christian Rosu


CAN BUS Off Error Handling

CAN Bus Error Handling

Error handling is built into in the CAN protocol. Each node maintains two error counters: the Transmit Error Counter and the Receive Error Counter. Using the error counters, a CAN node can not only detect faults but also perform Error Confinement.

 

CAN Bus Error Detection Mechanisms

1. Bit Monitoring.

2. Bit Stuffing.

3. Frame Check.

4. Acknowledgement Check.

5. Cyclic Redundancy Check.

 

CAN Bus Error Confinement

 

The CAN bus is capable to distinguish between temporary erratic errors and continual erratic errors.

A node starts out in Error Active mode. When any one of the two Error Counters raises above

127, the node will enter a state known as Error Passive and when the Transmit Error Counter raises above 255, the node will enter the Bus Off state.

 

Error Active              node will transmit Active Error Flags when it detects errors.

Error Passive            node will transmit Passive Error Flags when it detects errors.

Bus Off                      node is disabled from transmit/receive operations.

 

Transmit errors give 8 error points

Receive errors give 1 error point

 

Correctly transmitted and/or received messages causes the counter(s) to decrease.

 

Whenever a node tries to transmit a message, if for whatever reason fails it will increases its Transmit Error Counter by 8 and transmits an Active Error Flag. Then it will attempt to retransmit the message, and if it fails will increment by 8 points the Transmit counter. Above 127 (i.e. after 16 attempts), this node goes Error Passive and from this moment it will transmit Passive Error Flags on the bus. A Passive Error Flag will not affect other bus traffic, the other nodes won’t hear the faulty node complaining about bus errors. However, the faulty node continues to increase its Transmit Error Counter and once above 255 it will go into Bus Off.

 

Error state of a node unit

Transmit error counter (TEC)

Receive error counter (REC)

Error active state

0 – 127

AND

0 – 127

Error passive state

128255

OR

128255

Bus off state

Minimum 256

 






For every active error flag that transmitted by a faulty node, the other nodes will increase their Receive Error Counters by 1. By the time that a faulty node goes Bus Off, the other nodes will have their Receive Error Counters below Error Passive limit (127). This count will decrease by one for every correctly received message the faulty node being in Bus off state.

 

 

 

Transmit/receive error counter change conditions

Transmit error counter (TEC)

Receive error counter (REC)

1

When the receive unit has detected an error, except when the receive unit detected a bit error while it was sending an active-error flag or overload flag.

 

 

+1

2

When the receive unit has detected a dominant level in the first bit that it received after sending an error flag.

 

 

+8

3

When the transmit unit has transmitted an error flag 1)

+8

4

When the transmit unit has detected a bit error while sending an active-error flag or overload flag

 

+8

 

5

When the receive unit has detected a bit error while sending an active-error flag or overload flag

 

 

+8

6

When any unit has detected a dominant level in 14 consecutive bits from the beginning of an active-error or an overload flag, and each time the unit has detected a dominant level in 8 consecutive bits thereafter.

 

For a transmit unit

+8

 

For a receive unit

+8

7

When any unit has detected a dominant level in additional 8 consecutive bits after a passive-error flag, and each time the unit has detected a dominant level in 8 consecutive bits thereafter.

 

For a transmit unit

+8

 

For a receive unit

+8

8

When the transmit unit has transmitted a message normally (ACK returned and no errors detected until completion of EOF).

-1

±0 when TEC = 0

 

9

When the receive unit has received a message normally (no errors detected until ACK slot and the unit was able to return ACK normally).

 

 

–1 when 1 REC 127

±0 when REC = 0

When REC > 127, a value between 119 to 127 is set in REC

10

When  the  unit  in  a  bus-off  state  has  detected  a  recessive  level  in  11 consecutive bits 128 times.

Cleared to TEC = 0

Cleared to REC = 0

 

1) The transmit error counter does not change in the following cases:

  •  When the transmit unit while in an error-passive state has detected an ACK error for reasons that ACK was not detected and has detected no dominant levels while sending a passive-error flag.
  • When the transmit unit has encountered a stuffing error during arbitration (dominant level is detected although it transmitted a recessive level as bit stuffing).

 

CAN Bus Failure Modes (ISO 11898)

 

1. CAN_H interrupted (a)

2. CAN_L Interrupted (a)

3. CAN_H shorted to battery voltage (a)

4. CAN_L shorted to ground (a)

5. CAN_H shorted to ground (a)

6. CAN_L shorted to battery voltage (a)

7. CAN_L shorted to CAN_H wire (b)

8. CAN_H and CAN_L interrupted at the same location (c)

9. Loss of connection to termination network (a)

 

Expected behavior:

  • a)     bus survives with a reduced S/N ratio
  • b)     bus survives with a reduced S/N ratio (optional)
  • c)     the resulting subsystem survives

 

Whenever a CAN Tx error count reaches 255, a node will turn bus off and potentially reset itself. A good implementation will not continue resetting a node if the problem persists. In addition to this safety mechanism, ECU's (electric control units) evaluates the duration between valid transmissions of the messages they expect to receive. Therefore, if the engine controller goes offline, nearly every ECU in the vehicle will report "Lost Communication with the Engine Controller." Typically, these type of CAN problems are identified by DTC's (diagnostic trouble codes). Depending on the severity of the issue, the vehicle might enter a "limp home" mode, or might be totally disabled. Limp-home mode is the condition when all the ECUs fail in the car network. A set of default parameters are initialized and your car can continue running only for some time before it is properly serviced by the OEM.

 

A CAN bus node (ECU) automatically goes bus on after 128 x 11 bits, which is the equivalent for 128 messages.

The 11 bits is the recessive time between messages so even in a 100% loaded bus, a bus off node will go bus on again.

 

Accordingly with ISO 11898, “a node can start the recovery from «bus-off» state only upon a user request”; it can be the ECU software or the CAN bus controller, to avoid a complete soft CPU reset. The ability to select between auto-recovery and manual recovery is CAN bus controller implementation defendant.

 

Scenario: Rx channel is damaged on Node 1 and rejects messages from Node 2. As result Node 2 will go buss off, then it auto-recovers, then immediately Node 1 reject messages collapsing the whole communication. The automotive industry does not encourages the auto-bus-on feature.

 

Name

Baud rate

Specification

Application field

SAE J1939-11

250k

Two-wire shielded twisted pair

Truck, bus

SAE J1939-12

250k

Two-wire shielded twisted pair 12 V supply

Agricultural machine

SAE J2284

500k

Two-wire twisted pair (non-shielded)

Automobile

(high-speed: power train system)

SAE J2411

33.3k, 83.3k

One-wire

Automobile (low-speed: body system)

NMEA-2000

62.5k, 125k, 250k, 500k,1M

Two-wire shielded twisted pair Power supply

Ship

DeviceNet

125 k, 250 k, 500 k

Two-wire shielded twisted pair 24 V supply

Industrial equipment

CANopen

10k, 20k, 25k, 50k, 125k

250k, 500k, 800k, 1M

Two-wire twisted pair

Optional (shielded, power supply)

Industrial equipment

SDS

125k, 250k, 500k, 1M

Two-wire shielded twisted pair Optional (power supply)

Industrial equipment

 

Class

Communication speed

Purpose of use

Application range

CAN

Other protocols

Class A

Up to 10 kbps

(body system)

Lamp and light

Power window

Door lock

Power sheet

Keyless entry, etc.

Low-speed

 

 

 

 

 

High-speed

Each carmaker’s

original protocol

LIN

Class B

10 kbps to 125 kbps

(status information system)

Electronic meter

Drive information

Auto air-conditioner

Failure diagnosis, etc.

J1850

VAN

Class C

125 kbps to 1 Mbps

(real time control system)

Engine control

Transmission control

Brake control

Suspension control, etc.

Safe-by-Wire

Class D

5 Mbps and over (multimedia)

Car navi,

Audio

by-Wire, etc.

 

D2B optical

MOST

IEEE 1394

FlexRay


Christian Rosu

IEC 61000-4-4 (Electric Fast Transients / Burst)

A burst arc occurs when a mechanical contact is open during the switching process. Burst sources:
• Circuit Breakers in electrical circuits
• High Voltage switchgear
• 110/230V Power Supply systems
• 24V Control Lines

A burst has a single pulse rise time/duration of 5 ns / 50 ns from a 50 Ohm source impedance.
Bursts of 15 ms duration with a repetition rate of 5 kHz (or 100 kHz) are applied every 300 ms.

Voltage test levels:
• Power ports: 0.5 KV, 1 KV, 2 KV, 4 kV
• Signal and Control ports: 0.25 KV, 0.5 KV, 1 KV, 2 kV

• Coupling method is used to transfer the transient to the DUT.
• Decoupling method is used to block the transient from entering the mains and damaging other equipment connected in the network.

• Power line coupling is done with direct CDNs (Coupling/Decoupling Networks).
• Signal line coupling is done with a CCC (Capacitive Coupling Clamp): two metal plates which sandwich the line under test (cable) to provide a distributed coupling capacitance.

Test waveform verification is mandatory prior to each test.
For equipment connected to power ports all lines are coupled simultaneously.

Christian Rosu

Automotive Cold Crank, Load Dump, and Reverse Polarity Protection

The suppliers of automotive electronic devices are competing these days to lower the cost of theirs designs. This is a sample of rather expensive solution to ensure proper function of an automotive electronic device during transients on supply lines (12V Battery).


Sample of less expensive solution to prevent reverse polarity, load dump, and cranking pulse from disturbing circuits sourced from a 5V voltage regulator or directly from the 12V B+ line.