GB/T 38659.1-2020 English PDF (GB/T38659.1-2020)

GB/T 38659.1-2020: Electromagnetic Compatibility - Risk Assessment - Part 1: Electronic and Electrical Device
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GB/T 38659.1-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 33.100
L 06
Electromagnetic Compatibility - Risk Assessment -
Part 1: Electronic and Electrical Device
ISSUED ON: MARCH 31, 2020
IMPLEMENTED ON: OCTOBER 1, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Terms and Definitions ... 5 
4 Overview ... 8 
5 Objective of EMC Risk Assessment ... 9 
6 Mechanism and Model of EMC Risk Assessment ... 9 
7 Influence Level of Risk Elements and Risk Classification ... 28 
8 Risk Assessment Unit Division ... 33 
9 EMC Risk Assessment Procedures ... 34 
10 EMC Risk Identification ... 36 
11 EMC Risk Analysis ... 39 
12 EMC Risk Assessment ... 57 
13 Determination and Result Application of Complete-machine EMC Risk Level
... 60 
14 Requirements for Risk Assessment Report ... 62 
Appendix A (informative) Example of Electromagnetic Compatibility Risk
Assessment ... 63 
Appendix B (informative) Example of Attribute Division of Schematic Circuit
Diagram ... 70 
Bibliography ... 71 
Electromagnetic Compatibility - Risk Assessment -
Part 1: Electronic and Electrical Device
1 Scope
This Part of GB/T 38659 provides an overview, objective, mechanism and model of
electromagnetic compatibility (EMC) risk assessment for electronic and electrical
devices, as well as the influence level of risk elements and risk classification, product
risk assessment unit division, EMC risk assessment procedures, EMC risk
identification, EMC risk analysis, EMC risk assessment, complete-machine EMC risk
level determination and result application, and requirements for risk assessment report.
This Part is applicable to electromagnetic compatibility risk assessment of electronic
and electrical devices.
This Part combines factors, such as: product’s mechanical architecture design, circuit
board design and type of application site, to provide guidance for the risk assessment
of product’s electromagnetic compatibility design.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 4365 Electrotechnical Terminology - Electromagnetic Compatibility
GB 4943.1-2011 Information Technology Equipment - Safety - Part 1: General
Requirements
GB/T 6113.201-2018 Specification for Radio Disturbance and Immunity Measuring
Apparatus and Methods - Part 2-1: Methods of Measurement of Disturbances and
Immunity - Conducted Disturbance Measurements
GB/Z 18039.1-2019 Electromagnetic Compatibility - Environment - Description and
Classification of Electromagnetic Environments
GB/T 18655-2018 Vehicles, Boats and Internal Combustion Engines - Radio
Disturbance Characteristics - Limits and Methods of Measurement for the Protection
of On-board Receivers
GB/T 23694 Risk Management - Vocabulary
GB/Z 37150 Guide of Risk Assessment of EMC Reliability
3 Terms and Definitions
What is defined in GB/T 4365, GB/T 23694 and GB/Z 37150, and the following terms
and definitions are applicable to this document.
3.1 Electromagnetic Compatibility Risk
Electromagnetic compatibility risk refers to the probability of electromagnetic
compatibility problems caused by product design. In the test environment, it is the
probability of failing the electromagnetic compatibility test.
3.2 Risk Assessment Value
Risk assessment value refers to the value obtained by qualitative and quantitative
methods and used to express the magnitude of risks. It is usually between 0 ~ 100.
3.3 Electronic and Electrical Equipment
Electronic and electrical equipment refers to equipment manufactured by electronic
technology and that relies on electric current or electromagnetic field to work normally,
and equipment that can generate, transmit and measure current and electromagnetic
field.
NOTE 1: the design AC voltage of the equipment does not exceed 1,000 V; the design DC
voltage does not exceed 1,500 V.
NOTE 2: in accordance with the CISPR product classification, the following equipment
belongs to electronic and electrical equipment: engineering medical equipment,
multi-media equipment, household appliances, automotive electronic
components, etc.
3.4 Common-mode Current
Common-mode current refers to the vector sum of currents on two or more wires
passing through a specified “geometric” cross section.
[GB/T 6113.201-2018, Definition 3.1.14]
3.5 Common-mode Interference
Common-mode interference refers to electromagnetic interference (in the same
direction) caused by the common-mode voltage of the interference voltage on the
signal line and its return line (generally known as signal ground line).
electric conductors, such as: wires, coils and casings, and among certain components.
NOTE: although its value is small, it is an important cause for common-mode interference.
3.12 High-speed Signal
For digital signal, high-speed signal is determined by the edge speed of the signal.
Generally speaking, the signal rise / fall time is less than 4 times the signal transmission
delay.
3.13 “Dirty” Signal / Electrical Circuit
“Dirty” signal / electrical circuit refers to signal / electrical circuit that contains signals
or parts and components that are easily injected by external interference or generate
electromagnetic emissions.
NOTE: for example, signal lines and parts and components that are interconnected with
input and output (I/O) cables and are in front of the filter circuit; signal lines of
electrostatic discharge (ESD) breakdown discharge that are applied to the surface
of the product shell.
3.14 “Clean” Signal / Electrical Circuit
“Clean” signal / electrical circuit refers to signal / electrical circuit that contains signals
or parts and components that are neither susceptible to interference nor generate
significant electromagnetic interference (EMI) noise.
3.15 Special Signal / Electrical Circuit
Special signal / electrical circuit refers to signal / electrical circuit that contains signals
or parts and components that require special processing due to EMC performance.
NOTE: it is divided into special noise signal / electrical circuit and special sensitive signal
/ electrical circuit.
3.16 Noise Signal / Electrical Circuit
Noise signal / electrical circuit refers to signal / electrical circuit that contains signals or
parts and components that would easily generate electromagnetic emission
disturbance in the field of electromagnetic compatibility.
NOTE: for example, clock signal line, pulse width modulation (PWM) signal line and crystal
oscillator, etc.
3.17 Sensitive Signal / Electrical Circuit
Sensitive signal / electrical circuit refers to signal / electrical circuit that contains signals
and parts and components that are susceptible to electromagnetic interference in the
The 19 main EMC risk elements are provided, which may be used as the key elements
in the implementation of product testing and certification to determine whether EMC
testing and assessment needs to be re-conducted after a change of product design.
5 Objective of EMC Risk Assessment
The main objective of EMC risk assessment of electronic and electrical equipment
includes:
---Recognize EMC risks in product design and their potential impact on the
objective;
---Reinforce the understanding of the relevant elements of EMC risks, so as to
facilitate the correct selection of risk response strategies;
---Identify the main factors that lead to EMC risks, as well as the weak links of
EMC design of electronic and electrical equipment;
---Facilitate the determination of whether EMC risks are acceptable; provide
decision makers with quantifiable and relevant information;
---Predict the pass rate of EMC test.
A successful EMC risk assessment of electronic and electrical equipment depends on
thorough understanding of design information of the product being assessed and
relevant risk elements.
6 Mechanism and Model of EMC Risk Assessment
6.1 Mechanism and Ideal Model of EMC Risk Assessment of Mechanical
Architecture
6.1.1 Mechanism of EMC risk assessment of mechanical architecture
Product’s EMC risks include two parts: electromagnetic sensitivity (EMS) and
electromagnetic interference (EMI). Specifically speaking, for EMS, its risk assessment
mechanism is that when a certain port of the product injects the same magnitude of
high-frequency common-mode voltage or the same magnitude of common-mode
current, different product design schemes will have different magnitudes of common-
mode current flowing through the corresponding circuit structure of the PCB. In the
mechanical architecture design, the factors that affect the magnitude of the common-
mode current are the EMS risk elements of the product’s mechanical architecture.
For EMI, its risk assessment mechanism is that when the product is in normal working
condition, due to the signal transmission inside the product, the internal useful signal
A---the relative position of the cable connector in the circuit board;
B---the overlap joint of the shielding layer of the shielded cable;
C---filtering and protection of the power supply and signal input ports outside the PCB;
D---the interconnection between the “0 V” ground plane of the PCB board and metal shell (when
there is an interconnection);
E---the interconnection of “0 V” ground plane among different PCB boards (usually
implemented through structural parts);
F---filtering, protection and signal frequency of the internal PCB interconnection signal port of
the product;
G---the mode of overlap joint among the various metal parts in the shell (taking the impedance
and gap treatment into consideration);
H---the area of loop formed by cables, connectors, PCB (if possible), the interconnection
between “0 V” ground plane of the PCB board and the metal shell, and the product’s metal
shell after entering the shell;
I---shell grounding wire.
NOTE: A ~ I are EMC risk elements of product’s mechanical architecture.
Figure 1 -- EMC Ideal Model of Mechanical Architecture
6.1.3 Requirements for risk elements in EMC ideal model of mechanical
architecture
The risk elements in EMC ideal model of product’s mechanical architecture shall satisfy
the following relevant requirements of ideal model:
---A: the relative position of the cable connector in the circuit board
In the ideal model, the connection position of the cable on the circuit board
shall be placed on the same side of a circuit board.
---B: the overlap joint of the shielding layer of the shielded cable
In the ideal model, the cable has a shielding layer, and the connection of the
shielding layer needs to satisfy the following requirements:
 For metal shell products, the cable shielding layer shall be connected to
the product’s metal shell or metal connector shell at the connector entrance,
and form a 360° overlap;
 For floating products, the cable shielding layer shall form a 360° overlap
with the “0 V” ground plane in the PCB.
---C: filtering and protection of the power supply and signal input port outside the
---F: filtering, protection and signal frequency of the internal PCB interconnection
signal port
The requirements for filtering, protection and signal frequency are as follows:
 F1: in EMS correlation ideal model, the filtering and protection of the
PCB interconnection signal ports inside the product
In the ideal model, the signal in all interconnection connectors shall
receive the filtering treatment.
 F2: in EMI correlation ideal model, the frequency of the PCB
interconnection signals inside the product
In the ideal model, there shall be no high-speed signals, for example,
clock signals or PWM signals in the interconnection signals among the
PCB boards.
---G: the mode of overlap joint among the various metal components of the shell
(taking the impedance and gap treatment into consideration)
In the ideal model, the product shell is a perfect shield. In order to implement
a perfect shield, then:
 Implement an intentional overlap among the various metal surfaces of
the shielding body, and;
 The aspect ratio of each metal body in the shielding body in the
interconnection direction is less than 5, and;
 The maximum size of the gap or the aperture between the overlap points
cannot exceed the minimum size in the following two circumstances:
1) 1/100 of the wavelength of the highest frequency of the circuit;
2) 15 mm.
NOTE 2: intentional overlap refers to the overlap specially designed for EMC
objective, such as: screw fastening, welding, riveting, clamping and
connection implemented by filled conductive materials, etc.
---H: the area of loop formed by cables, connectors, PCB (if possible), the
interconnection between “0 V” ground plane of the PCB board and the metal
shell, and the product’s metal shell after entering the shell
The loop area is shown in Figure 2. The larger the loop area, the larger the
parasitic inductance. The larger inductance will hinder the discharge of
interference current.
3---“clean” signal / electrical circuit area;
4---special signal / electrical circuit area (including internal noise signal / electrical
circuit area, sensitive signal / electrical circuit area);
5---ground plane.
Figure 7 -- Schematic Diagram of Construction of EMC Ideal Model of PCB
In order to implement the ideal model shown in Figure 7, PCB needs to be performed
from two parts: schematic circuit diagram and PCB layout. The implementation of the
ideal model of the schematic circuit diagram is established on the attribute division of
the schematic circuit diagram. In accordance with the requirements of Figure 7, if the