EMC testing is a process of evaluating an electrical & electronic product's ability to function as intended in the presence of electromagnetic fields and to ensure that it does not generate harmful electromagnetic emissions. The goal of EMC testing is to verify that the product meets EMC industry standards for electromagnetic compatibility (EMC).

Fig: EMC Chamber

Electromagnetic Compatibility (EMC) is the capability/ability of an electrical & electronic product to withstand a specified degree of electromagnetic disturbance (EMI) from the nearby electronic device(s) and not emit more than a specified amount of electromagnetic interference (EMI). 

An electrical and electronic product can get into to market when it meets the requirements of EMC emission and immunity standards. The EMC emission measurement standards ensure the product does not emit more than a specified level of EMI. The EMC emission measurement standards specify the EMI emission limit for products and EMI emission measurement procedures. The EMC immunity standards ensure that the product can withstand EMI from nearby devices and operate properly. The EMC immunity standards specify the test procedure, test setup, test levels, and so on.  

EMC testing evaluates whether the product meets the requirements of EMC emission and immunity standards. When a product meets the requirements of these EMC standards, the product is said to be EMC compatible/EMC certified product (i.e., withstand EMI from nearby devices & operate properly, and not emit more than a specified level of EMI) and can sell in the market. 

EMC testing typically involves two types of tests: emissions measurement test and immunity test. An emissions measurement test is used to measure the amount of EMI emitted by a device, while immunity testing is used to measure the device's ability to withstand EMI from external sources. The EMC testing is performed as per EMC standards typically in a laboratory setting using specialized equipment, such as an EMC test chamber. Some EMC testing is performed in open-area test sites (OATS). 

Why is EMC testing important?

Electrical & electronic equipment is often subjected to electromagnetic interference (EMI) from various sources, such as power lines and other nearby electronic devices in the same working environment. If a product is not properly tested for EMC, it could experience performance degradation, malfunctions, or complete failure when exposed to these types of EMI sources. In addition, the product that generates harmful electromagnetic emissions can interfere with other electronic devices and potentially cause damage or malfunctions.

Hence, EMC testing is necessary to ensure the product does not emit more than the electromagnetic energy emission limit specified in the EMC standards and ensure the product can withstand EMI from other sources that will occur while working in the intended real-time environment. 

How is EMC testing performed on an electrical and electronic product?

As we know that the EMC testing process involves determining the product's susceptibility/immunity to EMI and measuring the levels of electromagnetic emissions it produces. EMC testing involves electromagnetic energy emission levels measurement tests and immunity tests. 

EMC Emission measurements tests: 

Several different types of EMC emission measurement tests may be performed on electrical and electronic equipment, including:

Radiated emission (RE) measurement test: 

This test measures the radiated electromagnetic energy the product emits while working. This test ensures that the product does not emit more than the radiated EMI emission limit specified in the EMC standards. 

Conducted emission (CE) measurement test: 

This test measures the levels of conducted EMI emitted by the product while working. The CE test ensures that the product does not emit more than the conducted EMI emission limit specified in the EMC standards. 

Conducted EMI is unwanted electromagnetic emissions (EMI) from devices while working that propagate through the power cord or power line and may affect the other connected devices on the same line.

Harmonic emission measurement test: 

This test measures the harmonic currents injected into the public power supply by the product while working. This test ensures that the product does not emit more than the harmonic current emission limit specified in the EMC standards. 

Voltage Fluctuation and Flicker test: This test ensures that the product connected to the shared AC mains will not cause voltage fluctuations and flicker on the public low-voltage system. 

In addition to the above measurement tests, harmonics, flicker, and clicks are also measured for a product. 

EMC immunity tests:

Several different types of EMC immunity tests may be performed on electrical and electronic equipment, including:

Radiated immunity (RI) test: This test is conducted to determine the ability of a device/product to withstand radiated EMI.

In this test, the device's immunity to radiated EMI is tested by intentionally applying a significant level of radiated EM field energy (test signals). This immunity test ensures that the product can withstand the radiated EMI from other electromagnetic sources, such as power lines & other electronic devices that the device will encounter while in normal usage.

Conducted immunity test: This test is conducted to determine the ability of a device/product to withstand conducted EMI that are conducted through power lines or other cables. 

In this test, the device's immunity to conducted EMI is tested by intentionally applying a significant level of test signals via cable into the equipment under test (EUT).  This immunity test ensures that the product can withstand the conducted EMI from other electromagnetic sources, such as power lines & other electronic devices that the device will encounter while in normal usage. 

Magnetic field testing:  This test is performed to determine the ability of a device/product to withstand the power frequency (50/60 Hz) magnetic field. The power frequency magnetic field is produced by power lines, transformers, motors, and other electrical devices that operate at 50 or 60 Hz. This immunity test ensures that the product can withstand the magnetic fields from other electromagnetic sources, such as power lines & other electrical devices that the product will encounter while in normal real-time usage.  

Electrostatic discharge (ESD) testing: This test is performed to determine the ability of a device/product to withstand electrostatic discharge (ESD). ESD is a phenomenon that occurs when two objects with different electrical potentials come into contact/very close to each other, causing sudden and momentary electric current flows between the two objects. For example, ESD can occur when the person handling printed circuit boards or troubleshooting electronic devices without using an electrostatic wrist strap. This immunity test ensures that the product can withstand ESD that the product will encounter while in normal real-time usage.   

Surge test: Tests the product's ability to withstand the surge (surge voltage and current).  Surge is a transient overvoltage (short-time overvoltage) in an AC power system that occurs due to the events such as load switching, capacitor bank switching, device faults, and lightning discharges. This immunity test ensures that the product can withstand the surge that the product will encounter while in normal real-time usage. 

Voltage dip test:  This test is performed to determine the ability of a device/product to withstand voltage dip. The voltage dip is the short duration temporary voltage magnitude drop in the main supply voltage of the electrical distribution system or supply system. This immunity test ensures that the product can withstand the voltage dip phenomenon that the product will encounter while in normal real-time usage. 

Electrical Fast Transients and bursts:  Tests the product's ability to withstand the electrical fast transients and bursts.  

Once the testing is complete, the results are analyzed to determine if the product meets the required EMC standards and specifications. If the product does not meet the standards, the manufacturer may need to make changes or modifications to improve its EMC performance.

Non-compliance with EMC standards can lead to malfunctions or failures of electronic products, which can cause serious harm to people or equipment. It can also lead to legal or regulatory penalties, product recalls, and damage to brand reputation. EMC testing ensures the product complies with EMC standards. 

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