What is EMC?

EMC stands for Electromagnetic Compatibility, which means that a device is compatible with (i.e. no interference is caused by) its electromagnetic (EM) environment. Does not emit levels of EM energy that generate electromagnetic interference (EMI) to other devices in the vicinity.

Electromagnetic interference (EMI) is interference caused by one electrical or electronic device to another by the electromagnetic fields created by its operation.

Sometimes we notice that the tube light blinks when a water pump or motorized device is on. This is because the motor draws more current, which causes a voltage drop. The change in electrical current and voltage generates electromagnetic interference (EMI). This interference must be within specific limits to avoid interference with other devices present within range.

An EMC test identifies this electromagnetic interference generated by a device. EMC tests also determine how the device reacts to electromagnetic interference caused by another device.

All devices have the potential to emit electromagnetic fields. Devices used in our daily lives, such as TVs, cell phones, washing machines, ATMs, RFID tags, etc., generate electromagnetic interference or can be damaged by interference generated by another device. To ensure the smooth functioning of devices, an EMC test performs several subtests on the equipment under test (EUT) to test the immunity of the victim device to survive in an electromagnetic emission environment. Furthermore, the EMI generated by the EUT must be within the interference limit regulated by the country.

Types of EMC Tests
The basic block diagram of EMC tests is given below. Not all of these are not applicable to each product, and other testing will likely be added according to the product application.

EMC tests consist of two tests – one is EMI (Electromagnetic Interference) and the other is EMS (Electromagnetic Susceptibility).

Electromagnetic Interference (EMI)
An electronic device will generate current and voltage fluctuations, which produce electromagnetic interference (EMI). Therefore, the EMI generated by a specific device needs to be limited by proper electronic design and shielding so as not to affect neighboring devices.

For example, a drill running in the house can cause flickering on the TV in the neighborhood house because they are connected to the same supply line.

Types of Electromagnetic Interference (EMI)

• Conducted Emission

When the device emits an electromagnetic field and transmits it from the conductor of a wire, it is called conducted emission. It can potentially cause problems throughout the power distribution network, affecting other devices.

• Radiated Emission

When the device emits electromagnetic energy, it is released in the form of electromagnetic fields that propagate through the air and can also interfere with other nearby devices.

• Voltage flicker emission

Voltage oscillation occurs due to changes in the load current, which oscillates in both frequency and amplitude. This can be illustrated by the change in brightness of a light bulb or the change in motor or fan speed.

• Harmonic Current Emission

When the device emits any harmonics and distorts the mains supply, it is called harmonic current emission. It is associated with switched-mode power converters and other nonlinear loads such as motors, transformers, and lamp dimmers.

Electromagnetic Susceptibility (EMS)
Electromagnetic Susceptibility (EMI) means that the device is capable of or has the immunity to survive or function as expected in an environment where other devices generate electromagnetic interference. Every device tends to emit electromagnetic interference, so the victim device must not misbehave in these environments; all of this is noted in the country's EMS testing standards.

Let's take a real-life example to understand why EMS testing is necessary. If a user hears noise on their cell phone while another cell phone or appliance is in use, it is due to the device's low immunity.

Types of Electromagnetic Susceptibility (EMS)

• Driven immunity

In the immunity test performed, the disturbance in the cable or power supply is created by an RF amplifier, and the operation of the device must not be affected by this distortion or interference in the power supply.

• Irradiated immunity

In a radiated immunity test, the device creates an electrical field disturbance, noise, or magnetic field interference through the air. In this scenario, the device should function as expected.

• Electrostatic Discharge (ESD)

Electrostatic Discharge is the Discharge of the human body on the metal part of the device; Whenever the human body touches the device, they will get a shock. It could permanently damage the device, so this test will verify protection and immunity against ESD.

• Electrical Fast Transient (EFT)

The EFT immunity test simulates real-world switching of inductive loads. Inductive load switching creates a small spark, which is a burst of pulses. The device must be able to handle these pulses.

• Outbreak

ESD and EFT have similar rise times, pulse widths, and energy levels. With a surge, the pulse rise time is only 1.2us and the duration is longer. The pulse width is 50us, so there must be protection in the circuit to deal with the surge.

• Magnetic field

The magnetic field is everywhere; a current passing through a wire can generate a magnetic field around the wire. In this test, the magnetic field is created to test the behavior of the device and the functionality of the device should not be affected.

• Voltage drop and short interruption

In this test, power supply fluctuations are created in AC or DC and then the device is observed under these conditions.

Global rules and regulations
The EMC standard is different for each country. The Federal Communication Commission (FCC) has some regulations and standards for EMC certification in the US. In Canada, Industry Canada is equivalent to the FCC. In Europe, the CE mark is equivalent to the FCC.

Some of the brands provided by these regulatory bodies are as follows: