Understanding the different classes of power supply protection is not just necessary but essential, given the variety of electrical devices we use daily. In this guideline, We will explain the electronic protection classes of the power supply and offer you a detailed analysis of their differences, features, and suitable applications.
Summary of Power Supply Protection Classes
Based on the need (or not) for a protective earth connection, The International Electrotechnical Commission (IEC) has set out three safety classes for power supplies: Class I, Class II, and Class III. There are some critical points for them.
Class I – where user protection from the electric shock is ensured through a mix of insulation and protective earthing/grounding.
Class II – where user protection from electric shock is secured through double or reinforced insulation, eliminating the need for earthing or grounding.
Class III – Where the input is linked to a Safety Extra-Low Voltage (SELV) circuit, additional protective measures like earthing or grounding are not required.
Class I Protection
Regarding the Class I protection, devices are grounded, meaning they have a direct physical connection to the earth. Grounding isn’t a simplistic feature; it’s a well-calculated safety measure. The device’s metal casing is linked to the ground, establishing a low-resistance path for electric current to flow away from the user.
If a fault occurs, the current takes the path of least resistance, i.e., the grounding wire, and protects the user from electric shock.
Class I devices are prevalent in environments requiring strong durability and robust safeguards against electrical faults. These devices are commonly found in industrial settings.
Here is the list of class I electrical appliances:
- Industrial Equipment such as Machinery, motors, and heavy-duty tools.
- Medical equipment such as imaging machines, surgical instruments, and patient monitoring systems；
- Household appliances like refrigerators, washing machines, and ovens;
- Automotive components, like electric vehicle chargers or power distribution units；
- Industrial Controls: Control panels, PLCs, and automation systems benefit from Class I power supplies to maintain operational stability.
Class II Protection
Insulation is using plastic as an isolation barrier due to its low conductivity of electricity. This ensures the current remains confined to its designated circuit, stopping any electrical leak without necessitating a ground connection. Class II power adapters utilize a concept known as “double insulation.” which works via 2-core main leads instead of earth connection for safe operation.
It is essential to adhere to the specified minimum distance between any live part and the enclosure, whether it is conductive. This practice ensures the maintenance of the two layers of protection necessary to guard against a potential single failure within the system.
This double insulation works as a fail-safe, ensuring that even if the first layer gets compromised, the second layer steps in as a knight in shining armor.
Here is a list of class II electrical appliances:
- Consumer Electronics devices such as smartphones, tablets, laptops, and gaming consoles often use Class II power supplies due to their compact size and portability.
- Audio Equipment: Amplifiers, speakers, headphones, and audio interfaces can benefit from Class II power supplies in various audio setups.
- Networking equipment like routers, switches, and access points may use Class II power supplies for efficient and reliable network connectivity.
- Medical instruments, like portable diagnostic tools or monitoring devices, and Small household appliances like coffee makers, toasters, and blenders.
- Personal Care Devices such as Electric shavers, toothbrush chargers, and hair dryers
Class III Protection
In Class III equipment, the power source is not dangerous. It is operated at voltages usually lower than 50V. This low voltage minimizes the risk of electrical shock so much that additional safety features like grounding or double insulation often become redundant.
This classification is outlined in IEC62368-1 under the section titled “Classes of equipment concerning protection from electric shock.”
List of class III electrical appliances:
Class 3 electrical appliances operate on a Safety Extra-Low Voltage (SELV) circuit, meaning they are inherently safe and do not require additional protective measures like earthing or insulation. These appliances are often battery-operated or use an external power supply that converts mains voltage to a safe, low voltage. Here’s a list of some common Class 3 electrical appliances:
- Battery-Operated Toys: Toys that run on batteries are usually Class 3 appliances as they operate on low voltage.
- Electric Toothbrushes: These often operate on a low voltage and are charged via a SELV charger.
- Portable Audio Devices: Devices like MP3 players and some Bluetooth speakers that operate on batteries or low-voltage chargers.
- Smartphones and Tablets: While the chargers may not be Class 3, the devices often operate on the low voltage their batteries provide.
- LED Lights: Some LED lights operate on low voltage and are considered Class 3.
Conclusion
Whether you require Class I or Class II protection for your electronic equipment, collaborate with the experts at StablePSU to discover the ideal solution. We provide a range of power supplies tailored to fulfill your grounding and isolation requirements.
