What are the Differences Between IEC Power Supply Protection Classes?

Introduction

The International Electrotechnical Commission (IEC) has outlined three safety classes: Class I, Class II, and Class III. These three classes are in place to protect and prevent a user from hazardous voltages from the input source when using a power supply.

1. Class I – User Protection is achieved from electric shock due to a layer of basic insulation and a grounded conductive chassis
2. Class II – User Protection is achieved from electric shock due to double insulation (basic + supplemental) or reinforced insulation
3. Class III – User Protection is not required as the input voltage is not hazardous

Class I Power Supplies

IEC Class I power supplies have at least a basic layer of insulation and a grounded conductive chassis which protects a user from hazardous input voltage. Basic insulation is the first level of safety. If this was to fail, then this is where the grounded conductive chassis would come in. The hazardous voltage would be grounded by the chassis conductive before any harm happens to the user, i.e. before the hazardous voltage comes into contact with the user!

Class II Power Supplies

IEC Class II power supplies have a basic layer of insulation, however unlike Class I, the power supply is not required to have the Chassis conductive, this is because the PSU also contains a basic & layer of supplemental insulation or a layer of reinforced insulation on its own. The Basic layer acts as the first level of safety protection, whilst the second layer of protection is provided by the layer of supplemental insulation.

Class III Power Supplies

The Input voltage is not at a hazardous level meaning the user does not need protection from the input voltage. “Safety Extra Low Voltage” or SELV for short, is the label that the IEC use for non-hazardous products.  The circuits shall not exceed 60V DC for no longer than 200ms in normal operation, with a limit of 120V DC for a maximum of 20ms. SELV circuits must be separated form hazardous voltages by two levels of protection. This can include a basic layer and supplemental insulation, reinforced insulation, or a basic insulation combined with a safety grounded electrically conductive chassis.

If you require more information regarding the three IEC Power Supply Protection Classes, or need help with finding the right power supply for your project. Please do not hesitate to contact us.

Click here to contact us today!