What is a Class II external power supply?

The use of a Class II external power supply is straightforward, with the main difference compared to a Class I product being that it requires only 2-core main leads for secure operation. Protection is maintained by double or reinforced insulation, rather than relying on both protective earthing and basic insulation.

Does a Class II power supply need a protective earth?

While a Class II power supply does not require a protective earth, some lower power Class II products find applications in Class I systems, and Class II applications often use a functional earth in the system. The Class II supply is designed to meet EMC requirements for emissions and immunity.

What is a Class 2 limited power source (LPs)?

It is important to note the distinction between a Class II power supply and a Class 2 Limited Power Source (LPS), which is a power supply that relates to the volt-amp (VA) rating of the output being limited. VA refers to the level of power in a direct current electric circuit.

Does a Class II power supply have a low impedance path?

The Class II supply is designed to meet EMC requirements for emissions and immunity. However, if the output of the supply is connected to a safety earth or a functional ground, it will create a low impedance path for noise, altering the power supply’s characteristic performance.

How does a Class I power supply work?

Class I power supplies protect the user through at least one layer of basic insulation first. It then uses a ground wire chassis — a grounding connection usually on the casing of the source — that grounds the hazardous voltage before it reaches the user should the basic insulation fail.

What is the difference between a Class 1 power supply and VA?

VA refers to the level of power in a direct current electric circuit. Class I power supplies protect the user through at least one layer of basic insulation first.