Power supply leakage current test based on IEC60990

As part of the IEC60950 test, power supply manufacturers test leakage current according to the IEC60990 standard.

To be more precise, the terms "touch current" and "protective conductor current" will replace the term "leakage current".

Protective Conductor Current (PCC)

The current flowing through the protective conductor generally known as the earth connection.

Graphics:
AC Supply
Protective Conductor Current
Power Supply
Enclosure

Note that the withstand voltage and insulation resistance tests measure the current flowing through the insulation of the power supply under test.

Contact current (TC)

The current that flows when the human body touches the device is simulated by the human body impedance network as shown below.

Switches are used to simulate a live, neutral, or ground fault, known as a single fault condition (SFC). Typically, a polarity reversal switch is used to change the live and neutral connections on the power supply.

Back to the customer's question, if a Class II power supply is used, current will flow through the human body when touching a conductive part of the system (such as a USB port or the conductive housing of the product). The measured current is generally listed in the power supply data sheet.

This is an excerpt from the CB test report, the input voltage, frequency, and measured touch current. Note that half of the tests performed used a simulated human body to touch the "output connector" or pins of the power supply.

Graphics and Text:
AC Supply
Isolation Transformer
Switches
Power Supply
Enclosure
Accessible Conductive Part
Touch Current
Body Impedance Network

Caption:
Enclosure leakage current (normal conditions, normal polarity)
Enclosure leakage current (normal conditions, reverse
polarity) Enclosure leakage current measured on output connector ( normal conditions, normal polarity) Enclosure leakage current measured on output connector (normal conditions, reverse polarity) Enclosure leakage current (single fault conditions, neutral open, normal polarity) Enclosure leakage current (SFC, neutral open, reverse polarity) Enclosure leakage current measured on output connector (SFC, neutral open, normal polarity) Enclosure leakage current measured on output connector (SFC , neutral open , Chassis leakage current measured at the output connector (single fault condition, open neutral, reverse polarity )

The ammeter used is a special ammeter, please do not use a regular handheld multimeter!

For more detailed information, including measured current limits, please consult a professional safety engineer.