Power Supply Leakage Current Testing to IEC60990 基于 IEC60990 - 电源的漏电流测试

A customer recently

asked me why we specify leakage current on a Class II power supply, when a

Class II power supply has no ground terminal.

A good question, but first some background.

一位客户*近询问，为什么II类电源并没有接地端子，却要指定II类电源的漏电流。

As part of the

testing for IEC60950, power supply manufacturers measure leakage current

to the IEC60990 standard.

作为 IEC60950 测试的一部分，电源的制造商要根据 IEC60990 标准来测试漏电流。

To be more accurate,

the terms “Touch Current” and “Protective Conductor Current” replace the term

“Leakage Current”.

更加准确的说，“接触电流”和“保护导体电流”这两个术语将取代“漏电流”这一术语。

Protective

Conductor Current (PCC)

保护导体电流 (PCC)

Is the current that

flows through the protective conductor; commonly referred to as the ground

connection.

流过一般称为接地连接的保护导体的电流。

AC Supply 交流电

Protective Conductor Current 保护导体电流

Power Supply 电源

Enclosure 外壳

As a note, the

withstand voltage and insulation resistance tests measure the current flowing

through the insulation of the unit under test.

注意，耐受电压和绝缘电阻测试时会测量流经被测电源绝缘部分的电流。

Touch Current (TC)

接触电流 (TC)

Is the current that

flows when a human body touches the equipment, simulated by a body impedance

network.

人体接触设备时流过的电流，如下示意是由人体阻抗网络进行模拟。

AC Supply 交流电

Isolation Transformer 绝缘变压器

Switches 开关

Power Supply 电源

Enclosure 外壳

Accessible Conductive Part 可触及导电部分

Touch Current 接触电流

Body Impedance Network 人体阻抗网络

The switches are used

to simulate a line, neutral or ground fault, referred to as a single fault

condition (S.F.C.). Usually there is a

polarity reversal switch to reverse the line and neutral connections to the

power supply.

开关用于模拟火线，零线或接地线故障，称为单一故障条件 (S.F.C.)。通常，使用*性反转开关来改变电源上的火线和零线连接。

So back to theoriginal customer question, if a Class II power supply is used, there will be

current that flows through a human body upon touching conductive parts in a

system (like a USB port or a conductive product case). That measured current is usually listed on

the power supply datasheet.

回到客户的问题，如果使用II类电源，在接触系统的导电部分时（例如 USB 端口或产品的导电外壳），电流将流过人体。所测得的电流一般列在电源数据表中。

Here is an excerpt

from a CB report showing the test, input voltage, frequency and the measured

touch current. Note half the tests

conducted were with the simulated human body touching the “output connector” or

pins of the power supply.

这是从CB 测试报告里摘录，输入电压、频率，以及测得的接触电流。请注意，所执行的一半测试使用了模拟的人体来接触“输出连接器”或电源的引脚。

Enclosure leakage current (normal conditions,

normal polarity)

机壳漏电流（正常状态，正常*性）

Enclosure leakage current (normal conditions,

reverse polarity)

机壳漏电流（正常状态，反向*性）

Enclosure leakage current measured on output

connector (normal conditions, normal polarity)

输出连接器上测得的机壳漏电流（正常状态，正常*性）

Enclosure leakage current measured on

output connector (normal conditions, reverse polarity)

输出连接器上测得的机壳漏电流（正常状态，反向*性）

Enclosure leakage current (single fault

conditions, neutral open, normal polarity)

机壳漏电流（单一故障条件，零线开路，正常*性）

Enclosure leakage current (SFC, neutral

open, reverse polarity)

机壳漏电流（单一故障条件，零线开路，反向*性）

Enclosure leakage current measured on

output connector (SFC, neutral open, normal polarity)

输出连接器上测得的机壳漏电流（单一故障条件，零线开路，正常*性）

Enclosure leakage current measured on

output connector (SFC, neutral open, reverse polarity)

输出连接器上测得的机壳漏电流（单一故障条件，零线开路，反向*性）

The ammeter used is a

specialized meter; do not use a regular hand-held multi-meter!

所用的电流表为专用电流表，请勿使用常规的手持式万用表！

For more details,

including the limits of the measured currents, please consult a professional

safety engineer.

有关更多详细信息，包括测得电流*限等内容，请咨询专业安规工程师。

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