Power Supply Leakage Current Testing to IEC60990 基于 IEC60990 - 電源的漏電流測(cè)試

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.

一位客戶最近詢問(wèn)，為什么II類電源并沒(méi)有接地端子，卻要指定II類電源的漏電流。

As part of the

testing for IEC60950, power supply manufacturers measure leakage current

to the IEC60990 standard.

作為 IEC60950 測(cè)試的一部分，電源的制造商要根據(jù) IEC60990 標(biāo)準(zhǔn)來(lái)測(cè)試漏電流。

To be more accurate,

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

“Leakage Current”.

更加準(zhǔn)確的說(shuō)，“接觸電流”和“保護(hù)導(dǎo)體電流”這兩個(gè)術(shù)語(yǔ)將取代“漏電流”這一術(shù)語(yǔ)。

Protective

Conductor Current (PCC)

保護(hù)導(dǎo)體電流 (PCC)

Is the current that

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

connection.

流過(guò)一般稱為接地連接的保護(hù)導(dǎo)體的電流。

AC Supply 交流電

Protective Conductor Current 保護(hù)導(dǎo)體電流

Power Supply 電源

Enclosure 外殼

As a note, the

withstand voltage and insulation resistance tests measure the current flowing

through the insulation of the unit under test.

注意，耐受電壓和絕緣電阻測(cè)試時(shí)會(huì)測(cè)量流經(jīng)被測(cè)電源絕緣部分的電流。

Touch Current (TC)

接觸電流 (TC)

Is the current that

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

network.

人體接觸設(shè)備時(shí)流過(guò)的電流，如下示意是由人體阻抗網(wǎng)絡(luò)進(jìn)行模擬。

AC Supply 交流電

Isolation Transformer 絕緣變壓器

Switches 開(kāi)關(guān)

Power Supply 電源

Enclosure 外殼

Accessible Conductive Part 可觸及導(dǎo)電部分

Touch Current 接觸電流

Body Impedance Network 人體阻抗網(wǎng)絡(luò)

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.

開(kāi)關(guān)用于模擬火線，零線或接地線故障，稱為單一故障條件 (S.F.C.)。通常，使用極性反轉(zhuǎn)開(kāi)關(guān)來(lái)改變電源上的火線和零線連接。

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.

回到客戶的問(wèn)題，如果使用II類電源，在接觸系統(tǒng)的導(dǎo)電部分時(shí)（例如 USB 端口或產(chǎn)品的導(dǎo)電外殼），電流將流過(guò)人體。所測(cè)得的電流一般列在電源數(shù)據(jù)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.

這是從CB 測(cè)試報(bào)告里摘錄，輸入電壓、頻率，以及測(cè)得的接觸電流。請(qǐng)注意，所執(zhí)行的一半測(cè)試使用了模擬的人體來(lái)接觸“輸出連接器”或電源的引腳。

Enclosure leakage current (normal conditions,

normal polarity)

機(jī)殼漏電流（正常狀態(tài)，正常極性）

Enclosure leakage current (normal conditions,

reverse polarity)

機(jī)殼漏電流（正常狀態(tài)，反向極性）

Enclosure leakage current measured on output

connector (normal conditions, normal polarity)

輸出連接器上測(cè)得的機(jī)殼漏電流（正常狀態(tài)，正常極性）

Enclosure leakage current measured on

output connector (normal conditions, reverse polarity)

輸出連接器上測(cè)得的機(jī)殼漏電流（正常狀態(tài)，反向極性）

Enclosure leakage current (single fault

conditions, neutral open, normal polarity)

機(jī)殼漏電流（單一故障條件，零線開(kāi)路，正常極性）

Enclosure leakage current (SFC, neutral

open, reverse polarity)

機(jī)殼漏電流（單一故障條件，零線開(kāi)路，反向極性）

Enclosure leakage current measured on

output connector (SFC, neutral open, normal polarity)

輸出連接器上測(cè)得的機(jī)殼漏電流（單一故障條件，零線開(kāi)路，正常極性）

Enclosure leakage current measured on

output connector (SFC, neutral open, reverse polarity)

輸出連接器上測(cè)得的機(jī)殼漏電流（單一故障條件，零線開(kāi)路，反向極性）

The ammeter used is a

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

所用的電流表為專用電流表，請(qǐng)勿使用常規(guī)的手持式萬(wàn)用表！

For more details,

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

safety engineer.

有關(guān)更多詳細(xì)信息，包括測(cè)得電流極限等內(nèi)容，請(qǐng)咨詢專業(yè)安規(guī)工程師。

(link to medical

brochure)