Shielded 2-prong AC power cable

[dmusoke]

I just saw an ad for a shielded 2 prong AC power cable and was wondering how the shielding is possible? Where does the shield come from? I am looking for one to place in my rack as i want to minimize 60Hz fields as much as possible. MiddleAtlantic has their SignalSafe power cables that twist the line, neutral, earth wire tightly together.

 

[Speedskater]

An interesting question. Under certain conditions, a shield does not need to be connected to ground to work. But you need to read all the fine print and Henry W. Ott has about 850 pages of fine print.

Henry W. Ott
http://www.hottconsultants.com/

In any case the cable's shield is for very high frequency noise, not for the power line 60Hz field.

For easier reading, see Jim Brown's paper.

http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

 

[dmusoke]

An interesting question. Under certain conditions, a shield does not need to be connected to ground to work. But you need to read all the fine print and Henry W. Ott has about 850 pages of fine print.

Henry W. Ott
http://www.hottconsultants.com/

In any case the cable's shield is for very high frequency noise, not for the power line 60Hz field.

For easier reading, see Jim Brown's paper.

http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf

Thanks Speedskater ... Quite a read!

 

[Speedskater]

Typically shielded power cords are found on PC/computers and components that have Switch Mode Power Supplies (SMPS). Why? Some SMPS's generate a lot of noise and the power cord acts as a transmitting antenna for this interference. So one easy step to help pass the interference tests is to add shielding to the power cord. Many of these components have Class II insulated enclosures that don't require the third Safety Ground wire. Any IEC connector on the component may connect the shield to the chassis, but the other end of the cord may have a two pin plug.

 

[dmusoke]

Typically shielded power cords are found on PC/computers and components that have Switch Mode Power Supplies (SMPS). Why? Some SMPS's generate a lot of noise and the power cord acts as a transmitting antenna for this interference. So one easy step to help pass the interference tests is to add shielding to the power cord. Many of these components have Class II insulated enclosures that don't require the third Safety Ground wire. Any IEC connector on the component may connect the shield to the chassis, but the other end of the cord may have a two pin plug.

Speedskater .... have you been able to find a shielded two pin AC cord? I haven't been able to find any except from MiddleAtlantic who want me to buy a kit of 20 of them. I have no need for 20 cords, i only need about 4 or so. All shielded cords i've seen have been 3-pronged!

 

[Speedskater]

No, but then I'm not in the market for any replacement power cords.

Last year, I measured several IEC power cords in my spares box. Using a very good 6 &1/2 digit Ohm meter (DMM). Some of them had very poor (high resistance) readings.