Instrument to inject noise on mains

[Scarr]

Hi,

Does anyone know of some test equipment that I can inject noise (ideally configurable) onto the mains with?

Thanks

Steve

 

[RadioRon]

There is an item called a Line Impedance Stabilization Network that is used to measure power line noise coming out of a piece of equipment, but it would not do exactly what you want, I think. However, studying LISN designs or talking to those who make these things might give you an answer.

 

[crutschow]

You need an injection circuit at the mains input to your equipment. That typically consists of an inductor in series with each line that can carry the equipment current and has a high inductive impedance at the frequencies of interest. Then you use capacitors to inject the noise into the lines between the inductors and the equipment under test.

The test equipment is a signal generator(s) that can generate the desired frequency and amplitude of the noise. If you state the type, frequency, and amplitude of the noise I can perhaps be more specific.

 

[MikeMl]

Why inject noise into a power line, anyway?

 

[KeepItSimpleStupid]

I know of a way, but it's not injection. It basically means your totally synthesizing the power and creating the disturbances in the synthesis. They are not cheap.

 

[canadaelk]

What kind of noise? Frequencies and levels. Purpose?
Doing it is easy, but before I would give advice, I would like to know the legality of it all! E

 

[4pyros]

Washing Machens, CFLs SMPS without filters.

 

[ChrisP58]

EMC Susceptibility testing

Some years ago I had to do EMC suseptibility testing for a power supply to go onto a military aircraft. The reference standard was MIL-STD-461. I believe the section was CS114.

For conducted noise, the test lab used a special noise injector probe to inductively put noise currents into the power cable. It was basically a current transformer used in reverse. driven by high power RF amplifier.

The standard can be found here: http://www.everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461F_19035/ CS114 starts on page 70.

While this is a military standard, I expect the testing will be similar for commercial and industrial applications.

 

[cachehiker]

Find yourself a microwave oven transformer (we used two with the secondaries in series), power it with a variac, improvise an adjustable spark gap, and build a showering arc noise generator. For lower frequencies typical of conducted EMI, couple the noise into the power line with a 1:1 transformer consisting of a few turns in the primary and the secondary and a higher permeability toroidal core. You can even wind it with two secondaries for injecting common mode noise or wind a dozen or so turns around an air core for higher frequency radiated noise. Radiated noise immunity wasn't much of a problem for us though.

It won't be precise but the noise generated is broadband and it can be used to figure out what sorts of filtering is more effective for a given application. IIRC (it has been a while), an 1/8" gap was putting some pretty nasty 4KV crap on the line at frequencies up to around 10MHz with a 120V input. It would routinely lock up and/or fry just about anything we tested that didn't include some pretty robust filtering. I think we originally set our standard at 45V input with a 1/16" gap for about 1.5KV of noise.

We no longer use it though. Design engineering wanted something more consistent and insisted on our buying an actual pulse generator about 10 years ago. It will pass things set at 2.5KV that the showering arc noise generator routinely crashed at 1.5KV.

 

[4pyros]

showering arc noise generator

Or maybe a chattering relay?