Suggestion for an inexpensive non-linear load for 230/115?

[Robbiel Factor]

What can you recommend as a non-linear load? Preferably one that can be bought or constructed inexpensively. Thank you!

 

[Nidum]

This question is too open ended to answer . Please tell us more specifically what you are looking for and why .

 

[Robbiel Factor]

This question is too open ended to answer . Please tell us more specifically what you are looking for and why .

Oh didn't notice the typo. Its for a 230/115 single phase transformer. We would just like to have a non-linear load test on the transformer we made and are looking for possible loads that are non-linear. It is so that we can analyze the harmonics that are occurring when our transformer is connected to a non-linear load.

 

[anorlunda]

Any active device can be a nonlinear load. Nidum is right, your question needs to be more specific. Are you talking microwatts or megawatts? AC or DC? Linearity with respect to voltage? Temperature? Frequency?

 

[anorlunda]

Oh didn't notice the typo. Its for a 230/115 single phase transformer. We would just like to have a non-linear load test on the transformer we made and are looking for possible loads that are non-linear. It is so that we can analyze the harmonics that are occurring when our transformer is connected to a non-linear load.

A diode in series with a resistor is a pretty nasty load.

 

[Jeff Rosenbury]

A low frequency switching power supply will give some harsh "harmonics" (not all of which are integer multiples).

You might try a SCR fed by a resistor with the trigger controlled for random timing (or uniform timing for comparison). Playing with the trigger timing will give lots of control over when the load is drawn. The load itself will approach a square wave with mostly odd harmonics, but I think you should be able to force some even harmonics with clever timing.

 

[Windadct]

Rectifier Bridge and Resistive DC load? - no filtering - would be pretty ugly AC current waveform.

 

[jim hardy]

Anything with rectifiers

It is so that we can analyze the harmonics that are occurring when our transformer is connected to a non-linear load.

You'll of course look at the current waveform with a spectrum analyzer? - you can't distort line voltage very much so you'll have to FFT current... it's loads of fun.. Get a cheap microphone and 'listen' to household appliances, too . Harmonics... on the cheap...
try an ordinary lamp dimmer and big incandescent bulb
a switching power supply like your computer
an induction motor. That one will be interesting to observe when run at rated voltage, 115V when wired for 115, and again run at half voltage 115V applied but wired for 230 . Likewise a decent sized transformer, unloaded
a transformer style battery charger (make sure you get an old fashioned heavy one that hums not a newfangled featherweight SMPS) . It'll draw exaggerated current peaks when charging a battery.

Anorlunda's simple diode-load should be rich in even numbered harmonics. Symmetric rectification should be odd-rich and even-poor.

 

[Windadct]

Can generate over 100% current harmonics with the rectifier and load above - forgot to say (realize) it needs a capacitor in the load:

 

[jim hardy]

That's interesting, windadct

if you let it run does the DC component disappear after a while ?

I'd expect that after say a hundred(?) of those thirty cycle intervals the even harmonics and DC component would almost disappear ?

Is that easy to do with your (impressive) program ?

old jim

 

[Windadct]

Huhh - it is an over simplified - "simulation" - Ideal source and "ideal" circuit / load - but still simpler to say thsn what to expect with a dimmer... yes -- evens would dissipate-esp in the 1 ph case.. - my point being a rectified load creates a crazy non-linear load.

Sorry I do not know if you are being dismissive - it is LT Spice - crazy free and powerful.

 

[jim hardy]

Sorry I do not know if you are being dismissive - it is LT Spice - crazy free and powerful.

no i wasn't being dismissive

i'm not good with computers, on most forums i use the handle "analog"
and i stiill figure my gas mileage with a slide rule.
I have never got introduced to LTspice and i do envy you folks who are fluent with such things old jim

 

[Windadct]

Haha - not fluent - I am trying to become so because I know how good it is. When I went to school spice was a text only simulation and for me, impossible - in this case I wanted to use a simple case to calculate THD which I had not done before ( and it was stupid easy- like almost everything else in EE - the complex can be broken down into simple concepts) -- for a free program it is, IMO, the #1 best tool for EE.

I would recommend everyone give it a try - basic ideal sources, R- L - C circuits, filters - etc...the LT SPice exists so that Linear Technologies can sell product, but there is no ads, or other marketing going on, other than the libraries and examples using LT product.

 

[jim hardy]

so i'll find it with a search on LTspice?

a PF friend gave me a Windows 95 disk so i can make a machine to run Qbasic. I loved to simulate with Qbasic , before that i used TI99's extended basic .

Thanks

old jim