Building an AC Load 

with a dc load

electronic load Model EE30120a

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Here is how you build an AC Load
out of a
DC Electronic Load.

( Requires Adobe Acrobat Reader ) Version 5.0 / PDF  Format
How to build an AC Electronic Load    ANEE-143    File Size: 250K or Less 
  • #1 You need a DC Electronic Load that is equal to the power you want to pull, and that will work at low voltages.

    • Note: The loads need to be able to the follow the full wave bridge frequency ripple current.  

  • #2 You need an Isolation step down transformer that is about a 4 to 1 ratio.  (120 Vac input to about 26 Vac output) 

    • Please Note: You will need an isolation transformer that is about 20% to 50% bigger than the load you want to pull, this has to do with the B/H curve and flat topping of the sine wave of the isolation transformer. If you are doing frequency sweeps you may need to go 100% bigger in power size of the isolation transformer. 
      You can also use a isolation transformer that is 3 phase for special cases. The Isolation transformer stops current loops between the electronic load and the Inverter circuits.  The Isolation transformer also helps impedance match the input power to the load power. 

  • #3 You need Rectifier Diodes that will handle the current in most case 2 to 4 times the current being pulled through the 26 Vac side.

    • Note: You can not create or destroy power so if the voltage is transformed down then the current goes up!   { Right..! }  Make sure your Rectifer Diodes are big enough...!

  • #4 You need filter capacitors for the full wave bridge circuit and a capacitor for each load that is in parallel.

  • #5 You need to fuse the 120 Vac input side of the isolation transformer for the power the Loads are rated for, you don't want to blown them up.  

  • #6 You just saved yourself $10,000 or more...!!!

Ok?   So what are the drawbacks doing it this way....???

  • #1 You can't change the Phase of the Current / Voltage

  • #2 You can't get down to 0 Vac the lowest voltage is going to be about 5 Vac if you are inputting 120 Vac

  • #3 If you are doing a frequency sweep for efficiency it may not be accurate. 


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