Warpverter

A Serious Electronic Project For The Expert DIYer

What is a Warpverter?

A Warpverter is a DC In - AC Out Inverter used for off-grid applications.

It can be designed to operate with a wide range of battery voltages … supply an output of 120V or 240V AC (which can include split phase) … 50/60Hz ... and at levels from a few kW through to tens of kW.

It is a DIY or Build-Your-Own concept and is not available commercially.

While it was initially called a Step Inverter … it eventually became known as a Warpverter.

The Warpverter was designed by Tony Le Grip, a retired professional power electronics design engineer from Melbourne, Australia ... who posts on various forums as "Warpspeed" and hence the name.

Tony originally posted details on thebackshed.com forum and later on diysolarforum.com which he still frequents … and is happy to discuss all aspects of the design … and help anyone building or considering to build one.

As mentioned, the inverter is suitable for off grid use and can be designed for a wide range of battery voltages … from 24V through to 100's of volts ... and for whatever output level desired.

Examples have been built to run from 24V, 48V, 100V and even a 3-phase version running on a 200V Toyota Prius battery … and in sizes from approximately 3kW through to 15kW … though much higher levels are possible.

To our knowledge, no split phase versions have yet been built … though is certainly possible through the appropriate winding of the transformer secondaries ... see more detail here

Tony’s original 5kW unit is still running his home after 7 years of continuous use ... and Roger's 15kW build has generated over 9,000kWh in the nine months since installation.

This site has been put together to collate all the information needed for anyone interested in building a Warpverter ... with links to further information and online calculators.

These resources are totally free and completely open source.

Tony's 5kW Warpverter Output and Heatsink

Warpspeed's 5kW Warpverter closeup of IGBTs

➤ Who designed the Warpverter?

Tony Le Grip, a retired professional power electronics design engineer from Melbourne, Australia

Tony is also known as "Warpspeed" on the forums he frequents

➤ What can you power with a Warpverter?

A Warpverter is a normal inverter and so can power anything a normal inverter can power ... as long as it is within the power capability of the inverter.

One huge advantage is that Warpverters have a massive surge capability so can start motors and loads with heavy startup current easily.

➤ What DC input voltage limits are there?

There's no major restrictions, it's a matter of designing the Warpverter for the batteries you plan to use. Anything from 24V to as high as you feel comfortable with.

Bear in mind, the higher the voltage the lighter gauge cables and windings you may be able to use.

Tony's Warpverter uses 100V Lithium cells and others have used 48V in either FLA or Lithium. A 3-phase version has also been built to operate on a 200V Toyota Prius battery.

➤ What batteries are best suited?

There's no real issue using whatever battery chemistry you desire ... as long as it has the capability of running the sorts of loads you plan to use ... and you have sufficient charging capability

➤ Can they be built for split phase operation?

The basic Warpverter builds up a stepped single phase 240v sine wave voltage, by combining in series, the secondaries of four independent transformers driven by the appropriate digital waveforms.

Its really a form of direct digital to analog conversion at very high power.

Two separate isolated 120v outputs can be generated from the same four transformers by arranging each transformer to have a pair of separate secondary windings, each of half the nominal voltage of the basic Warpverter.

That then will produce two 120v isolated outputs which could either be used in parallel for full inverter output power at 120v, or if connected in series, 240v split phase.

➤ Can a Warpverter be used as a grid tie inverter?

➤ Can you AC-Couple a Grid Tie Inverter to a Warpverter?

Yes ... there are examples out in the field.

➤ What sort of idle power does a Warpverter consume?

Tony's 5kW Warpverter has an idle power of 32 Watts and Roger's 15kW is 35 Watts.

I believe the best to date is one that is 20Watts for a 7kW inverter

There is a bit of luck involved that concerns the quality of the core material used in the transformers. Some material is excellent, and some less so....

➤ Could a Warpverter provide 3 phase power?

Yes, a three phase Warpverter can be built ... and obviously will require three sets of four transformers.

As mentioned above, a three phase Warpverter has already been built.

➤ Could you rewind a three phase transformer to replace the individual transformers in a Warpverter?

No.

➤ If the design is so robust and uses easily available parts, why are they not in production?

It's really boils down to a matter of cost for all the copper wire and transformers. HF inverters are so much cheaper due to not needing large, heavy and expensive transformers.

It is probably really only viable for the DIY market where builders can source suitable second hand material and wind their own transformers.

➤ What are the main advantages of the Warpverter design?

The biggest advantage is all the switching is done at a very low frequency, so the circuit layout is far less critical than high frequency pwm, where it becomes increasingly difficult to successfully parallel multiple devices for very high power.

There are no data screens or firmware. It's a basic bare bones inverter, dc in, ac out.

The simplicity of the system means that it is much more easily repaired and less skill is required if any faults occur.

It's also fully bi directional. Really nasty highly reactive loads can bounce out of phase current right back onto the dc bus.

It also has massive surge capability, fully protected on the ac side with just a normal C curve thermal/magnetic circuit breaker.

If someone needed a 10Kw, 20Kw, or 30Kw inverter, this would scale up really easily, especially compared to a pwm type inverter where anything over about 5kW becomes problematic. Though bear in mind the transformers would obviously need to be suitably large.

➤ What are the main disadvantages of a Warpverter?

Winding four transformers is a huge undertaking, and not to be taken lightly. But if serious power is your goal, a Warpverter is likely to cause you much less long term grief. Its a lot of work, but you only have to do it once !

Of course the expense involved for copper wire and toroid or transformer cores is much higher than for a pwm transformer inverter build.

And then the finished weight is also much more than a pwm inverter.

Below about 4kW-5kW a conventional pwm transformer inverter would be cheaper to build.

➤ What surge capability does a Warpverter have?

Warpverters have a massive surge capability

➤ Is there any software to set up or be updated regularly?

No, not if using Tony's control board. That has no software at all.

A couple of others have been built using an Arduino for control, so they could potentially be updated or modified depending on who built them.

➤ How does the feed forward voltage control work?

Most inverters use voltage feedback to maintain a constant output voltage with changes of dc input voltage and load.

The main problem with that is its slow to correct.

The correction must be introduced slowly, or it can over correct and become unstable. Sudden large step changes in load (up or down) can cause annoying sags and surges in voltage resulting in light flicker.

The inverter output voltage will eventually settle, and then remain fairly constant.

Feed forward works in an entirely different manner.

The dc input voltage is measured, and the inverter can then very quickly adjust the waveforms driving the output transformers to compensate for any change in dc input voltage. The result is that the reaction time of the inverter to sudden dramatic load change can be made much faster acting.

It can compensate pretty much perfectly for input voltage variation over a very wide 2:1 dc input voltage range.

The down side is that although the transformer primary waveforms are well corrected, the transformer secondary voltages do fall slightly with increasing inverter load.

Voltage droop in my own 5Kw Warpverter is about ten volts (at 240v) from zero load to the full 5Kw rated output. That should be pretty typical, all mainly due to unavoidable voltage drop under load in the transformers.

The grid supply here varies more than ten volts anyway from day to day, and hour by hour, and none of my household appliances seem to mind. So I don't think its necessary to have a precise inverter set output voltage.

What is much more important is to have very fast voltage corrections for sudden step load change, and feed forward correction provides that.

Its especially good at reducing light flicker during the starting of large motors.

Its much easier and faster and more accurate to measure a dc voltage than an ac voltage, which is a constantly changing sine wave at 50/60Hz anyway.

The incoming dc is measured in a dual slope integrating a/d converter (to average out impulse noise) on the dc, and the measured voltage used to address one of 256 different lookup tables in ROM.

These lookup tables cover a 2:1 input voltage range, and allow for a very fine adjustment of inverter output voltage. Large very sudden jumps in voltage correction are possible, and always occur right at a zero crossing, so there are never any waveform discontinuities created from large applied corrections.

This can all be achieved with some simple robust and reliable hardware. The lookup

tables contain direct simple gate drive data to the four power switching bridges, there is no software or data manipulation involved.

➤ Where can you buy transformers to suit a Warpverter?

That is the $64,000 question. Unless you are very lucky and can find the odd transformer that can be used ... you either have to wind them yourself ... or have them wound professionally.

Considering the potential of a well built Warpverter, that is still quite viable ... but it seems to be the biggest deterrent for most home builders.

Click Circuits to Open High Resolution Versions

Warpverter Control Board

Warpverter Half Bridge Board ... 8 required

Tony's Warpverter showing the four transformers

Contact:Visit this thread on diysolarforum and message Warpspeed or rogerdw