High Voltage High Current Waveform Generator

[ksnyder]

I do a lot of work on off-grid solar systems.  These systems use a battery bank to store the DC coming from the solar panels and the house is powered through an inverter.  These inverters are often called "pure-sine-wave" - but they are not.  Off-the-shelf electronics products tend to work more-or-less with these power sources, but there is a lot of flicker and rectifiers don't work the way you expect them to. 

When attempting to troubleshoot and fix problems, I have two distinct problems.  It would be nice if there was something that could solve both.

1. When I am testing things at site, the only power available is a choppy, unpredictable 120V almost-sine wave.  I would like to be able to provide a very clean source of AC for testing.  A transformer won't do it because it will just copy the bad waveform.  An inverter could do it, but it would need a DC source to feed it.

2. When I am back in the lab, I have clean AC power, but no way to test my circuits on an iffy sine wave.

In my imagination, this has to be a common problem that people face.  Perhaps I just don't know where to look.  If this isn't a common problem, then I thought that it might be practical to use a signal generator with a waveform amplifier to achieve 120VAC.  But, I am going to need something like 10 amps to be able to test everything I would like to work on, which seems beyond the capabilities of most waveform amplifiers.

Any help or guidance would be appreciated.

Kelly

[alm]

If you want an actual waveform generator, i.e. something that can generate a variety of signals, then something like the Kepco BOP might come to mind. Only goes up to +/- 100 V, however, and do not ask about the price.

If your bandwidth requirements are modest, you could run one of them through a transformer to get to 120 V_RMS. Keep in mind that they are much more sensitive than DC power supplies, and may not be happy with capacitive and inductive loads.

[Berni]

You probably want a really really big audio amplifier. To provide you with the voltage and current you want it will likely have to be over 3kW. Hopefully you don't need the setup to be very mobile because it will be pretty big and heavy. But this will give you a pretty much perfect sine wave as long as you feed one in to the amplifier.

Another off the shelf thing that does this are VFD motor drives. They turn AC in to high voltage DC and then chop that up back in to AC at a variable frequency and voltage. Tho they are built for 3 phase output and probably also make a crappy looking sine wave.

[David Hess]

These inverters are often called "pure-sine-wave" - but they are not.  Off-the-shelf electronics products tend to work more-or-less with these power sources, but there is a lot of flicker and rectifiers don't work the way you expect them to.

If they are not producing sine waves then they should not be called "pure sine wave" inverters.  This goes double since inverters which produce actual sine waves are commonly available.

Rectifiers should not care whether supplied from a modified sine or pure sine source.

1. When I am testing things at site, the only power available is a choppy, unpredictable 120V almost-sine wave.  I would like to be able to provide a very clean source of AC for testing.  A transformer won't do it because it will just copy the bad waveform.  An inverter could do it, but it would need a DC source to feed it.

A ferroresonant or constant voltage transformer will clean up a dirty source.  Most if not all online UPS units produce a sine wave output; they could be treated as a sine wave inverter with included battery.

2. When I am back in the lab, I have clean AC power, but no way to test my circuits on an iffy sine wave.

A standby UPS with a modified sine wave output would be a cheap source and is what I have used in the past for this.

[Deni]

Just saw this thread - if you did not find the solution, take a look at HP6811 series of programmable AC power generators or Model 9801 from BK Presision. There are also other manufacturers...

[Neomys Sapiens]

For Lab testing stuff with AC supplies with any conceivable disturbance added, look for the products of Spitzenberger&Spies. There are others too of course. But their stuff is really good.

[schmitt trigger]

You may want something like this:
https://www.chromausa.com/product/low-power-programmable-ac-source-61600/