Basic inverter questions / electronics

Dear all,

I'm going solar powered and plan to do some DIY stuff as well here, for generating 230V/AC power (Europe).

After having this read, I'd have some (maybe) interesting questions.
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1. Are DC to 230V/50Hz (or 110/60) inverters actually amplifiers, modulated with the corresponding 50 or 60Hz signal ?
- They have a constant DC source
- They have an input signal (50/60Hz sinusoidal)
- They have a fixed output voltage (this is what we perceive normally as 'volume', right?), even while loaded
- not sure what kind of impedances they have but ..


2. Thinking further point 1: can a 230V output voltage generating Class D amplifier, fed with 50/60Hz sinusoidal signal on the input be treated like a constant voltage source for some lightweight AC outlet based commercial device ? Just in theory. Let's take a Hypex Class D module, feed it with 50/60Hz sinusoidal signal, no volume control (=max power) and then transform the output's resulting AC waveform with a trafo to the desired voltage.

3. How does an inverter usually handle the slow drop in DC while battery is depleting, keeping a constant output sinusoidal voltage ? (I assume available power drops in such a case but if we would like to suck all of the energy out of the DC source we could make something like this, right? Always keeping same voltage AC on the outputs).
- calibrating the inverter to a fixed input DC voltage and cutting everything above it at the input side with a linear stabilisator would be waste of energy in form of heat and make the solution inefficient
- is there something like multiple primary or multiple secondary transformer, which is used in each 1 Volt drop as DC source is depleting slowly ? (switched by relays). Keeping 50/60Hz modulated AC signal close to nominal 110/230V and the rest minor deviation would be corrected otherwise ?




Or maybe some kind of switching solution ? So that the inverter can use 14V -> 3-4V DC on the input side while constantly producing stable sinusoidal 230V/50Hz (in my case) on the output, regardless of input DC voltage within range ? Load would be small, within range of input DC or if I need more energy on the output side I specify tighter allowance on DC side (like 14V -> 8V, not lower).

PS: hobby project, don't take it too serious. Just want to figure out basic electonics, I'm on a learning path. Thanks for you patience. :)
 
Last edited:

Vovk Z

Member
2011-10-30 10:32 pm
Kyiv
2. Thinking further point 1: can a 230V output voltage generating Class D amplifier, fed with 50/60Hz sinusoidal signal on the input be treated like a constant voltage source for some lightweight AC outlet based commercial device ? Just in theory. Let's take a Hypex Class D module, feed it with 50/60Hz sinusoidal signal, no volume control (=max power) and then transform the output's resulting AC waveform with a trafo to the desired voltage.
In general your idea could work, but ClassD amplifiers usually don't have enough supply voltage range.
DC voltage after solar panels varies too much, from zero to some peak value.
 
- the term "amplifier" doesn't fit what they do, because they are dc-ac converters. Internal structure may be different.

Many DC-AC inverters do not actually generate sinewave voltages. They often look like a stepped staircase wave with say 8 or 16 different levels. They are more like an SMPS with changing levels.

Jan
 
Regarding point 3, you could use a step-up (boost), step-down (buck) or buck-boost converter to convert the DC voltage to whatever you need and then apply a bridge, or indeed use a transformer. I don't know what method is normally used, though. I expect that having galvanic insulation from the grid is needed for safety reasons.

By the way, the term maximum power point tracker might be of interest; solar cell inverters use various different types of algorithms to load the solar panels such that they deliver maximum power.