RCD type with an iBoost+

[JohnW2]

These immersion boost affairs are the equivalent of a PWM lighting dimmer connected to the immersion heater. ... 230V AC input, output is a chopped sinewave.
Input current will follow the chopped AC output.

Indeed - as I've now discovered. I had previously thought that they might be a bit more clever than that, enabling solar power to be used for supplying an immersion in the absence of the grid supply - but seemingly not

Just like lighting dimmers, minimum of a Type A RCD required assuming you are having an RCD at all.

Indded, and it's that last bit is what Irecently questioned (by implication). Although eric seems to feel the need for it, I'm not sure I would feel it necessary to have RCD protection of a circuit supplying only an immersion.

 

[JohnW2]

They claim it is modulated dc - do you have other information?

It's described as DC with PWM - but I now strongly suspect that,as flameport has suggested, it's probably just chopping the AC waveform- i.e. such that the magnitude of pulses varies during the (AC)_ cycle, as well as their width being 'modulated' to achieve control.

Kind Regards, John

 

[DetlefSchmitz]

but I now strongly suspect that,as flameport has suggested, it's probably just chopping the AC waveform

So you are just guessing too. The only person who can tell us for sure is Eric who can look at the output on a scope, but I suppose that won't happen either.

 

[plugwash]

I did some searching and managed to find a teardown/reverse enginnering video.

 

[JohnW2]

So you are just guessing too. The only person who can tell us for sure is Eric who can look at the output on a scope, but I suppose that won't happen either.

Yep, in the absence of more information, we can do nothing but 'guess' - but it can at least be an attempt at 'intelligent guessing'. I can't see why they would bother to rectify and smooth the AC and then chop it into pulses of roughly equal amplitude (which is about the only other sort of 'PWM' it could be), when it is simpler just to chop a full-wave-rectified waveform.

In any event, despite the guessing as to whether the pulses are of roughly equal amplitude or varying through each half-cycle, I don't think that makes a blind bit of difference to what we have been discussing, does it?

Kind Regards, John

 

[DetlefSchmitz]

So the guess was incorrect, and the manufacturer was not lying after all.

 

[plugwash]

It looks like what we finally ended up with was somewhere between my guess and flameport's guess. The input *IS* rectified, but the DC is never smoothed and then the rectified output is PWM'd. It's unfortunate that the video author was unable to test it properly as he didn't have the sender, so we only got to see the waveform in "max power" and "off" modes.

 

[ericmark]

Very interesting video and it seems it is DC, after the unit.

 

[JohnW2]

So the guess was incorrect, and the manufacturer was not lying after all.

Whose guess? Wasn't I right when I wrote ...

.... I can't see why they would bother to rectify and smooth the AC and then chop it into pulses of roughly equal amplitude (which is about the only other sort of 'PWM' it could be), when it is simpler just to chop a full-wave-rectified waveform.

Kind Regards, John

 

[JohnW2]

It looks like what we finally ended up with was somewhere between my guess and flameport's guess. The input *IS* rectified, but the DC is never smoothed and then the rectified output is PWM'd.

Indeed -and,as I've just written,that sounds like what I recently suggested

Kind Regards, John