Pv solar install the inverter in loft or garage

don0301

Dave_Fowler wrote: »

Google has nothing to do with it. Don't insult me.

I have been working in defense and industrial electronics as a design engineer, project manager and latterly (for the last 26 years) as a self-employed electronics circuit designer. Reliability of components and circuits has been of major concern to me since the mid 1960's.

I'm not sure if you think the temperature will not cycle if the temperature is above 150C or if you think the failure of wire bonds or substrates will not occur above 150C. My statement was to say that failures in semiconductors at junction temperatures below 150C are mainly due to temperature cycling.

Dave F

which means an ambient temperature closer to the inverter internal temperature would make it more reliable?

Dave_Fowler

don0301 wrote: »

still waiting for your cable length measurements, so we can all calculate your losses

I'm not certain what the length of my cables has to do with this argument.

The losses in a cable are proportional to the square of the current through it. It does not matter if the cable carries AC or DC. If you need to run 20 meters of cable between your loft and the connection to the mains grid the losses will be lower if the cable carries a lower current. If the DC cables carry a lower current than the AC cables it obvious to anyone with any electrical knowledge that the DC cables can be of a smaller diameter for the same electrical power loss.

I'm sure GrahamC will agree that the national grid carries high voltage / low current to minimize losses. If your DC voltages are higher than 240V then it is advantageous to have the longer runs at DC.

I of course am neglecting losses due to the RF radiation from wires carrying AC before someone jumps on that band wagon.

Dave F

don0301

Dave_Fowler wrote: »

I'm not certain what the length of my cables has to do with this argument.

The losses in a cable are proportional to the square of the current through it. It does not matter if the cable carries AC or DC. If you need to run 20 meters of cable between your loft and the connection to the mains grid the losses will be lower if the cable carries a lower current. If the DC cables carry a lower current than the AC cables it obvious to anyone with any electrical knowledge that the DC cables can be of a smaller diameter for the same electrical power loss.

I'm sure GrahamC will agree that the national grid carries high voltage / low current to minimize losses. If your DC voltages are higher than 240V then it is advantageous to have the longer runs at DC.

I of course am neglecting losses due to the RF radiation from wires carrying AC before someone jumps on that band wagon.

Dave F

if you look, that post was directed at zeupater

Dave_Fowler

don0301 wrote: »

better tell the National Grid that

They already know and take advantage of the fact.

It is rare I despair of the information in the posts but just where are you coming from? I don't understand your logic.

Dave F

don0301

Dave_Fowler wrote: »

I'm not certain what the length of my cables has to do with this argument.

The losses in a cable are proportional to the square of the current through it. It does not matter if the cable carries AC or DC. If you need to run 20 meters of cable between your loft and the connection to the mains grid the losses will be lower if the cable carries a lower current. If the DC cables carry a lower current than the AC cables it obvious to anyone with any electrical knowledge that the DC cables can be of a smaller diameter for the same electrical power loss.

I'm sure GrahamC will agree that the national grid carries high voltage / low current to minimize losses. If your DC voltages are higher than 240V then it is advantageous to have the longer runs at DC.

I of course am neglecting losses due to the RF radiation from wires carrying AC before someone jumps on that band wagon.

Dave F

I have no idea what your even arguing about

as far as i know present solar panels generate dc power

there is a "loss" in the cables, the longer the cable the bigger the loss

i was asking zeupater for his measurements so we could all calculate the losses.

sadly he seems to have gone shy to show them.

Dave_Fowler

don0301 wrote: »

Grats

so your saying an inverter internal temperature is sometimes/often/always above 150C?

Find any single word, line, sentence or anything in my post which says that the temperature is like that. I quoted that the heatsink temperature of an inverter running at full power is likely to be 95C. I calculated that for the junction temperature to remain lower than 150C the semiconductor power had to be limited to 110W - less than half its power rating at tc=25C. I then said that some inverters would have to run at reduced power to cope with the high ambient temperature.

Dave F

Dave F

Dave_Fowler

don0301 wrote: »

which means an ambient temperature closer to the inverter internal temperature would make it more reliable?

What the statement means is that for semiconductors at temperatures below 150C it is best to run them at a constant temperature - be it 0C or 100C - but above 150C other failure mechanisms become prevalent.

If the ambient temperature varies a lot or if the temperature control (fan) in the inverter does not keep the internals at roughly a constant temperature, the failure rate will increase.

Dave F

don0301

Dave_Fowler wrote: »

Find any single word, line, sentence or anything in my post which says that the temperature is like that. I quoted that the heatsink temperature of an inverter running at full power is likely to be 95C. I calculated that for the junction temperature to remain lower than 150C the semiconductor power had to be limited to 110W - less than half its power rating at tc=25C. I then said that some inverters would have to run at reduced power to cope with the high ambient temperature.

Dave F

Dave F

that was my point

don0301

Dave_Fowler wrote: »

What the statement means is that for semiconductors at temperatures below 150C it is best to run them at a constant temperature - be it 0C or 100C - but above 150C other failure mechanisms become prevalent.

If the ambient temperature varies a lot or if the temperature control (fan) in the inverter does not keep the internals at roughly a constant temperature, the failure rate will increase.

Dave F

actually, what you stated was:

At temperatures up to 150C, failures due to temperature in semiconductors are mainly due temperature cycling where fractures in bonding wires and substrates can occur

which brings me back to my previous point:

Dave_Fowler wrote: »

What the statement means is that for semiconductors at temperatures below 150C it is best to run them at a constant temperature - be it 0C or 100C - but above 150C other failure mechanisms become prevalent.

If the ambient temperature varies a lot or if the temperature control (fan) in the inverter does not keep the internals at roughly a constant temperature, the failure rate will increase.

Dave F

so, that'll be an ambient temperature closer to the inverter internal temperature?

Dave_Fowler

don0301 wrote: »

that was my point

Sorry Don, I have missed your point, and looking back to your previous post I now don't understand what point you were raising - if it wasn't the one I answered.

Dave F