Mosfet versions

Looking at the datasheet for the IRFB4110, I do notice that the on resistance was pretty low for the '4110, which would run lower heat (if properly driven): 3.7milliohms.  Another very important number is the input capacitance: the '4110 clocks in at 9620pF...quite high.

HY3810 has higher on-resistance (5 milliohms), but also a greatly reduced input capacitance (only 7900pF).  This would help the weak LF driver somewhat.

However, the "new" 48v FET is the NCEP039N10.  Kinda hard to find a datasheet for these, but they're rated at 135A.  The plus side is that they have a much lower gate capacitance (6400pF), and are back to the ~3.65milliohms on resistance.  This is basically taking both pluses from the previous two, even though it has a (slightly) lower amperage rating.

Reduced gate capacitance reduces loading on the LF Driver; as far as a GS inverter is concerned, a full bank of '3810s is about the max it can drive cleanly (i.e. not rounding the gate drive waveforms).  The 39N10s are extremely easy to drive because of the greatly reduced gate capacitance.  All I can say about the PJ LF Driver is that it needs a lot of help ;-).

I still think the changes are mostly price-oriented, though it is worth noting that the gate capacitance has gone down with each subsequent FET change.  Maybe there is some rhyme and reason to the changes after all. 

Let's not get started the 24v FETs...those sometimes have a HIGHER on-resistance than the 48v FETs.  Which is completely counterintuitive.  Take the HY3410s used on some 24v inverters: 6.5milliohms on resistance.  Hello??!

1 hour ago, Sid Genetry Solar said:

Looking at the datasheet for the IRFB4110, I do notice that the on resistance was pretty low for the '4110, which would run lower heat (if properly driven): 3.7milliohms.  Another very important number is the input capacitance: the '4110 clocks in at 9620pF...quite high.

HY3810 has higher on-resistance (5 milliohms), but also a greatly reduced input capacitance (only 7900pF).  This would help the weak LF driver somewhat.

However, the "new" 48v FET is the NCEP039N10.  Kinda hard to find a datasheet for these, but they're rated at 135A.  The plus side is that they have a much lower gate capacitance (6400pF), and are back to the ~3.65milliohms on resistance.  This is basically taking both pluses from the previous two, even though it has a (slightly) lower amperage rating.

Reduced gate capacitance reduces loading on the LF Driver; as far as a GS inverter is concerned, a full bank of '3810s is about the max it can drive cleanly (i.e. not rounding the gate drive waveforms).  The 39N10s are extremely easy to drive because of the greatly reduced gate capacitance.  All I can say about the PJ LF Driver is that it needs a lot of help ;-).

I still think the changes are mostly price-oriented, though it is worth noting that the gate capacitance has gone down with each subsequent FET change.  Maybe there is some rhyme and reason to the changes after all. 

 

Let's not get started the 24v FETs...those sometimes have a HIGHER on-resistance than the 48v FETs.  Which is completely counterintuitive.  Take the HY3410s used on some 24v inverters: 6.5milliohms on resistance.  Hello??!

Yet the NCE60H15s are down at 4.5milliOhms and also 6500pF. Guess it all depends on what you get.

1 minute ago, Waterman said:

Yet the NCE60H15s are down at 4.5milliOhms and also 6500pF. Guess it all depends on what you get.

Still, that's a higher on resistance than the comparable "48v" FET at 3.5milliohms.  Seems kinda dumb to me: just use the "48v" FET...

You beat me to it!  I was going to ask why not just use the 48v fets for all the inverters?  Besides the advantages you mentioned, they could save themselves some stocking and supply headaches, and they would probably get a better price by buying more of one value.

That's what we're already doing with the GS inverters...for the ones with the universal transformer, anyway.  Just need to find a fan that can run from 8-75v and changing system voltage would only require changing the transformer setup... 😉

On 2/22/2021 at 9:56 PM, Sid Genetry Solar said:

That's what we're already doing with the GS inverters...for the ones with the universal transformer, anyway.  Just need to find a fan that can run from 8-75v and changing system voltage would only require changing the transformer setup... 😉

Well that should be an easy thing to do, just add a buck converter to those with higher than 24 Volts. 😉  That should take you all of 10 minutes to design in.

It appears that they are also cheaper. $0.05 each in lots of 15,000 or more.

So here's the problem: if we get our 250CFM custom fans in 12v, they will use FOUR AMPS each.  Times a maximum of 4 fans/inverter, that's a minimum of 16 amps continuous output required.  This pretty much requires a synchronous buck converter (i.e. more complicated)...and even so, the buck converter will have to be fairly sizable to handle this current--and will have to be mounted in front of a fan so it doesn't burn itself up. 

Oh, and it needs an input voltage range of 16-80v.  Not exactly a weekend project.

There are a few off-the-shelf potted buck converters that show a good bit of promise (15A max, up to 90vIN), but the input voltage range is quite limited.  I have several of 'em, they're wonderful little units mounted in a heatsink shell...but if the input voltage falls below the limit, they cut completely out, no voltage output.  Bit of an issue...not to mention they cost well past $20/ea.

Can the fans run off the AC output of the inverter? Or even add an auxiliary winding to the transformer just for the fans?

We have definitely considered that as a possibility...it's quite attractive due to the fact that the DC input voltage doesn't affect the fans.  However, there are a few issues:

• Fans can only run if the inverter is running.  If the fans are powered by the AC output, they cannot run if the inverter shuts down due to an overheat error.  I agree this is pretty minor, though Sean will disagree with me...
• The GS inverter setup allows all fans to be smoothly PWM controlled from 0-100% throttle as needed based on the measured temperatures.
  • While it's not impossible to PWM-control a 120vAC fan with a chopper circuit, etc., it is a good bit more complicated, also requiring an isolated control circuit.  Assuming the fan is very efficient (most AC fans don't seem to, though!), it probably could be controlled via an opto-TRIAC, though then the WiFi board has to sync to the AC output frequency as well.  Yeah, I've done chopper circuits before...not impossible.

I've seen mention of rebranded Chinese inverters that have one fan running at full speed all the time...conversely, all GS inverters "test" the fans at startup, then (providing temps are low enough) all fans will come to a complete stop.  My house inverter (GS-based, though it's housed in a PJ chassis...designers get the cast-offs and "mutt" systems 🤣) is pretty much completely silent most of the time.  Ran the mini-split in heat mode yesterday for about 5 hours, pulling a continuous 800W...and after about an hour, the fans started running at a very low throttle.  Could barely tell unless you were standing right in front of the closet.

Now when I had the PJ AS5 transformer in there, any significant load would get those fans ramping up to full speed (= 136F) very quickly.  Want to cook something on the stove?  Prepare for the sound of a jet engine in the closet...in less than 5 minutes 🤪.

12 minutes ago, Sid Genetry Solar said:

We have definitely considered that as a possibility...it's quite attractive due to the fact that the DC input voltage doesn't affect the fans.  However, there are a few issues:

• Fans can only run if the inverter is running.  If the fans are powered by the AC output, they cannot run if the inverter shuts down due to an overheat error.  I agree this is pretty minor, though Sean will disagree with me...
• The GS inverter setup allows all fans to be smoothly PWM controlled from 0-100% throttle as needed based on the measured temperatures.
  • While it's not impossible to PWM-control a 120vAC fan with a chopper circuit, etc., it is a good bit more complicated, also requiring an isolated control circuit.  Assuming the fan is very efficient (most AC fans don't seem to, though!), it probably could be controlled via an opto-TRIAC, though then the WiFi board has to sync to the AC output frequency as well.  Yeah, I've done chopper circuits before...not impossible.

I've seen mention of rebranded Chinese inverters that have one fan running at full speed all the time...conversely, all GS inverters "test" the fans at startup, then (providing temps are low enough) all fans will come to a complete stop.  My house inverter (GS-based, though it's housed in a PJ chassis...designers get the cast-offs and "mutt" systems 🤣) is pretty much completely silent most of the time.  Ran the mini-split in heat mode yesterday for about 5 hours, pulling a continuous 800W...and after about an hour, the fans started running at a very low throttle.  Could barely tell unless you were standing right in fronoset.

Now when I had the PJ AS5 transformer in there, any significant load would get those fans ramping up to full speed (= 136F) very quickly.  Want to cook something on the stove?  Prepare for the sound of a jet engine in the closet...in less than 5 minutes 🤪

I can tell you about a circuit I rigged to control motor speed from an existing  AC speed controller. It isn't very sophisticated, but I thought it was clever. And the control circuit stays isolated. Since you are already PWMing for control, it would probably work directly.

I had a speed controller with a knob. The knob obviously turns a pot. Well... I replaced the pot with an LDR. I stuck it into a tube with an LED facing it. By PWMing the LED, I could control motor. It worked very well. Of course, not very elegant, but super practical.

As far as temperature, could you maybe set a point where instead of dropping the transformer out, you first drop the external load, leaving the transformer running the fans? Set another point which shuts it all off if the temperature continues to rise maybe? 

Of course, there are fans available in 12, 24, and 48 volts too...

2 minutes ago, InPhase said:

As far as temperature, could you maybe set a point where instead of dropping the transformer out, you first drop the external load, leaving the transformer running the fans?

Not with the current setup.  There is no relay shutoff for the output (extra $$$).

2 minutes ago, InPhase said:

I had a speed controller with a knob. The knob obviously turns a pot. Well... I replaced the pot with an LDR. I stuck it into a tube with an LED facing it. By PWMing the LED, I could control motor. It worked very well. Of course, not very elegant, but super practical.

All of the AC wave chopper circuitry had to have been handled in the speed controller--yeah, super easy that way...but a smidge more costly.

9 minutes ago, InPhase said:

I can tell you about a circuit I rigged to control motor speed from an existing  AC speed controller. It isn't very sophisticated, but I thought it was clever. And the control circuit stays isolated. Since you are already PWMing for control, it would probably work directly.

I would assume you are familiar with the function of a TRIAC?  (If not, SCRs?)  Basically, for an AC-wave chopper to function, you have to base all timing off of the AC zero crossing when the TRIAC turns off.  Which is why the WiFi board would need an AC sync input in order to functionally drive an opto-TRIAC in AC-chopper mode.

3 minutes ago, InPhase said:

Of course, there are fans available in 12, 24, and 48 volts too...

Yeah, we have to get the GS fans custom-made to our specifications for a wider voltage range.  Most of the off-the-shelf 12, 24, 48v fans have an extremely small voltage range--for example, many Delta 48v fans have an absolute maximum voltage of 53v.  An off-grid 48v system can easily reach 60v+ with a temperature-compensated absorption charge on lead-acid batteries...bit of a problem. 

I personally have a 16S LiFePo4 bank (peak charge voltage: 56.5v), with some stock 48v Deltas (FFB1248EHE) in my house inverter...and I've had one of them fail on me after several months of use.  Smelled pretty bad, too...so far the other 2 are still working fine, fingers crossed...

Putting a fan with a certain voltage into an inverter is not an issue--unless the customer wants to void their warranty and change the system voltage down the road--everything in the inverter can handle a different voltage (12/24/36/48 for the 3k and 6k GS) after proper reconfiguration...but the fans may need replaced.  We'll see, I may find (or be able to make) a super-efficient buck (or boost) converter that makes it real easy to use just a single fan voltage across the board in our inverters.

Sounds like you have thought it through. It's nice to see that from a company.

I usually do, but unfortunately that tends to mean that if I'm stumped, finding a solution can be very difficult!  Oh well.