Weber and I are preparing to do a MOSFET and capacitor upgrade to another PIP-4048MS. This one was manufactured in February 2017, and has different MOSFETs and capacitors to the ones we usually see. Wow. Could they have seen the light and upgraded to our recommended specifications, making such upgrades unnecessary from now on?
The MOSFETs are Texas Instruments
CSD19505KCS. This is nearly the same part number as one of our recommended MOSFETs, the
CSD19535KCS. The main difference is the MOSFET rated voltage; they are using 80 V compared to our recommended 100 V. With the lower voltage, they get better on resistance (2.6 mΩ versus 3.1 mΩ), but earlier models used the
IRFB3307, which are 5.0 mΩ). So they've gone from 75 V to 80 V MOSFETs. This is probably adequate if the layout in the battery side of the inverter is exceptionally low inductance, but I don't believe that this is the case.
There are actually two different brands of 48 V bus capacitor installed in this particular inverter. One pair is
Jamicon TK series 3300 μF 80 V capacitors. The 80 V is another improvement, in line with our recommendations. However, the TK series is "general purpose", though with 105°C rating. The rated life is only 2000 hours, compared to 10 000 hours for our recommended part. It also has a low ripple rating, around 2 A [ edit: at 120 Hz; see below ] (it's hard to find real data on this part; it may be a custom manufactured part). The original capacitors were rated at 4.57 A, so they've gone backwards in ripple current rating. It seems to me that in this application, ripple current rating is important, so again, their upgrades don't seem to have gone far enough.
The other pair of capacitors is
Jainghai CD294 series 2200 μF 80 V. Again, the voltage is good, but the life (2000 h) and ripple current rating (2.1 A [ edit: at 120 Hz, see below ]) are poor. The CD294 doesn't seem to be a high ripple current series. The capacitance value (μF) is irrelevant in this application.
So the capacitors have improved in voltage rating, but worsened in ripple current rating. I don't know if this is overall an improvement or not.
[ EDIT:
My bad! I've again been caught by the various manufacturers quoting ripple current rating at different frequencies, e.g. 120 Hz versus 100 kHz. Our recommended capacitor has a 120 Hz ripple current rating of 2.3 A, not much better than the Jianghai at 2.1 A, or the Jamicon at some 2.3 A. Without specifications at 100 kHz, it's hard to tell which is better. The mere fact that our recommended capacitor
has a 100 kHz ripple rating, and that it's a member of a low ESR series, is indicative (but by no means proof of) better high ripple performance. ]
In summary, the improvements are basically welcome, but in our opinion don't go far enough. Still, it will be interesting to see if and how much the reliability improves with the 80 V MOSFETs and capacitors.
[ Edit: qualified "inverter" to "battery side of the inverter" ]
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[ Edit3: Re-inserted UTF8 characters in preparation for testing another forum conversion to phpBB ]
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