Solar Converter 16A Linear current boosters frying.

atilevatilev Posts: 11Registered Users ✭✭
Hello everyone,
We've been working on a project where we have a Dankoff solarforce piston pump  (http://dankoffsolarpumps.com/pdfs/Dankoff_SolarForce.pdf)
pushing water up hill for a village in Rwanda. We have 2 x 250W panels that are in parallel powering the whole thing.

The pump controller is here: http://www.solarconverters.com/products/motor-andor-pump-controllers/solar-direct-pump-driver-lcb-linear-current-boostermotor-driver/ppt-1224-15/

So far we've burned 2 of these pump controllers. The FET's on the second one fried today after working for a month. This is really odd, as these LCB's should be lasting years. We had checked with the manufacturer on the settings and they had given their blessing on the panel configuration. AFAIK the voltage and current coming form the panels are within

Enclosure box was mounted in the shade and never in direct sunshine.

Any idea's? Anyone had similar failures from this device?

Thanks,
Alp

Comments

  • BB.BB. Posts: 27,887Super Moderators, Administrators admin
    In general, FETs need to be well heat sinked. Does the "LCB" have good ventilation around it? Can you mount the LCB to a large piece of metal (aluminum, steel plate, etc.--perhaps painted/treated to prevent corrosion/rusting) to better dissipate heat?

    There has been big issues with FETs and other transistors being counterfeited. At times, even reputable suppliers have been hoodwinked.

    https://hackaday.com/2017/07/15/lets-play-spot-the-fake-mosfet/

    And it is possible that the LCB is simply under designed... You are not doing anything "different" like switching power on and off under load? (inductance of the wiring and motor can cause ringing and high voltage spikes when power is switched under load).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Posts: 2,205Solar Expert ✭✭✭✭✭
    Heat may be the enemy, being in an enclosure, perhaps a fan with the same voltage as the pump creating active cross  ventilation would help, certainly won't hurt, a 2 pin fan like these for example https://www.ebay.com/b/24V-120mm-2-Pin-Computer-Case-Fans/131487/bn_2788697
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • atilevatilev Posts: 11Registered Users ✭✭
    Hi Guys,
    Thanks for the responses, The FET's are mounted on a large piece of aluminum on the back of the PCB. So if it is a thermal problem Adding a fan would be the only choice I presume.  It's in an IP 65 metal box so heat dissipation should work. I'd rather not have any moving parts and have only heatsinks for getting the heat away. (moving parts break)


    Regarding not having original ones. I'd have to take a close look.


  • NANOcontrolNANOcontrol Posts: 78Registered Users ✭✭
    An old post, but look at the board.  The FET pin out is set up for TO-220 and TO-247.  Thermal resistance is much higher with that TO-220.  Someone at the factory has decided to cheap out.  If you ever get to the point you are repairing these yourself, replace those with a higher current TO-247 type.  Is that darkness at the center of the board some some component that blew up or did something drip onto it? Looks like the switch mode inductor got trashed. Could be nearby lightning.
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