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Solar hot water pumps, - PV array sizing & BLDC pump

Posted: Mon Jun 23, 2008 12:29 pm
by bobc
A colleague at work has put a PV powered electric pump on his roof mounted solar heating array. From ebay he got an array of parts including a small BLDC pump and a £50 PV array (12W).
It didn't work - the array voltage just collapsed with the pump wired in. He was going to buy a bigger PV array, but I suggested that the problem might be tha pulsed current taken by the pump & that a capacitor might solve the problem. To my great surprise, I was right! A 2200uF capacitor across the output & it pumps like billyo - saving him a further £50 bill for more solar cells.


Posted: Wed Jul 02, 2008 1:55 am
by Deker
bobc says "a small BLDC pump"

Whats a BLDC pump, Bob ?


Posted: Wed Jul 02, 2008 9:49 pm
by bobc
BLDC = brush less DC motor

Posted: Thu Jul 03, 2008 3:48 pm
by MalcolmB
Hi Bob
So is the pump being driven without a controller? Brushless motors are usually three-phase aren't they. How are the individual phases connected to the array?

Posted: Wed Jul 09, 2008 3:44 pm
by bobc
Hi Malcolm
The pump runs from a nominal 12V DC - it has internal electronics to do the commutating. It's a cheap 12V pump from ebay intended for automotive use.
It is just stuck straight across the PV array. The array output can go up to 17V on load I think, but car stuff is designed for 14.4V continuous & 42V surge so it should manage. The PV array has quite nice gentle supply characteristics ;^)

Posted: Wed Jul 09, 2008 10:00 pm
by ChrisB
What a cracking tip Bob .....nice one