DC sub pumps [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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>....Many of my customers do choose to go with AC sub pumps
>especially since the advent of the Grundfos SQ series of pumps (variable
>frequency for no startup surge).
>
>Dave Palumbo



Wrenches with pipe wrenches,

Beware of terminology shift -- The new breed of "DC" pumps with 
brushless motors are NOT purely DC pumps. This applies to our 
Etapump, which has a controller up-top that takes DC power, does 
matching tricks, then sends 3-phase variable-frequency AC down to the 
pump.

This is a radical break from pure-DC pumps that use brush-type 
motors, and should not be classified under the same heading.

I would call it DC-powered system using an AC motor. The quickest way 
to make the distinction is to call it a "brushless DC pump".

"Brushless" not only means no brushes, but also that the motor does 
not need to maintain air in it, nor a 100% perfect seal. In fact, it 
runs with water inside it by design, so there is no critical seal. 
Most reassuring is that the motor structure is based on the 50-year 
proven reliable design of conventional AC submersible motors. The 
only difference in the motor is the windings, the presence of 
permanent magnets, and beefier bearings to handle the helical rotor.

Windy

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