Electric water pumps (was) alt charging cont sw

[Shannen Durphey]

Greg Hermann wrote:
> 

> >> For any sizable auxiliary drive loads, a mechanical drive is way more
> >> efficient than an electrical one.
> >>
> >> Regards, Greg
> >
> >But, isn't it inefficient to spin all those things at engine RPM rather
> >than a constant RPM?  Seems like a pump/compressor that has to work over
> >a 10:1 input speed ratio wouldn't be as efficient as one designed to
> >work at a constant RPM.  Like A/C, and esp power steering.  If those
> >were designed to run w/electric drive at constant RPM maybe they'd be
> >more efficient.  Especially if you had a dual voltage alternator and ran
> >the accessories at 100V 3phase.  maybe?
> 

> 
> For the power steering pump, I suspect that a variable displacement, vane
> type pump (or swash plate type variable displacement pump, if you wish)
> would give the variability you want for less weight, more simplicity, and
> greater overall efficiency than an electric drive.
> 
> There are variable displacement refrigeration compressors available
> (usually screw type),
GM uses V5 variable displacement compressor on many late model cars. 
Also, 96+ GM pickups use PWM controlled bypass solenoid on PS pump,
full assist at low vehicle speeds, none at high speeds, electrical
failure causes full assist at all times.
Shannen

> but, and this one is based on having done some
> serious refrigeration design work, I think the simplest solution to the AC
> compressor would be to run a regulator valve on the suction line (known as
> an evaporator pressure regulator in the trade). One of these valves gives
> you modulating control over the compressor capacity, rather than just
> bang-bang, on/off control, just by letting the low side pressure to the
> compressor drop well below the pressure in the evaporator (thus reducing
> the compressor's VE. under light load and/or high compressor speed
> conditions)

> >
> >--steve
> >
> >--
> >Steve Ravet
> >ARM, INC
> >steve.ravet at arm.com
> >www.arm.com