Ramping up 3hp pump motor [RE-wrenches]

[Jeffrey Wolfe, Global Resources]

I've never used either of these devices on an inverter (although each of 
them basically IS an inverter), but have used many variable frequency 
drives in standard utility applications. Good drives have adjustable ramp 
up (accel) and ramp down (decel) parameters that can be adjusted on the 
circuit board through potentiometers. you can get a very clean ramp up with 
this. Basically, this is what a Grundfos SQ and SQ-E have built in. The SQ 
has a "soft start unit" and the SQ-E has a complete VFD, (non-field 
programmable, I believe).

This SHOULD work. Tough to guantantee it the first time though, as it's a 
big chunk of change if there's a problem... Problems to watch for on any 
drive (on or off-grid) are electrical "noise" (harmonics) and the control 
signal frequency. The harmonics can be filtered if they cause a problem, 
but the filters can cost as much, or more, than the drive. The line signal 
frequencey can usually be adjusted on the drive (depending upon make and 
model) if there is any kind of problem with it. (Sometimes the signal, 
which is sent as a high frequency wave on top of the AC from the drive to 
the motor, I believe, can cause the motor to set up a sympathetic harmonic 
vibration, which can be noisy, and eventually damaging.)

But really, most drives work fine out of the box, "trust me".

Depending upon how deep you want to get into it, you might talk directly to 
ABB, a manufacturer of variable speed drives. They might be able to fairly 
easily customize a unit for you with no AC front end, taking power straight 
of the batteries. You'd end up with an oversized unit this way, as their 
units are basically sized based upon a high input voltage, and you'd be 
giving them a lower input voltage. But this would divorce it from any 
possibel inverter interference / interaction problems.

ABB is very interested in RE, they are making some large inverters for some 
large RE project and products (wind and solar), and have shown a 
willingness to work on some "special projects" without cahrging ridiculous 
sums, if it's an area they want to do more in. We're working ona project 
with them right now on a large off-grid inverter. (Can you believe there is 
nothing on the market right now, that we can find, for a 20 - 60 kW 
off-grid inverter?)

Jeff

Jeffery D. Wolfe, P.E.
Global Resource Options, LLP
A Woman-Owned Limited Liability Partnership
Trace Certified Dealer - Charter Member
Bergey Windpower Certified Dealer
4 Kibling Hill Road
P.O. Box 51
Strafford, Vermont 05072
800-374-4494 Toll Free
802-765-4632 Phone
802-765-9983 Fax
global at sover.net
http://www.GlobalResourceOptions.com



On Wednesday, August 29, 2001 3:25 PM, Holt Kelly [SMTP:hkelly6 at msn.com] 
wrote:
> Hello all,
> I am designing a system that has a 3hp pump motor(sub)that homeowner
> wants on the battery back-up. Grid-tied, 5548/D power panel, 16(?)
> PVX12255 AGM, about 3k PV.  I'm looking at either a Variable Frequency
> Drive or a Smart Motor Control. Wondered if anyone had thoughts,
> experience with this.
>
> "We do not inherit the earth from our parents. We borrow it from our
> children."
>
>
> Holt E. Kelly
> Holtek Fireplace & Solar Products
> Waco, TX.
> hkelly6 at msn.com
>
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