Ramping up 3hp pump motor [RE-wrenches]

Christopher Freitas - OutBack Power cfreitas at outbackpower.com
Mon Sep 17 22:14:50 PDT 2001


I have had good luck with a product from Allen-Bradley called a 
"starting torque controller" or STC.  They are made for use on conveyor 
belts and with machinery to reduce shock loading etc.  They are simple 
and have an adjustable ramp time period plus on some features like 
minimum off period delay.  

I have used them with Trace SW series inverters several times and with 
various generators to start large pumps and air conditioners.  I 
recently noticed they have changed a few of the models,  so the part 
numbers I used are no longer listed. 


Christopher Freitas
OutBack Power Systems, Inc.
cfreitas at outbackpower.com  www.outbackpower.com
Tel 360 435 6030  Arlington WA USA

 
Jeff Yago wrote:
> I have not used an variable speed motor drive (VFD) on an inverter
> yet, but have lots of past experience with VFD's.  Most units for over
> 1 HP are designed for 208,230, or 460 volt, 3phase input. Since they
> are mainly sold for energy savings market these days, as operating
> pumps and fans at 90% there full speed their can save over 30% of
> electricity with little change in performance. Under this 1 HP size
> usually does not provide energy savings that can offset the high cost
> of installing a VFD, so the higher quality units usually start at 5
> HP.
> 
> Be sure motor driving your pump is designed for VFD application as
> there have been lots of motor failures due to motor insulation
> breakdown from voltage spikes or bearing failures.  Same "energy
> saving"  motor designs also overheat at lower RPM powered from VFD.
> 
> Suggestion:  Instead of using a standard VFD which have lots of
> expensive program features you will pay for but may not use for your
> application, why not install a "soft start" device?  It has same
> function as the slow ramp up you get with VFD's but not all the rest.
> 
> Jeff Yago
> Dunimis Technology
> 
> 
> 

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