Actually soft start is not a good thing for submersible pumps. They need to get up to speed very quickly to produce the film of water between the thrust bearing plates. The longer it takes to start, the more wear on the thrust bearing.
A Cycle Stop Valve will give you a mechanical soft start and soft stop, which eliminates any water hammer without slowing the start up RPM of the pump/motor.
Not to be smart, but you often mention using downsize wires to give that 'soft' start - maybe you could call it a 'slower' start? . I know a true soft start is designed for very large 3 phase motors and it really is a step up slow go. Also, as to a three wire motor, those smaller wires might defeat the better start torque need in grit. You mentioned earlier using a large HP control box to try and get a stuck motor started. Interesting to me that Franklin 'deluxe' control boxes, with or without the contactor, are rated 1 OR 1.5 HP. Probably just a 1.5 box that gives the smaller motor a bigger kick.
So to answer ody99's question above, I don't know of any soft starter for less than a 5 HP 3 phase motor. And I don't think anyone would put it on a well pump. More for a shredder or a oil well pump.
At least for Valveman, here is an intriguing link:
http://www.eng-tips.com/viewthread.cfm?qid=256819 It is about the failure of a kingsbury bearing in a huge submersible pump.One poster says the motor must be up to 1/2 speed within 2-3 seconds for preservation of water or oil film.
And most interesting as to the CSV, it is said that the best situation for the bearing is to start against a closed outlet. Interesting that the pump that failed, [the point of the thread] was being started against a 20% closed outlet. Also they discuss the manufacturers insistence that there be intermediate check valves - a source of much debate here in this forum. Mfg. insisting that it preserves the thrust bearing. INteresting!
Finally some amazing trivia:
Success of the Kingsbury bearing[edit]
Kingsbury would eventually run his own business with the Westinghouse Machine Co. building his bearings.
[2] This allowed him to actively pursue applications for his newly patented thrust bearing. His first chance came when the Pennsylvania Water and Power Co. gave him the opportunity to demonstrate his bearing on their power generator at the
Susquehanna River.
His first bearing was a failure as it was immediately destroyed by
Babbitt wiping.
[2] Fortunately for Kingsbury, the
Pennsylvania Water and Power Co. gave him a second chance. His bearing succeeded this time, and worked flawlessly for the next 25 years. When it was inspected after 25 years, there was so little evidence of wear that it was calculated that the bearing would last 1,300 to 1,700 years.
[2] The same bearing is still operating smoothly today.
[4]
