ThanksNo!
I was very likely to stop just with the above answer, but let me continue a little. With soft starter you can gradually increase to nominal speed(50/60 Hz) whatever is the line frequency. With VFD you can run the motor at the frequency you want continuously or you can change it continuously to adjust (in your case) output flow or pressure or whatever you would like to control on your pump.
mdim is correct, they are not the same thing.
There is such a thing as a soft start. It's not a full blown VFD, but only a soft start that ramps up to line frequency/voltage on start. I have a couple at work on 75HP motors, the application does not need full capabilities a VFD can provide, so a considerably less expensive soft start was used instead of a large VFD that could cost 5 thousand dollars or more.
And most (some?) soft starters come with mechanical contacts that bypass the VFD after the starter has done its job so that there are no additional VFD losses.
Please send me part numbers of soft starters 10x cheaper than a VFD.But a VFD is, for the most part, 5-10x more expensive than a Soft Starter, so if a machine does not need to be changing speed, a Soft Starter is more economical.
[/LIST]
Please send me part numbers of soft starters 10x cheaper than a VFD.
A VFD can be setup to be more efficient than a soft start+DOL even at line frequency, when the load is less than the nominal load.