timing switching to reduce startup surge

jonr

Exactly when an inductive load is switched on effects the peak current drawn over the next half cycle.   Perhaps non-intuitively, switching an inductive device on while the AC waveform is at a voltage peak significantly reduces the peak current flow.     Has anyone looked at using this to reduce startup surge for a motor?  For example, a pressure switch on a well pump might be connected to a "peak switcher" box and then to the pump.

BB.

Jon, do you want to ask this question in your other thread? They are closely related and you may splat Q&A's across two threads (discussions).

And details help... For many devices, there is an "unloader" of some sort that reduces loading during startup (an air compressor that dumps air to have "zero" back pressure until pump is up to speed--Water pump that opens re-circulation/dump valve to prevent back pressure, or even continuous run--Start the motor once, then use unloaders to regulate pressure, etc.).

-Bill

jonr

I think they are pretty separate.  I'm interested in the specific technique above, not a general discussion of preventing inverter overload.

Dave Angelini

You posted to try the Pentek VFD, am I right?  VFD is the way to go. I have used the Schneider VFD's and they work fine.
That is the specific technique as you say.  Am I missing something??
 Most people have no clue about this  stuff and they just expect it to work. Big inverter system and no problems.
I get it that it is not cheap, but there is nothing new here.  I have been doing this for clients who do not want problems or just expect it to work correctly.

jonr

I agree, a larger inverter or a VFD is a simple solution - although it might cost $1000.   But I find alternative techniques interesting and potentially much less expensive.