Help me select soft start for a trial test for a pump

[fastline]

I am working to reduce both the torsional abuse and inrush current on a typical submersible pump motor. I am very much a fan of easier starting to protect equipment. I would normally want to reach for a 3 phase setup with a VFD but unfortunately with a 1HP pump, 3 phase is very uncommon, meaning even if i went that route, finding a replacement in a pinch would not be likely.

I have worked with hundreds of submersible pumps and know them well. I know that soft starts are becoming more and more common, however their design criteria is all over the map. The motor I want to test with is a common Franklin '2 wire' motor. This motor design does not use a start cap, but rather some electronics internally. I have a hunch it is a triac feeding a start winding but never got one apart because they are 100% potted.

Because I can find no one that has ever done this, my best course is to setup a test pump and monitor the start up carefully to evaluate. My target is to get inrush down to right at FLA. If the 2 wire until cannot be made to work, I may run further testing with a 3 wire, which does use a top side capacitor start. There are also some 2 wire capacitor start motors but those are literally junk as they submerse the capacitor attached to the motor and they 100% fail.

 

[ptonsparky]

Use Franklins control.

 

[ptonsparky]

Increase length of wire or decrease the size to minimum.

 

[ptonsparky]

I use a 3 phase 1.5 hp on a VFD. Fourteen years old and counting. Maybe I should worry. Tomorrow maybe.

 

[petersonra]

get a pump with a dc motor.

 

[GoldDigger]

For off-grid (solar and/or wind) sites where both total power and peak energy are limited, the gold standard is submersible pumps made by Grundfos. They have models which include a variable speed drive for a single phase pump.
They are correspondingly pricey, but they do the job.

 

[fastline]

For off-grid (solar and/or wind) sites where both total power and peak energy are limited, the gold standard is submersible pumps made by Grundfos. They have models which include a variable speed drive for a single phase pump.
They are correspondingly pricey, but they do the job.

I would agree, however, even in talking to a Grundfos "engineer" (not), they don't even understand what they are selling. It would seem they stuffed a ton of logic into the motor housing and throw it down the hole. Just not a wise idea IMO. Sort of like putting the ECM for your car engine inside the actual engine. So when you get tapped by any voltage transient or EMP event, you are stuck buying that all over again.

I am looking for a way to scrub inrush on a more standard motor. Even DC pumps are not that popular unless for the "doom day" people or farmers running stock tanks.

Something being missed is potential galvanic corrosion of a DC based system. I am certainly onboard with BLDC tech, but I cannot ignore industrial standards running AC, even if not true sine wave. A DC motor and cord set thrown in the water sounds like a maint nightmare to me.

I am aware of some of the stuff by Franklin, which is some sort of VFD variant for 1 PH motor, but again, they are extremely proprietary and I have one on the shelf that was given to me that supposedly failed, no one works on them or knows how, and the customer bought another for $2K.

 

[herding_cats]

most single-phase speed controllers are a wave-clipping device and generally bad for the windings.

If you can redesign it with a DC motor and a controller at ground level that's the best setup.

Also check out the single-phase soft starters from Hyper Engineering or "sure-start" (same thing)

 

[kwired]

I would agree, however, even in talking to a Grundfos "engineer" (not), they don't even understand what they are selling. It would seem they stuffed a ton of logic into the motor housing and throw it down the hole. Just not a wise idea IMO. Sort of like putting the ECM for your car engine inside the actual engine. So when you get tapped by any voltage transient or EMP event, you are stuck buying that all over again.

I am looking for a way to scrub inrush on a more standard motor. Even DC pumps are not that popular unless for the "doom day" people or farmers running stock tanks.

Something being missed is potential galvanic corrosion of a DC based system. I am certainly onboard with BLDC tech, but I cannot ignore industrial standards running AC, even if not true sine wave. A DC motor and cord set thrown in the water sounds like a maint nightmare to me.

I am aware of some of the stuff by Franklin, which is some sort of VFD variant for 1 PH motor, but again, they are extremely proprietary and I have one on the shelf that was given to me that supposedly failed, no one works on them or knows how, and the customer bought another for $2K.

That is the problem with those - they are a definite purpose drive and along with it comes a price tag. They typically can be programmed to run single phase two wire or three wire pumps or three phase pumps. They already have the logic built into them to do everything needed for a water pumping system with just a few variables that are selected in the field and all you need is their pressure transducer, which usually is also included as an input device.

Three phase motor and a general purpose drive is a lesser expensive way to go plus you need pressure transducer and either a PLC to process things or many general purpose drives are now have some PLC functionality and in particular PID functions for varying the speed to what the input is registering.

 

[herding_cats]

If you need a basic PLC and some basic logic to drive it I can help. Or just basic switch design to connect to a drive.

 

[ptonsparky]

We are all entitled to reinvent the wheel if we desire. I've attempted a time or two.

 

[Jraef]

Use Franklins control.

I’m pretty sure Franklin voids your warranty if you don't use their controller.

Soft starters for single phase motors are very problematic anyway. It usually becomes a race to failure for the motor or the soft starter. I’m not sure what Franklin is doing with their unit to get around the rotation issue without a cap or a VFD or a third wire down hole, so anything you add to it not knowing is likely going to be a problem somewhere.

 

[synchro]

At the links below are a description of Franklin 2-wire motor starting, and a patent on its operation.

https://franklinwater.eu/media/320268/4inch-2wire-Motor-Function-Description.pdf

https://patentimages.storage.googleapis.com/dc/b1/b0/59b83395dbf1a4/US4325012.pdf

I believe Franklin 2-wire pumps have traditionally been split-phase motors like in the above documents, although I've seen they also have 2-wire PSC motors with internal capacitors like other vendors do. Split-phase motors rely on a relatively high resistance starting winding, which together with the winding inductance produces a phase shift necessary to create a rotating magnetic field component to start the motor. This is cheap but inefficient, and the starting current is quite high (several times the FLA).
Personally, I would not try to mess with Franklin 2-wire split phase pumps using soft starts or VFDs. Even though they may have an RC snubber across the TRIAC, the fast risetimes of soft-starts and VFDs might cause issues with the TRIAC device.

It could be interesting to run a 3-wire PSC pump that has an external capacitor which remains connected while operating, and see what voltage is developed on the auxilliary winding. Preferably, you would also measure the phase shift of the voltage created across the auxilliary winding by the capacitor with a 'scope or other means. If it's close to the applied line voltage on the main winding, then you might try a VFD on the 3-wires (with no capacitor) to see how it behaves. The VFD will provide a 60 degree phase shift on the auxilliary winding relative to the main winding. Of course you are on your own as far as how effective and reliable this might be.