Motor soft starters and VFD for off grid

This isn't by any chance a Jacuzzi or older Ingersoll Rand compresor ?
They are the only one's I know of that spec a high RPM like that, a very short stroke reciprocating pump.

 

They are probably a copy of an old IR compressor design.

 

I got in some graphite rods I ordered. The resistance is much lower than I thought it would be. So a graphite resistor would have to be pretty lon to get the resistance I would need.
At least they were really cheap, like $2.

I tested the unloader on the mag clutched 2hp 4 pole motor powered compressor.
It runs up to 7.5 amps at shut off pressure. Opening the unloader lowers compressor draw to 4.5 amps. Which is more than I would have liked to see.
At shut off pressure the cylinder head is about 240°F according to my flir i7. Opening the unloader only cools to down to a minimum temperature of about 180°F after running for 2 or 3 minutes. After 30 seconds it only cools down to 220. And 210 after a minute. In a 70°F environment. It doesn't cool down as fast as I would like.
I do like that it runs a .95 power factor.

 

What is the equipment you are running on air?
And can it be substituted for electric ?

 

Plasma cutter, carbon arc gouging both of which use air and electric. Also a paint gun, charge the air tank on my suburban, cleaning stuff, blowing out water lines draining hot water heater and nail guns, other little tools that ibalso have electric versions of. My smallest 120v air compressor can easily power my nail guns. I mostly use electric stuff where I can.
I would say tires but I have been experimenting with filling them with a 50/50 mix of R-404a and CO2.
With the sand blaster I have had everything going, gas plus electric totaling 5hp gas plus about another 5hp of electric. Real sand blasters use a screw compressor driven by a 50hp diesel engine.
For on grid operation I would like to be able to run all of them off from one to code 30 amp clothes dryer circuit. I was looking at putting in at least one more 30 amp circuit for air conpressors.

 

You've got a lot of heavy stuff gong on ,(a bit envious ) .You might consider larger tanks.

 

Figured out how to put a larger pulley on a 3.2 inch go cart clutch/pulley.
I found an unfinished stamped sheet metal tractor pulley at none other than tractor supply. It's a pulley blank with just a big hole in the center. I think you weld, clamp or bolt them to a shaft or gear on a tractor PTO or something.
All I had to do was center the pulley and I put about 8 nice tack welds around the edge of the 3.2 pulley to the inside of the 6 inch pulley.
Full power starting the 1hp 4 pole motor with hard pulleys was drawing up to 15 amps. The go cart clutch softened the start to 9 or 10 amps.
Note: the go cart clutch needed a much weaker spring to work on the 1,800rpm motor. On a 2 pole 3,600rpm motor they are drop in and go, as long as you only need a 3.2 inch pulley because that is the only size I could find.

 

How about some kind of a torque converter , like there is in an automatic transmission?

 

I may try a comet clutch which is kind of a variable clutch or torque converter. But it would take a much larger 2 belt system.
Fluid-filled ones are typically only 70 to 85% efficient and they are kind of expensive.
And as far as I can tell both of those types of torque converter are used with 3,600rpm and up motors. I have found 1,800rpm motors are far superior to reducing inrush. They just don't seem like they would work well together.

 

Wouldn't it be great if one could use a wind mill to make compressed air.
If you had a large enough reservoir, even low pressure can be a contribution like the first stage of a compressor .(40psi)
Providing of course you have the wind to justify the investment..
I might do something my self some day just to see what I can expect out of it , I've got plenty of spare tanks to play with.

 

This is the wind capital of the United states.
Air compressing wind mills were common around here to pump deep water wells back in the day.

I did some more fine tuning with my 2hp 4 pole motor.
Playing with the capacitors this time.
Going from a 600uf start capacitor down to a 408 to 340 reduced free spin starting amps from 14 to 15 down to 11 to 12 amps.
I didn't notice any difference in 700uf or 500uf. I didn't even think my 408 to 340uf capacitor would work.
I am assuming starting torque is reduced, so swapping in a smaller capacitor on a motor started under load could end badly for the motor, unless you have way too big of a motor for your application.

 

Interesting development, on my soft start test rig I killed one of the 30 amp 2 pole switches on the resistor start side.
There are two double pole single throw switches, one sends full power, the other sends power through resistors or inductors or whatever I'm testing before it goes to the motor so I can switch to full power in a "closed circuit start transition".
I have used a lot of these switches on lots of off book applications and never had one fail. Maybe I got a bad one.

 

Decided to try and fine tune my resistor start. I have an 8 amp rheostat I am going to uses as field control on my emp resistant alternator welder. Not very cheap.
I replaced one of the 5 ohm resistors with this rheostat. Turned it up to 6 ohms, started the motor. Kept turning it up untill i got the speed and amp draw i was looking for. If I use a total of 15 ohms the inrush is largely eliminated.
Found some 7.7ohm resistors and ordered them.
So the resistor start looks like it will fall some where between 10 and 15 ohms.

 

The implementation has been a little slower than I would have liked.
The 1hp air compressor with the go cart clutch has been up and running the longest, I added a time off delay so it doesn't build up to 5 amps then shut off like a normal compressor, now it will build up to max pressure where it reaches 5 amps, unloads drop down to 2 amps then turns off.
with the 2hp electromagnetic clutch compressor I have just been full power, free spin starting the motor and engaging the clutch with a time delay not using the resistor start yet, it does have an unloader, I need to get another time delay and wire it all up.
I have ordered another 2hp 4 pole motor and go-cart clutch for my garage compressor on a skid.

 

Harbor freight has a special on 2hp 1800rpm motors. They normally don't have 2hp 4 pole motors. Just a 1hp.
$169 I think was the cost.

 

I have modified another gocart pulley to go on a 4 pole motor.
Pretty much like I did for the 1hp 4 pole compressor setup.
Took out the spring, replaced it with a much weaker spring. My spring starts to engage the clutch at 200 to 300 RPM, the go cart clutch setup for a 3,600+ RPM gas motor starts to engage some where around 2,000 to 2,400rpm.
It actually works really well on a 2 pole electric motor.
Then welded a 7 inch tractor pulley to it, because the 3.4 inch go cart pulley doesn't turn the compressor very fast when using a 1800 RPM motor.

Next time I have a few days off I will install it.
Just have to redrill the holes and power factor correct it.
Might need to find a longer belt.

 

Looks like I will have a deep well irrigation pump to power up.
The pump had its own 3 phase service. These motors can be wired for 480 or 240v power.
Looks like I will be using a VFD since I'm not paying to put the irrigation pump on its own service.
I need to go back and get a look at the name plate on the motor.
It will take about 150' of wire to get single phase from the house to the well.
I want to put it on a VFD for a few reasons.
1 the cheapest 3 phase generator I can find that might be able to power it is $5,000+.
2 the VFD will eliminate start up inrush.
3 being able to run the motor at reduced speed, assuming it doesn't have to run at full speed can easily cut its power demand in half.
4 I don't want to pay $50 to $100 per month just for 3 phase service.

 

Id buy a real well Grundfos & not worry the VFD stuff , ever .

 

I believe that this kind of pump is motor driven from the surface and the pump is submerged and driven by a shaft.
These things can bring up to a few hundred gallons per minute to the surface.
I don't have to have that much water so if it's shot I will look at the cost of repairing what's there and adding a VFD versus ripping out the old stuff and installing a grundfos pump.

 

I'm looking around on ebay since they allow people to sell new and used junk.
I have not been able to find exactly what I saw but I know they are real common around here and they are old.
Looks like most of these irrigation motors have 3 things in common.
1 All or virtually all appear to be 460v only.
2 around 90% I have seen so far are 4 pole (1800rpm).
3 they're pretty expensive.

Based on what size I'm looking at should only be around 10 to 15hp. Looks like the land was used more for live stock than growing crops. So no gigantic 100+ to 500hp irrigation pump. Pivot irrigation uses multi hundred horse power wells.
Water pumps for live stock can be a tiny fraction of the size of what's used in pivot farming.