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upping HP of motor

junkhound's picture

Curious what folks here would say to this:


need a 20 HP motor

have a 184 frame 1750 RPM 5 HP (240V, 60Hz, 26A) single phase motor.

Can I run it at 3600 rpm (or higher) with an inverter and use an old furnace fan to 'supercool' the frame to 'push' the motor to produce 20 HP?

Have been told this can be done.

No. (post #208060, reply #1 of 11)

No. Why do you need a 20 HP motor?

Try it.  Post videos of the (post #208060, reply #5 of 11)

Try it.  Post videos of the results.  I suspect that if you increase the current in the motor, the magnetics will saturate long before you reach 20 hp.  Then the blower will make a short lived flamethrower out of the motor.

And come on you have "a five (post #208060, reply #2 of 11)

And come on you have "a five hp motor"?  I bet you have a shed full of em.  Just chain four of them together bada bing 20hp.

The reincarnation of TIm the (post #208060, reply #3 of 11)

The reincarnation of TIm the tool man Taylor.  More power.  You should film it as it might go viral on Face Tube.

Off topic, if you want to drive your kids crazy, ask them about Face Tube or Space Book or My Face in front of their friends.

If you insist on trying this....... (post #208060, reply #4 of 11)

You should up the RPM to 7200 and be sure that the setup is water cooled.

359498071_640.jpg50.2 KB

Come on, you know better than (post #208060, reply #6 of 11)

Come on, you know better than that.  At 120 Hz the impedance of the windings will shoot upward and you'd have to quadruple the voltage.  Losses, as a percent of total power, will go up due to higher eddy currents in the laminations.  You might be able to generate 20 HP, but not for more than about 30 seconds.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Shop Vacs (post #208060, reply #7 of 11)

If you use the math that manufactures use for shop vacs and you already have 20 hp.

If you use the math that (post #208060, reply #8 of 11)

If you use the math that manufactures use for shop vacs and you already have 20 hp

LOL, so true. 


Here is the setup as it is now, only 10 HP from the 5 HP motor, still at 60 Hz.  Have run at 10HP for a few years.  Mostly worried about destroying the pump at 3600 rpm, or having to replace the valves every time I'd use it at 8 GPM, 4000 psi.

pic below of the motor/pump as now configured - running at 10 HP powering mTm 4kpsi, 4 gpm pressure washer that originally had a 11 HP Honda engine. Old furnace blower ducted to shroud around finned case motor and ducted thru windings. Motor runs at < 20C rise on the case, have not measured the temp of the windings.  Have run this for 5-7 hours at a time 5 or 6 times a year for the last few years, no problems yet.

Thinking of going to fatter nozzle and upping the flow to 8 gpm.

It draws 48 A/240V now at 10 HP (48A includes the 1/3 HP cooling blower), need to run a 6 AWG feeder if I go up to 8 gpm. I cannot, or course, even run it off my buried extension cords, gotta use a regular 60 branch circuit - even the 50A old range outlet being used now gets warm without being in the airflow <G>

I'll put more technical specifics on plans later, I've gotten a 'kick' out of some comments on the holt elec board replies from 'gurus'. Did not give them a pic originally either, just a 'can this be done' question.

one of the 'trick' questions was how to do this and what were the concern that  I used when I taught some EE courses at work,

Hint: For 20 HP, gotta build my own 2 phase inverter, one phase for main winding, second for the start winding to be able to eliminate the capacitors.



That's very interesting! (post #208060, reply #9 of 11)

I was going to say can't be done because you mentioned an inverter.  All motor controllers I have used require a three phase motor.  I don't think you will hurt the pump at 3600 rpm if it was direct coupled to the engine before.  Still... I  am not to confident you can get 20 hp.  Are you going to run the motor with some power to the start winding for a little extra umph?

Are you going to run the (post #208060, reply #10 of 11)

Are you going to run the motor with some power to the start winding for a little extra umph?

Yep, that is what I meant by intent to build a custom 2 phase inverter , using the start winding as an unbalanced '2nd phase'.  To my knowledge, will have to build inverter from scratch (but using off the shelf motor contorl chip), as there are no unbalanced 2 phase commercial inverters like this I know of - obviously easier to buy a 3 phase motor if you have 3 phase available or want variable speed.

The original pump application with Honda 11 HP engine was belt drive reduction for 1800 RPM pump speed.

I would divert some of the (post #208060, reply #11 of 11)

I would divert some of the low pressure water through a radiator in front of the blower for a slight bit cooler air over the motor.  Variable speed would actually be a good idea to throttle down the motor.  You could have a flow transducer and pressure transducer to control the motor speed. Most inverters will run single phase input, but you don't get full power output.  You would need a heck of an inverter to run a 20hp motor on single phase input, probably one rated about 60hp.  We're talking serious input amps too.