Should I Buy This 10HP Motor? - Page 1
Forum section: electronics / beginners

author: electromateria
author_rank: Regular Contributor
timestamp: November 03, 2020, 06:06:02 am
content: I'm looking for a good all around motor that I can use in my workshop.I want something that can run custom tools that I make (powerful sander for metal, industrial grinder, custom mitre saw to cut steel, etc).Here it is, the price is $250 CAD.Is this a good motor for my needs?Any there any special power requirements to run it?Is it easy and inexpensive to control the speed?Is single phase better than 3 phase?

author: bob91343
author_rank: Super Contributor
timestamp: November 03, 2020, 06:12:36 am
content: That's a lot of power. 230 V at 40 A is almost 10 kW input.I would think a smaller unit would be more than adequate but then I don't know what you are planning. Also it's rather slow, only 150 r/m so wouldn't be fast enough for some jobs. Most power tools run at higher speeds.

author: electromateria
author_rank: Regular Contributor
timestamp: November 03, 2020, 06:25:25 am
content: Quote from: bob91343 on November 03, 2020, 06:12:36 amI'm still really new to electronics, I don't know anything about kW. I'll do some research into the costs, thanks for the tip!I can use gears / sprockets to increase the RPM if a machine needs it. I should be able to make custom gears soon (hopefully).The motor isn't really 200 lbs is it? I was expecting maybe 45-50 lbs at most. That might be a deal breaker for me.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 06:26:47 am
content: Well for a 10HP motor there's no way around nearly 10kW input, although the current should be quite a lot lower under lighter load. It's unusual to see such a large motor that is single phase too, most in that size range are 3 phase.It looks like a nice motor but it's very large for home machine tools kind of use. I would think you'd want to go with a 3 phase motor and VFD to get variable speed and easy reversing. 10HP also seems very large, even the biggest band saws and drill presses and such at my friend's shop are around 3HP, most less. I think even the big manual metal lathe is less than 10HP.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 06:32:45 am
content: Quote from: electromateria on November 03, 2020, 06:25:25 amIMHO if you're really new to electronics and don't know anything about kW you probably shouldn't be messing with a 10HP motor. That thing will tear off a limb without even slowing down. Yes 200 lbs sounds about right for 10HP. I have a 2HP motor that is about 50 lbs, and mine doesn't even have a big gearbox on it like that one does. Look for something in the 1-2HP range, 3 phase, and get a VFD. Forget about gears, at the shop we converted all the old drill presses, we would remove the variable belt drive contraption and replace it with a single fixed belt and wire it up to a VFD. Much better performance, smoother, quieter, mechanically simpler and more reliable, much wider speed range, torque limiting, soft start, better all around.

author: george.b
author_rank: Frequent Contributor
timestamp: November 03, 2020, 06:34:25 am
content: Ha, WEG! Their headquarters are in my stateI suppose you'd be removing the reduction gearing, yeah?

author: electromateria
author_rank: Regular Contributor
timestamp: November 03, 2020, 06:45:52 am
content: Quote from: james_s on November 03, 2020, 06:26:47 amQuote from: james_s on November 03, 2020, 06:32:45 amThanks for the tip about the VFD!Apparently where I live the price is 12.8 ¢/kWh. Sounds really cheap! That means 12.8 cents per hour of use right?I need to use it for powering an experimental hydraulic press and other projects. It will need as much torque / power as possible while being reasonably mobile. 200lbs is way too much. Wish I could have all that power without the weightI'm going to take your advice and get a smaller 3-phaseQuote from: george.b on November 03, 2020, 06:34:25 amI'd probably leave it and add gears on machines that need higher RPM. Haven't really thought it through yet though.

author: electromateria
author_rank: Regular Contributor
timestamp: November 03, 2020, 08:35:16 am
content: I've been looking into VFD controllers. They seem pretty expensive, they almost cost as much as the motor itself if not more.Is there any cheap solution?Is it possible for me to create my own very basic controller that can work with a 5 HP motor?

author: Berni
author_rank: Super Contributor
timestamp: November 03, 2020, 08:52:39 am
content: Quote from: electromateria on November 03, 2020, 08:35:16 amYou can if you had the electronics knowledge for it, but whatever you make is going to be easily twice as expensive as a Chinese VFD off aliexpress, and that is without even factoring in any labor to actually design and build the VFD,

author: Siwastaja
author_rank: Super Contributor
timestamp: November 03, 2020, 09:05:00 am
content: Definitely no. A single-phase capacitor-start/capacitor-run motor is a terrible idea in 2020. Actually it's quite a terrible ideaanyway, such large motors would normally run on 3-phase mains.Instead, buy a similar-sized actual 3-phase motor and a VFD for it. Actually if you think this particular motor would offer enough torque and power for your needs, likely a smaller one (say 5.5kW) would suffice given it's 3-phase and ran with a VFD.Cheaper VFDs are available. Used units are available.It's also possible the motor you show requires replacing new capacitors (or maybe the capacitors are missing completely), it also costs to buy proper new capacitors.

author: BlackICE
author_rank: Regular Contributor
timestamp: November 03, 2020, 09:47:53 am
content: You should remove the gearbox to see what the shaft looks like. 10HP is overkill for your use but the price is great if the motor is in good condition with more life in it. It seem to be a cap start cap run 1 phase motor which will take a lot of current to start it up, probably more than 300 AMP! In a normal home that will create a large voltage drop throughout the home, with the lights dimming, and possible crashes and reboots of some devices.I have just added 3 soft start PCB to my 3 AC compressors that lowered the current from 160 to 67 amps on my 5 ton unit. Without the soft start my lights dimmed significantly during startup. I my home has a larger 400 AMP 240VAC service! Most homes only have a 100 maybe 200 amp service.I think a VFD only works with 3 phase motors. A 2 to 4 HP 3 phase with VFD would be much better for your use, but new would cost much more. I have a couple of 2 HP with VFD on a lathe and mill and I like the lower startup current draw and variable RPM.

author: Berni
author_rank: Super Contributor
timestamp: November 03, 2020, 10:17:00 am
content: Oh i completely missed the point about this being a single phase motor. Upon seeing 10kW i just automatically assumed it is 3 phase because in EU most motors above about 2 or 3 kW are three phase.Yeah in this case i suggest you forget about well controlled low speed high torque output. There are VFDs that will run single phase asynchronous motors by feeding it the two shifted phases, but good luck finding one for 10kW. For a good reason too as 3 phase is so much more superior. How well these single phase VFDs work depend a bit on the motor but in general it will only run well in a limited range of speeds, might not really produce that much torque, not run efficient, make a lots of loud buzzing noises etc.The startup current on this thing must indeed be huge too, tho since you are in canada you could probably soft start it by running it on 120V to begin with and switch to full 240V once its up to speed. Sort of like the delta-star starting switch on 3 phase.

author: jpanhalt
author_rank: Super Contributor
timestamp: November 03, 2020, 10:40:51 am
content: Many years ago, workshops had single motors/engines to supply multiple tools, often with an overhead drive shaft and flat belt drives. I would not recommend that today for a several reasons that should not need repeating.Motors are cheap, as are associated controllers. I would buy individual motors (DC or 3-phase) and controllers. If you want a single power source for lighter tools, consider compressed air. A 5 HP to 10 HP air compressor can supply a variety of drills, riveters, grinders, blast cabinets, etc. and do so safely.

author: elekorsi
author_rank: Regular Contributor
timestamp: November 03, 2020, 11:28:58 am
content: Wrong approach to selection of the motor. First you should determine the power, that is needed for your machine and then you select the motor, with correct power rating and pole number.For example, you are mentioning hydraulic press. First you would decide what do you want from it. For example basic for the press is it's press capacity in Newtons, then you would select proper hydraulic cylinder based on that required force and pressure delivered from the pump. You will select your pump capacity based on what speed of hydraulic cylinders you need. And on the end you will calculate how much power does the pump need at specific RPM and FINALLY, with this data you will select the motor.This is 10HP/7,5kW shaft power and as many others have said it's quite a lot for the equipment you are mentioning (sander, grinder, saw) for a typical DIY workshop...

author: Stray Electron
author_rank: Super Contributor
timestamp: November 03, 2020, 01:14:51 pm
content: Quote from: electromateria on November 03, 2020, 06:25:25 am200 lbs is light for a TRUE 10 HP motor. This really is a10 HPmotor unlike the crap that that's sold by HD, Sears and the like that rate their motors by "Developed HP" or "Peak HP" or some other BS lie.My advice is to skip this motor unless you KNOW that you need it. I doubt that you'll ever find a need for this like of power and this will require a special electrical circuit.FYI I have an oldmonsterradial arm saw with a 24" diameter blade that will cut 8" deep in one pass and with 48" cross cut capacity and it only uses a 7 1/2 HP motor.FYI2. There's a reason that large motors like this can commonly be foundcheap, They're impractical for home owners or people that have small shops and, today, there are usually much better alternatives as others have pointed out. A large,single phasemotor is especially impractical.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 03, 2020, 05:04:19 pm
content: A 50lbs 4kW 3-phase motor driven by a VFD will produce same or more torque than this monster without the mains wiring and surge requirements, and seeing you don't know the final application yet, allows you to adjust RPM over wide range (while generating proper torque).Note such a motor is some 10-20% efficient while running outside optimal RPM while a 3-phase one on VFD is easily some 80% efficient over most of the operating range.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 06:14:26 pm
content: Quote from: electromateria on November 03, 2020, 06:45:52 amYes, a 1kW (1,000 Watts) load would cost you 12.8 cents per hour to run. 1HP is 746 watts at 100% efficiency (which you can never actually achieve) so I usually assume about 1kW per HP. This means that at full load that motor would cost you approximately $1.28/hour to run, although the power a motor consumes will be roughly proportional to the mechanical load placed upon it. At no load that motor would probably only consume a couple hundred watts, that will be resistive losses in the windings and friction in the bearings, all of which turns into heat.Motors are heavy, especially big ones, and especially big, low RPM ones! This is a 1725 RPM (4 pole) motor, so it needs to develop twice the torque of a 3450 RPM 2 pole motor to develop the same horsepower. The housing looks like cast iron, and inside there will be heavy iron laminations in the stator, a heavy steel shaft, lots of heavy copper windings, there's a lot of mass there. Note the lifting eye on the top, it is intended to be lifted by a hoist, not something a person would carry around.Regarding VFDs, they are expensive if you just go out and buy a new one, though much cheaper than they used to be. There are deals that can be had on used ones though, I have bought several for under $100 in the past. It's still a reasonable chunk of money but you have to consider the total system cost, and don't forget to value the time you will spend constructing mechanical transmission systems, a non-trivial task when working with several horsepower. Ultimately you will get much better performance using much simpler mechanical systems and a VFD and ultimately spend less money than if you try to go the cheap route and start fabricating fancy mechanical transmissions.

author: electromateria
author_rank: Regular Contributor
timestamp: November 03, 2020, 06:52:00 pm
content: Thanks for all the very helpful replies!! You guys have given me a lot of research to do:mains wiringsurge requirementspole numbermotor capacitor requirementsI'm sure I'll have lots more questions soonI found this company based in BC:https://www.lenmark.com/search?type=product&q=motor&_=pf&pf_t_horsepower=Horsepower_5&pf_t_rpm=RPM_3400%C2%B1They sell all kinds of used industrial equipment. I need to ideally find a company like this based in Ontario so I can pick it up locally.I think I'll try to find a motor that's approximately 3500 RPM / 3 phase / 5 HP. From what I've seen these motors weigh around 100lbs which is.. manageable.Quote from: james_s on November 03, 2020, 06:14:26 pmWhere do you usually buy your used VFDs if you don't mind sharing?

author: bob91343
author_rank: Super Contributor
timestamp: November 03, 2020, 07:50:10 pm
content: If you are near to a company with a wide range of these products, I suggest you visit them and tell them what you are attempting and ask for their suggestions. They want a happy customer and certainly would have the expertise you seek. No sense going it alone when free help might be available. Begin with a telephone call to see if their attitude is a beneficial one.

author: Renate
author_rank: Super Contributor
timestamp: November 03, 2020, 08:02:21 pm
content: The motor is 200 lbs, the reducer is another 100 lbs at least.This reminds me of a phase inverter I wired up for a friend once.It's basically a single phase motor with extra windings to give a three phase output.The size was probably about the same as that motor.When we switched it on (with no three phase load) it sat there sucking up over 100 Amperes for over 10 seconds until it was up to speed.I think that I'd go for something with a softer start and then only when you have an exact use for it.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2020, 08:07:52 pm
content: Quote from: electromateria on November 03, 2020, 06:52:00 pmI bought mine on ebay. Obviously what is available changes constantly but if you keep watching for cheap ones you might find something.I wish I'd seen this thread 2 weeks ago when my friends were wrapping up moving their shop. There was a nice 3HP 3 phase motor in the free pile, I almost grabbed it but thought what am I ever going to do with such a big motor, I already have far too much stuff and my garage is a disaster. You never know what might turn up though, keep an eye out, motors are everywhere, scrap dealers who deal in machine tools and light industrial stuff might have something. Surplus City Liquidators and Surplus Sales of Nebraska are both places I've gotten deals on this sort of thing from in the past, I have not checked their stock recently though and shipping has gotten a lot more expensive than it used to be.

author: amyk
author_rank: Super Contributor
timestamp: November 04, 2020, 01:05:03 am
content: This is what a true 10HP single-phase motor looks (and sounds) like:The 7.5HP version is over 600lbs.

author: electromateria
author_rank: Regular Contributor
timestamp: November 04, 2020, 03:33:25 am
content: Today while driving home I found two 1HP industrial motors and a smaller one on the side of the road. Unsure of the condition.I'll post some pics soon.Quote from: amyk on November 04, 2020, 01:05:03 amI can only dream the motor I buy will sound that incredible. I'd run it all the time just to listen to it lol.

author: james_s
author_rank: Super Contributor
timestamp: November 04, 2020, 03:45:22 am
content: Quote from: amyk on November 04, 2020, 01:05:03 amRepulsion start motors are huge and heavy for the power they produce, I don't think they've been made since the 1950s or so though. Advances in transformer steel and winding insulation resulted in a substantial reduction in size and weight of motors and transformers sometime in the 1970s and much simpler single phase motor designs displaced the complex and bulky repulsion start machines. I do like big antique iron like that though, it would be fun to play with.

author: electromateria
author_rank: Regular Contributor
timestamp: November 04, 2020, 06:24:25 am
content: I hit the jackpot.. check this out guysIt's garbage day and all this was outside one guys house in a bucket and a milk crate. It felt like christmas unboxing this stuff lol.Any idea where those brass fittings are used?I got a 100 amp fuse and a 200 amp, some interesting (gas?) valves, pipe nipples and elbows and quite a few strange items I have no idea what they are.Anyway as far as the 2 main motors:I'm gonna need some help wiring these up (of course)What's the difference between the low voltage and high voltage options as far as performance? If I go with 115 volts instead of 220? The 220 is a 3rd phase power source or something right? If I use 115 do I need a VFC to simulate 3 phase? I'm very confusedI can wire these up with a old microwave power cable right? Can anyone ELI5 which wires get hooked to wear? I just want to run these motors, no need for speed control on them right now.I only have 115v in most of my outlets (I think - haven't tested) I know I have 220 through my oven though.. so I can probably get my brother in law to tap into a wire somewhere and split me off some juice out the the workshop, he's an electrical engineer.

author: CaptDon
author_rank: Super Contributor
timestamp: November 04, 2020, 06:24:09 pm
content: Every question you have posted shows this isn't a project for you. Go figure, if a kwh is 12.8 cents, and yourmotor is about 10KW then it cost 128 cents per hour. You probably don't have 3 phase anywhere near youand if you do you will need to determine if it is 208Y or 240 Delta with a wild leg, all questions we can't answerfor you. Is Canada standardized on 50 or 60hz? Doesn't matter if you use a VFD. Gearing down through theattached gearbox and then gearing back up is a piss poor idea and very wasteful. Use the small motors if youever figure out the voltage and wiring on them for each individual project. Maybe just go to harbor freight andby the machines you think you need, you'll be less likely to kill yourself or blow up the earth in the process.

author: james_s
author_rank: Super Contributor
timestamp: November 04, 2020, 06:36:22 pm
content: That's a single phase motor, it is not suitable for use with a VFD. If you wire it for 240V it will draw half as much current as it does from 120V so if you have 240V available then that is the superior option as you can use thinner wire and the voltage drop will be lower due to the lower current. There will be no significant difference in performance either way though as long as it it is wired adequately. The wiring looks pretty straightforward, just follow the diagram. If you wire it up as shown for low voltage with a standard 120V power cord and plug it in it should start up. I suggest plugging it into a power strip that has a breaker on it and flip the switch rather than just plugging it straight into the wall, that's less likely to result in fireworks if you get it wrong.As for the other stuff, that mostly looks like junk unless you happen to need some particular fitting, it's mostly domestic plumbing stuff. I see a thermostatic expansion valve (TXV) that looks like it's from a central air conditioning system, probably a bad one that was replaced.

author: electromateria
author_rank: Regular Contributor
timestamp: November 04, 2020, 07:12:54 pm
content: Quote from: james_s on November 04, 2020, 06:36:22 pmOk thanks! I think I'll wait for help on Saturday to wire up the motor, just to be 100% sure I do it correctly.Quote from: CaptDon on November 04, 2020, 06:24:09 pmMost motors don't come with a gearbox like the original 10 HP one I inquired about. If there's a gearbox I could just remove it then attach a different setup.I'll ask my brother in law on Saturday, he wires up and programs industrial motor setups for huge sawmills. I heard that if you don't have 3 phase power there's a way to "simulate" it. Is that not true? I'm going to do some serious research on 3 phase tonight if I have time.Buy from harbor freight? That's the cowards way out lol. I want a beast industrial motor in my workshop.. and I demand satisfaction

author: bdunham7
author_rank: Super Contributor
timestamp: November 04, 2020, 07:46:28 pm
content: Quote from: electromateria on November 04, 2020, 07:12:54 pmYou can wire up some capacitors to get a three-phase motor to run on single phase, but it is a crap solution and your motor will have reduced power, reduced efficiency, a terrible torque curve and will probably burn out in short order if you try to use it with any significant load. If you want a variable-speed motor, anappropriate3-phase motor and a VFD is the way to go. If you don't need variable speed, single phase motors are just fine up to 3HP or so, above that you need to worry about a few more things like wiring.The problem with just picking up random motors is that you don't know enough about them. Induction motors can be configured (by rotor resistance and winding design and more) in many different ways depending on their application--they can have torque curves that vary from operating only near synchronous speed--like a bench grinder--with a high breakdown speed (the slip percentage where the torque starts decreasing) of 90% all the way to a motor that produces peak torque from zero RPM. This applies to 3-phase as well as single phase capacitor start/capacitor run motors. 3 phase does not automagically mean infinite starting torque, which some people seem to believe. The advantage of using a 3-phase with a VFD is that you can control speed and in the case where you have a large inertial load, like a very large grinder, you can soft-start it and not overheat the motor. Not burning up is a different issue than having a lot of torque. Motors for a water pumps, bench grinders, table saws and air compressors are all specifically designed for those applications. A PSC motor designed for a fan or fluid pump may totally fail at starting a heavy inertial load. A motor designed for zero-speed starting torque, like some conveyor systems, may be very inefficient and slow if you use it in a saw application. You can't just randomly mix and match and the fact that some motor is a 'beast' doesn't mean it will work for you.

author: james_s
author_rank: Super Contributor
timestamp: November 05, 2020, 01:35:04 am
content: There are a few different ways to create 3 phase power. The easiest and best way is to use a VFD. The other method that was commonly used in home shops back when VFDs were still very expensive is a rotary phase converter. This was similar to a big 3 phase motor, sometimes people used an actual 3 phase motor to build one but you could also buy them ready made and they looked like a motor with no output shaft. You would add some appropriate capacitors to create a phase shift and then get the thing going, some used a small single phase "pony motor" to spin the thing up, then once it was running it would generate 3 phase power across the windings from a single phase input. It worked, but you had to be careful with load balancing, and it would take a big motor, like 7-10 HP to get enough 3 phase power to run a 3-5HP motor on the machine you wanted to power.I think everyone just uses VFDs now, they're superior in every way to a rotary converter.It's true that motors are optimized for various tasks, however quite a few are designed to be fairly universal. The main thing you have to watch out for is motors designed for fans or blowers typically do not have a built in cooling fan as they are designed to operate within the air stream of the fan they are driving. The next biggest difference is starting torque, motors designed to power air compressors for example are typically capacitor start, capacitor run types (they'll usually have two humps on the top for the capacitor housings) but that doesn't apply to 3 phase. There's a first time for everything but I have not yet burned up a 3 phase induction motor by repurposing a random motor for some other application.

author: electromateria
author_rank: Regular Contributor
timestamp: November 05, 2020, 08:28:03 am
content: Quote from: james_s on November 05, 2020, 01:35:04 amReally cool!! I just spent some time researching the rotary converter. I still don't fully understand how it works, but I find it really interesting! I'm going to do more reading on it tomorrow.Theoretically - say I were to stick 3 plugs into a power supply, then direct those "three random / uncontrolled phases" to a control unit that syncs up the cycles, wouldn't that output some kind of 3 phase power? In my mind it makes sense lol.Lots of motors call for 480 VAC, my outlet only puts out 120v / 240v. Does the VFD boost up the voltage too?What's a "3rd leg" / "third leg of power"? Are those just other ways to say three phase power?

author: Berni
author_rank: Super Contributor
timestamp: November 05, 2020, 01:04:36 pm
content: A rotary converter is simply using a motor of one type to spin a generator of a different type to create a different kind of power.These used to be used a lot in the old days before power electronics became practical. They even used them for DC power supplies to turn say 3 phase AC power into 10V DC power at many kilowatts.The trick is that in some cases the motor itself can be used as a generator simultaneously, as is the case for single phase to threephase conversion. 1 of the 3 windings is used to spin the motor while the other 2 windings act as generators to create the other two missing phases. This is because you can run a 3 phase motor on single phase by first spinning it up by hand and then applying power while its spinning. The performance is of course much reduced but it works.

author: Renate
author_rank: Super Contributor
timestamp: November 05, 2020, 02:28:39 pm
content: Quote from: Berni on November 05, 2020, 01:04:36 pmWell, yeah, that was the phase converter/inverter aka rotary converter I was referring to.Of course they throw a cap on it so it can start by itself.We had a machine shop that ran off single phase converted to three phase.You'd start the converter, then start a shop tool.You could even turn off the converter at that point.After that you could even start another shop tool because the first tool is being a converter all by itself.(Of course the torque is not the same.)I had an electric lawnmower that the capacitor died.You'd turn the mower on its side, kick the blade, then switch the power on.No, this is not recommended by the Safety Institute.