220 Electrical Question

[DennisM]

This may be a bit off the normal topic of conversation, but I could use a little help with an electrical question. For the past 10 years I have owned a Delta 14" bandsaw with the gooseneck extension. 3/4 horse motor.

As I have discovered turning, the bandsaw has seen steady use in cutting bowl blanks. Many times the saw just hasn't had enough power to slice thru a green 12" log. At times the saw has bogged down to the point that I have been forced to hit the power off switch rather quickly and then sent more time than I care to think about freeing the blade from the blank.

Sooo... today was a good day to switch the saw from 110 to 220 volt as a way to increase the power. The manual makes no mention switching from 110 to 220, but the motor clearly shows the proper color and posts numbers to switch the motor to 220. Shouldn't be a problem to make the switch at the motor.

My question is what about the switch? Do I need to make any changes at the on/off switch?
Any wisedom would be most appreciated.

 

[Mark Mandell]

Dennis,

Perhaps because they are thinking "higher voltage = more power," people think that running a motor on 220 will increase its hp. It won't. Not even a little bit. The only difference is in the amperage draw. If a 1hp motor will pull 14 amps on 110, it will only pull 7 amps on 220 but produce the same amount of driving force. What you can do with a 220 circuit that you can't do on 110 is run bigger motors on less amperage draw. If you tried to run a 3 hp table saw on a 110 you would need a 30 amp breaker and much heavier wiring or the circuit would blow.

Then there's the issue of whether your old motor is, indeed, either dual voltage or easily convertable, but that's actually irrelevant to your question.

I'm afraid that if you really want/need More Power, you're going to have to fit a larger motor or get a bigger saw.

Mark Mandell

 

[DennisM]

Are you saying that it is not worth the time involved to switch over to 220? I have the wiring already in the workshop - matter of fact on the wall right behind the bandsaw. Only expense involved is a new plug.
But will I improve my ability to cut green bowl blanks?

Thanks

 

[John Taylor]

Dennis,
The plug is only 1/2 the issue. You will have to replace the switch to one that brakes both sides of the 220V lead to the motor. The existing switch is most likely a single pole swicch for 110 V only!

The new switch would be more expensive. If you are going to go this route I would recommend a higher HP motor running on 220V and replace the push button switch with a magnetic trip 220V switch rated for the new motor.

The adventage of a magnetic trip switch is added safety. The switch is operated manually but utilizes internal electomagnet to remain energized. Any power bump or pulling the plug will cause the switch to open. The will provide added protection to the operator. The motor can't be restarted if the AC power is restored (plugging in the saw or comercial power is restored).

If you live near a big city look for an Alternator and motor shop. You can get rebuilt motors with a warrenty for a lot less than a new motor.

John Taylor

 

[DennisM]

What size HP motor is sufficient? The current 3/4 HP is OK 95% of the time, but that last 5% can be quite a bother.

 

[Dr_dewey]

What blade are you using?

Rather than replace motor - perhaps a blade with bigger gullets. You didn't mention the blade spec, for green wood i use a "furniture band" from R&D bandsaws, its 0.032", 3/8", wide kerf, big gullets and 3TPI.

the description from their site:
"Furniture Band

With a .032 blade thickness, this blade has increased beam strength, great fatigue and wear resistance. It has an extra-wide kerf designed to help cut the wet stringy fiber found in green wood. Great blade for wood turners or carver's for roughing out blanks where a smooth finish is not required. Can not be used on saws with wheels smaller than 12"."
http://www.tufftooth.com/

 

[Mark Mandell]

What size HP motor is sufficient? The current 3/4 HP is OK 95% of the time, but that last 5% can be quite a bother.

Dennis,

Since both Delta and JET have pushed their 14" saws to 1 hp motors, you should have little problem finding a motor to fit. Caution though, going too far can get you into trouble. Your saw's componants were not designed to take the stress of say the force that can be generated by say a 3hp motor; 1 to 1.5 hp would be the max I'd go in an upgrade.

On your current motor you will find information on the plate giving you the type, frame mounting, and rpm. You will have to match those specs and also check the size of the shaft to make sure the old pulley will fit on the new motor; otherwise you're looking for a new drive pulley as well.

I'll echo Dewey's comments on bands and stitches. You must replace the Delta single pole switch with a double pole switch. JET uses double pole switches on their stuff, Delta doesn't unless it's meant for 220 only. I use Timberwolf blades exclusively, but I use a 1/2" x 3 TPI AS band which is .32" thick. Great blade.

To answer your other question: Yes, just changing a plug and a switch is a complete waste of time.

Good Luck

 

[DennisM]

I want to thank everyone for their input. Seems like I had started down a wrong path. My check list now is 1) track down a rebuilt motor supplier and purchase a 1 to 1 1/2 HP rebuilt moter 2) reinstall the new motor leaving it on 110 volt 3) returning to Home Depot the 220 plug I not longer need 4) changing to a bandsaw blade that is designed to leave a wide cut.

My thanks to you all. Your assistance has been invaluable.

Dennis

 

[Mark Mandell]

Whoa . .

Dennis,

You might want to hold that plug 'till you see what the amp rating is on your replacement motor. A 1.5 hp motor can easily pull 15-18 amps, especially when cutting wet wood, and can put a fair amount of stress on a 20amp breaker on a 115v circuit. You may yet choose to go 220 for the bigger motor.

Mark

 

[DennisM]

Mark
Shall do. Thanks again

 

[JimQ]

I agree with Dr Dewey, first try a different blade. You are probably going to want one with a wider course kerf since you are not looking for a finish cut. I an using an old 1/4 HP craftsman bench model with a course blade, and have no problems with it bogging down like I did with a thin detail blade. Course it can only cut 4" thickness, but I do it all the time.

Also I would check the bearings on the wheels, if they are getting worn, they can add additional drag on the motor. Take off the blade, loosen the drive belt, and give them a spin.

JimQ

 

[Dtoggs]

220 volt ckt

What has been said is right BUTT.... If you have a dual voltage motor,a plug and a switch won't cost that much. It may or may not help depending on your existing ckt. I personally had a ckt that was not delivering enough current @110v. I changed motor interal wiring connections (it was dual voltage) and plug, and used a dedicated 220 ckt that I use for welding and planer. I have a 1hp motor. Before changing ckt,my saw would bog down when resawing. All the explanations about blade drift,sharp blade etc was tried-I just knew I needed a larger motor. I finally decided to give it a try on 220v-wa la,saw resaws great-at least compared to before. Everyone is correct about power IxE=P or more exactly Isquared R=P . What is at issue,at least in my case,was an over loaded ckt that didn't have the amperage draw. If you have the same situation,then going to 220v will indeed help,but you won't gain any power,you'll just be able to get what power your motor is capable of delivering.. I blieve if I was going to change motors,I'd go with a 1 1/2 hp and wire for 220v. This will certainly solve any electrical doubt. I think a 1 1/2 hp motor would be the max for a 14" saw,anthing more would violate Occums Razor(sp) ha ha.

 

[Bill Boehme]

Finding used motors

A good place to look for used motors is eBay. Be sure to check the seller's satisfaction rating. If it is less than 99% then look elsewhere. You will see pictures of many motors that look like they were fished up from the ocean floor and the seller will proclaim that they are "brand new with only surface rust from setting on the shelf for 10 years". Be very picky and take your time -- there are plenty of motors to choose from. I have gotten some excellent motors from perusing the listings and pouncing on a good deal when I find it.

Can someone tell me what Occums razor is? Is it related to Murphy?
Bill

 

[Mark Mandell]

Occam & His Razor

Bill,

The Razor is simplicity itself. If several scenarios present an explanation for an observed result, the simplest is most likely the correct one. See also "KISS"

Since Ol' William of Ockham was English and Murphy was, a course, a Celt, I'd rather doubt they were related.

Here's a good "short" statement on it if anyone's interested

http://skepdic.com/occam.html

Mark

 

[Clem Wixted]

Mark, your range of ...

... expertise is unfathomable!

Clem

 

[MichaelMouse]

Points to ponder.

1) 220V at half amperage will give a cooler running motor. If the thermal overload keeps popping, may be what the doctor ordered.

2) Not sure why someone would say the saw is not "strong" enough to use a motor of 1 HP or greater. The machine strength is in resisting blade tension. Motor slip and belt slip are certainly more likely than overstressing the pulley shaft. Point of thought - single belts are capable of efficient operation at ~1.5 HP, depending on size. After that, they slip under a load they should be able to pull, so you'll usually see 2 belts or a multi-rib.

3) Alternate set teeth which provide a wider kerf than the skip or hook configuration are less subject to kerf binding when cutting wet wood. Steam generation expands and binds the shreds. Though there's not a lot of friction heating, it and binding can be helped by lubricating the blade. Tradeoff is that it might slip on the tires, too.

Completely new note: blade binding due to irregular or unbalanced feed pressures on the piece. This is best served by accomodating cuts to a circle-cutting jig, so the teeth make the cut as near to the point of tangency as possible, resulting in much less twist and bind from lateral pressure on the blade. As this reduces heat, it also helps with point three. If you've ever made the comparison between freehand and jig, you know whereof I speak. It cuts sooooo much easier. If you've got the depth, use some of it for the jig.

 

[Clem Wixted]

Michael. I need help understanding...

Points to ponder.

1) 220V at half amperage will give a cooler running motor. If the thermal overload keeps popping, may be what the doctor ordered.

.

... how changing voltage will reduce heat generation. I thought P equals I x E. As the voltage goes up amperage goes down so power is constant. Do motor inefficiencies account for reduced heat on higher voltages and reduced current?

Thanks,

Clem

 

[Mark Mandell]

2) Not sure why someone would say the saw is not "strong" enough to use a motor of 1 HP or greater. The machine strength is in resisting blade tension. Motor slip and belt slip are certainly more likely than overstressing the pulley shaft. Point of thought - single belts are capable of efficient operation at ~1.5 HP, depending on size. After that, they slip under a load they should be able to pull, so you'll usually see 2 belts or a multi-rib.

Shaft bearings, brackets, springs, and castings will start to give out much faster because they were never designed for the additional stress. The belt "might" slip, but then again a stamped metal bracket may deform or a light casting may crack first, allowing the frame and blade to jump out of alignment. With a good sharp blade moving at 4,600 FPM in wet wood, you are welcome to bet on the belt. I won't. There are more reasons than the size of the motor that more powerful machines are bigger and heavier.

Met a guy who successfuly stuffed a 426 Hemi in a '62 Beetle. Asked him if he actually drove the car. Replied he was a bit nuts but not insane.

 

[MichaelMouse]

... how changing voltage will reduce heat generation. I thought P equals I x E. As the voltage goes up amperage goes down so power is constant. Do motor inefficiencies account for reduced heat on higher voltages and reduced current?

Fat wires have greater ampacity. If they're drawing less current, the wires in the windings heat less.

 

[MichaelMouse]

Met a guy who successfuly stuffed a 426 Hemi in a '62 Beetle. Asked him if he actually drove the car. Replied he was a bit nuts but not insane.

383 in a Morris Minor - "C" gas. Dragging was great until I went SCCA and learned to steer left and right....

Sorry about your mechanical apprehensions. Though, I suppose if you cranked a belt tight enough to prevent it slipping under near full torque, you'd have created a problem not with the motor rating, but with the tension side-loading the shaft. Once the shaft's rotating, mox nix. Willing to bet those bearings are rated for many times the load the bigger motor could develop short of a stall.

Of course, could be like the Leeson VS/Nova setup, where the motor shaft, because it was subject to the greatest torque and inertial resistance snapped regularly enough to cause Woodcraft to discontinue the combination.

 

[Mark Mandell]

Willing to bet those bearings are rated for many times the load the bigger motor could develop short of a stall.

At the risk of repeating myself . . .

Your Bet [when it's your saw]

 

[Mark Mandell]

Ot

383 in a Morris Minor - "C" gas. Dragging was great until I went SCCA and learned to steer left and right....

Ran my 312 '56 Sunny fairly well (in the high 9's, low 10's), but had a short ride in a '64 Fury, 426, Beefed B&M, A/FX. Quit after the left dropped out and I barely got the anchor out short of the leftside stands (never saw so many move so far so fast). Mech got banned, I got complemented. But then what did I know, I just drove the thing, and obviously God did not intend me to be a racer.

 

[Bill Boehme]

Motor temperature

MichaelMouse,

It is a very popular misunderstanding about dual voltage motors running cooler when wired for 240 volts as opposed to 120 volts, but it doesn't work that way. As far as the wires in the motor are concerned there is no difference.

Here is a very brief and simplified explanation of the way that dual voltage motors are wound and operate. The field windings (i.e., the outer fixed part of the motor -- also called the stator) of an AC induction motor consist of a number of separate windings or coils. Some of these coils are connected in series and groups of these series connected in parallel. When a motor is wound so that it can be operated on either 120 or 240 volts, leads are brought out to the junction box for two sets of coil groups. Each of these groups consists of a number of series and/or parallel coils, but I will refer to each coil group as a winding. If 120 volts is available to run the motor, then the two windings are connected in parallel so that half of the current will flow through each winding. On the other hand, if 240 volts is available to run the motor, the two windings are connected in series and thus the same total current will flow through both windings. And because the impedance of both windings is the same, the voltage across each winding will be half of the total, or 120 volts. The result is that there is no difference in power used nor efficiency of the motor. The rotor does not know the difference.

Here is a practical example:
A dual voltage motor is rated at 10 Amps for 120 volts and 5 Amps for 240 volts. When the motor is configured for 120 volts, the voltage across each set of windings is 120 volts since the windings are in parallel. Since the windings have the same impedance, the current will be divided equally between the two windings so 5 Amps will flow in each winding. When the motor is configured for 240 volts, the windings are in series so 5 Amps will flow in each winding and since the impedance of both windings are the same, the voltage across each winding will be 120 volts.

Now, the only difference in operating the motor will depend upon the wiring from the SE (service entrance) panel to the wall outlet. If it has been wired to code, there should not be any problem, but if someone had a run of 250 feet of 14 AWG wiring on a 15 Amp breaker (which, by the way is not allowed by NEC) to this motor, there would be enough voltage drop at 120 volts to cause the motor to draw more current than normal to maintain speed.

While I am on the subject of motors, I feel like I should mention that a motor does not draw its nameplate current except when it is loaded to full capacity. When a motor is running completely unloaded the current that it draws is roughly 60 to 70 percent of FLC (full load current). The unloaded current is referred to as the magnetizing current, but it also takes into account things like bearing friction; copper losses (resistance of the copper wires); iron losses (eddy currents and hysteresis in the iron laminations); and viscous drag of the bearing, cooling fan, and the air inside the motor. The motor current increases roughly proportionally to the torque load on the motor up to the maximum load. Beyond that point, the motor speed decreases rather dramatically with increased torque load and the load current increases dramatically until it reaches what is known as the locked rotor current (LRC) which is normally about 6 times the FLC. The LRC is exactly what its name implies -- the motor does not rotate and this condition should not be allowed to continue very long or else bad things will start to happen (like opening up the Grainger catalog to the motors section).

Bill Boehme

p.s. My description ignored start windings since the same thing applies to them as to the run windings or more specifically, they normally are not in the circuit long enough to do more than get the motor started.

 

[Ron Warman]

Not all motors are the same

I have to get in here. I have been made almost a laughing stock over my bandsaw " inprovements". No one will ever convince me that switching from 110 to 220 will not improve the performance of a tool. At least 3 members of our club have done it and all report an improvement in power. I know the formula, Power = amps X voltage says it should make no more power on 110 or 220 but what does make a difference is the efficiency of the motor.
The first motor I used was a capacitor run motor. I have a Delta 14" saw with the riser and I could cut a wet log 12" high if I didn't push it. I then went to a double capacitor motor, run and start. Where this motor shines is when you do push it the run capacitor kicks in and the saw dosen't slow down. The way to tell a run,start capacitor motor is it has two "humps".

I am not an engineer but I have talked this over with one and I soon learned more than I wanted to know. It takes solving a upper level math equation to explain effeciency in a motor but the bottom line is not all motors are the same. Look for the spec. service factor on the motors label. If it is over 1 it is more efficient than a motor with a rating of less than one. The most efficient motors are 3-phase but that is another story.

Ron

 

[Mark Mandell]

Ron,

No fair changing the rules of the question! Dennis only asked about changing a switch, a plug, and hooking into a 220 circuit. He wasn't bolting on additional capacitors and such, so you're not allowed to do that for your answer either.

The same motor will have the same efficiency rating regardless of the supplied current, hense without modification to the motor, simply changing the supplied voltage can not make any difference in the output power. The only way what your co-members did could have made any difference in their machines is that their changing to a dedicated 220 circuit provided more "available" current because the refrig and the shop lights weren't drawing on the same circuit as the saw any more.

It's not true that you proposed hooking up a 351 Windsor to your saw, is it?

 

[Ron Warman]

Motor upgrade?

Mark,

I feel I am on a crusade. Your statement that the same amps. will not change efficiency is just not true. If you get a chance look at a Graingers catalog. The first inch is just motors. Horsepower is one rating, efficiency is another. If your car has a HP of 150 and got 40 miles to the gallon of gas when new but ten years later the same 150 HP motor got 20 mpg wouldnt you say the motor is less efficient? All I am saying is Delta and everyone else puts a standard service motor in everything called bottom dollar supply. The guys in our group exchanged the split-phase motors Delta supplied with capacitor-start motors and went from moderate to moderate to high efficienty. Same amps. Same voltage. Just works better. Guess you would have to try it to see but it works.

Ron

 

[Mark Mandell]

Fog of War

Mark,

I feel I am on a crusade. Your statement that the same amps. will not change efficiency is just not true. If you get a chance look at a Graingers catalog. The first inch is just motors. Horsepower is one rating, efficiency is another. If your car has a HP of 150 and got 40 miles to the gallon of gas when new but ten years later the same 150 HP motor got 20 mpg wouldnt you say the motor is less efficient? All I am saying is Delta and everyone else puts a standard service motor in everything called bottom dollar supply. The guys in our group exchanged the split-phase motors Delta supplied with capacitor-start motors and went from moderate to moderate to high efficienty. Same amps. Same voltage. Just works better. Guess you would have to try it to see but it works.

Ron

Ron,

You're changing the whole motor again which was not Dennis' first question.

Let's try again. If you do nothing more than change the voltage on that "bottom dollar supply" motor that came from Delta, it will change nothing except the amount of amps the saw draws. The amount of applied voltage does not change the efficiency in a given motor. If that were true, we'd be running everything on high voltage and low amperage, and I'd have a 440 volt blender in the kitchen. Merely changing the applied voltage at the terminal block will not make the same motor more efficient, especially when, as Bill explained, the voltage across the windings remains at the very same 120v. A motor's efficiency rating is determined [far as I know] from its construction and components, not the applied current. The voltage/horsepower equation spits out a value which will, of course, vary when the amps and volts are constant but the efficiency ["Power Factor" or "Service Factor"] moves up on a higher rated motor. Obviously, if Dennis goes out and buys a higher efficiency motor, he'll get more power out of his 120v current with the same amperage draw. That's NOT what he asked or what we responded to.

No. I would say my engine/tranny are in need of a tuneup and maybe a rebuild to take care of the wear that has deprived me of 50% of my original mileage

I don't have to see if a higher efficiency motor will give better performance with the same volt/amp mix. I already know that it will.

I don't think I'm disagreeing with you. I think you're not reading carefully. No crusade necessary.

Peace

 

[Bill Boehme]

Vicmarc.fan,

Horsepower and efficiency are inextricably tied together -- they are not independent parameters. The power output (horsepower or whatever units that you want to use) of a motor is defined by the product of input power and the motor's efficiency.

I'm afraid that you are talking about two different kinds of motors and making a generalized statement as though they are the same. Just about every motor will have a different efficiency than another motor. There is a multitude of things that affect the efficiency of a motor including copper losses, iron losses, viscous drag, friction, and winding configurations. The peak efficiencies of single-phase induction motors can range from about 55% up to around 70%. The motor that you referred to with a single capacitor "bump" as a run capacitor in actuality is a start capacitor and NOT a run capacitor. The capacitor is there to shift the phase of the voltage to the start winding in order to get the motor moving and as soon as the centrifugal switch reaches the kick-out speed, the capacitor and start winding are no longer being powered. There are a few instances where a motor will be wired to leave the start winding and capacitor in the circuit, but it is not used much because it doesn't provide much improvement in efficiency. The motor with two capacitors will provide the best efficiency for a single-phase motor. One capacitor will be in series with the start winding as it accelerates up to speed and when the centrifugal switch reaches its switch point, it will switch in the second capacitor. Sometimes, they are operated in parallel and other times, the first capacitor is switched out. In either case, the capacitors are in series with the start winding which also acts like a pseudo second phase on the motor.

My description in my previous post applied to the characteristics of any given dual voltage motor and not comparing two different motors. It should have been obvious from my description that the efficiency of a dual voltage motor is not contingent upon whether it is operated on 120 or 240 volts and the manufacturers nameplate will confirm that as you will not see two different efficiency values listed (otherwise, you would also see two different horsepower values listed since horsepower is input power times efficiency)

One more thing concerning split-phase motors -- once again you are comparing two different motors which has nothing at all to do with using a dual voltage motor on 120 volts versus 240 volts. The split phase winding is a mechanism used to get the motor rotating in the right direction and one characteristic of split phase motors is that they don't have very high starting torque. The start capacitor on a motor is OUT OF THE CIRCUIT once the motor is up to speed and has nothing at all to do with the motor's performance.

Bill

 

[JimQ]

If you are going to compare apples and oranges, how about we add pomegranates?

JimQ

BTW, how is pomegranate wood for turning?

 

[DennisM]

Never would have dreamed

I never would have dreamed that my "simple" question could have started such a long running thread. I have learned a great deal, but still haven't arrived at a conclusion as to how best achieve my objective of being able to effortlessly rough out turning blanks from green 4 to 14" logs.

So I did a simple thing and call Delta. Their response was that the bandsaw can handle up to a 2 hp motor. Their parts department suggested I purchase one locally. Further they had no opinion on the capabilites of the switch.

So.... I am going to stratch the 220 idea. The 110 circuit is a 20amp circuit that I wired. I overwired the circuited my workshop when I did it, so there shouldn't be any close to capacity issues with wiring. The 220 may well cause the motor to run cooler etc., but these sound like marginal issues that don's solve my basic problem.

I will replace the motor with something in the 1 to 1 1/2 hp range that has a amp draw that the 20 amp circuit will handle. The current motor has the following info stamped on it:
11.2 /5.6 amp 115/230 volts
Continuous duty 1 Phase
Frame 56
Type SCS
KVA Code Letter J
Marathon

I understand the amp, volts, Continuous Duty, 1 phase, and Frame. I don't understand the Type SCS, KVA Code Letter J. Anybody want to weigh in with an explanation?

I have bot motors before and consisently get confused. There can be a great deal of price difference and specification difference in motors. What do I need to look for in the specs?

 

[Bill Boehme]

The only important things that you need from the old motor are the RPM and frame size (56) so that the new motor will have the same shaft size and the same mounting configuration. Otherwise, you might need to do some sheet metal work to adapt the new motor and change pulley ratios. 1.5 HP sounds like a good size -- get a replacement that is TEFC (totally enclosed fan cooled) and capacitor-start induction run to get better efficiency. You could get a capacitor-start capacitor-run motor, but you would spend a great deal more for just a little greater efficiency. Make sure that the motor has a service factor of 1.0 or better. It is up to you whether you decide to wire it for 120 or 240 volts. Available shop wiring would be your deciding factor for that decision -- don't do it because of the urban myth that somehow it will make the motor run cooler, have more power, bring good fortune, or whatever. However, it is OK to do it if it gives you a warm fuzzy when you show all your buddies that YOUR TOOLS ARE BIGGER THAN THEIR TOOLS because your tools use 240 volts.

Bill

 

[MichaelMouse]

Well, here's some motor information that should help some of the discussion.

http://www.iprocessmart.com/leeson/leeson_singlephase_article.htm

If I understand it correctly, the cooler running theoretically possible by doubling the voltage through the same gage/length of wires is squandered by placing these wires in series, effectively doubling their length.

If the same windings were used at the higher potential, less heat would be generated, but apparently they're not.

http://www.bellsouthpwp.net/a/w/awendt/HTML/InductionMotors.htm

May we assume that dual-voltage motors shipped wired 220 do not have windings in series?

 

[Bill Boehme]

There are probably various reasons that dual voltage motors are shipped prewired for 240 volts, not the least of which is advertising hype. Sometimes a dual voltage motor, especially if it is larger than 1.5 HP might be problemmatical in having an available outlet with the necessary ampacity (NEC-speak for Amperage capacity). 1.5 HP is about the largest motor that is normally shipped prewired for 120 volts. Some import motors are pretty bad when it comes to how much current they use for a given HP output and that could be another reason for prewiring the motor for 240 volts.

Bill

p.s. Those are two very good overviews of motor types. And I especially liked the Leeson information because it gives some reasons why bigger is not always better. When a motor is just loafing along not doing anything but just running unloaded, it is still using about 75% as much power as when fully loaded. If you really need the extra power, is the drive train up to it? The typical capacitor start induction run motor has a locked rotor torque of six times the full load running torque.

 

[Mark Mandell]

Thanks

Bill,

Thanks very much for jumping in with a good mix of tech and practical application and all presented well and understandably. It always best to have someone with depth of knowledge around on the subject.

Mark

 

[MichaelMouse]

Some import motors are pretty bad when it comes to how much current they use for a given HP output and that could be another reason for prewiring the motor for 240 volts.

Like my 3000, where the 14 amp 110 motor has a nameplate one horse rating? Must use tiny wires, because it warms more than my old lathe's motor even at 110.

Much more power than the old lathe at 1/2 horse, of course, but still, 14 amps?

 

[Bill Boehme]

My guess is that most of the power loss that heats up the motor and lowers efficiency is probably in the steel laminations. Motors made in the US and Europe use various specialty silicon steels that are processed to have specific grain orientations and, thus, certain B/H magnetic properties. Also the steel laminations in the stator and rotor are very thin and are well insulated from each other to reduce eddy current losses that just wastes power by heating the iron. I have disassembled some motors from the Far East and was appalled at the crummy looking construction. Who knows (probably not even the motor builders) what grade of steel(s) they use. The motor on my bandsaw looked like the laminations were at least 0.10 inch thick and rusty as all "heck" (or some other place where things rust a lot). There was no obvious insulating varnish between the "laminations".

Bill