Old electric HP ratings motors vs new ones?

Kentucky

Kentucky

Joined
Dec 13, 2008
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Anyone noticed that old electric motors seem to have more power than newer motors rated at the same HP? Or is it just me? I came into possesion of a very old Baldor 1 1/2 HP. It has two grease zerks, one on either end..I have a new farm duty 1 1/2 HP electric motor..Its a great motor but I swear that old baldor seems to be equal to at least a newer 2 hp model..Its noticably bigger than the newer motor and draws more amps as well...Is it possible that newer motors are rated differently than the older motors were?
 
Yes that does seem to be the case. I don't know what changed in the ratings but most newer motors don't put out anywhere near what they claim to.
 
Older motors often put out a bit more than they were strictly rated at. Many new motors put out somewhat less actually than they are rated at.

Comparing quality older to quality newer motors though, power-to-weight and power-to-size has improved, I'd say.
 
When I was a kid, things were made to last years. When my dad was a kid, things were made to last a lifetime. Today, things are made to last until the warranty expires...or less.

Motors used to have much heavier casings, bigger windings, and better bearings. They were rated in real numbers,too. A horsepower was a 750 watts of power.
Today they talk about "Developed HP" and often claim that motors running on 500 watts "develop" 3HP.

Even on good motors, like Baldor, the old ones do seem a bit more powerful than the new ones.
 
Is that like my 5HP air compressor running off 110VAC? Or my 3HP electric chainsaw, again running 110VAC. . .

Electric motor HP is exactly 746watts of power output. Modern, more efficient motors will require fewer amps to get 746 watts than older motors. Historically, measuring the HP has varied drastically depending on the method used. That said, manufacturers were likely more generous in the past than they are today.
 
zaph1, 5 true hp cant be pulled from a 110v outlet..Thats over 33 amps, 3730 watts of power..Way more than a standard 110v outlet was designed to handle..
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Ive done a lot of research and talking to knowledgable folks since I started this thread..Theres a motor shop less than a mile from my house..
Im not a electrician but the math is correct..You'll get no more than 1875 watts from 15 amps at 125 volts...
Even if the motors energy efficancy was 100% (which it aint) Your still only looking at an available 2.5 hp from a 15A, 125v breaker and thats if it was giving 100% without tripping which it would on the startup phase..On a 20A breaker at 125v your looking at a max of 3.3 hp at 100% motor efficancy and without the breaker tripping..
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I think that some newer motors are rated on "peak" power, not continuous. It takes "x" ammount of amps to get "x" ammount of watts to matter what you do.No motor can do otherwise.Volts*Amps=Watts, Watts/Volts=Amps
Heres a formula I found..
voltage x amps x efficancy
hp=----------------------------
746
Meaning if you have a motor that has a 70% efficancy rating, uses 125v and draws 9 maps its hp would be 1.0 hp..
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Baldor uses the formula voltage x amps x efficancy x power factor= output watts..baldor does list thier efficancy and power factor on the nameplate, or they did anyway..
heres a link I found about air compressor motor ratings...
http://www.asedeals.com/air_compressor_faq.pdf
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Most every website I found uses a loose guideline of 10 amps per HP on 115v and 5 amps per hp on 220v..
 
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Yes, I love it when I get an email asking if someone can take the motor from their 3HP shop vac and use it to run the grinder. The shop vac only cost $10 at a yard sale, and a 3HP Leeson costs several hundred dollars, plus the shop vac motor runs on 110 volts...... so they will be saving a bundle....right?

I have read some articles on how "rated" and "developed" HP are calculated...but most are just hype numbers. Amps tell the real story.
 
Kentucky got pretty technical. I thought today's horses were like some of today's kids they were lazy and it took more to get the job done.
 
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