How can 6 HP motor be 120V?

[Russ Filtz]

Been looking for compressors and Porter Cable lists some of their 6 HP 20-25 gal. compressors for 120V @ 15 amp! The 6 is a "peak" rating, but still how is this possible? I thought for something that big you'd need 220?

[Bill Lewis]

Marketing!

It is a theoretical peak, no load, HP rating that is worthless. Same thing they do for shop vacs.

[Bill Arnold]

A 15A rating means the motor is actually 2.4HP.

120V x 15A = 1800Watts

1800W / 746(Watts per HP) = 2.4

[scott spencer]

When successfully used as a lightning rod I would guess the HP rating could go even higher .....so essentially that rating is bunk. To add to Bill's rule of thumb formula there's also losses for efficiency and power factors that reduce the HP even further from the calculation.

[Jim Becker]

A 15A rating means the motor is actually 2.4HP.

120V x 15A = 1800Watts

1800W / 746(Watts per HP) = 2.4

Less any derating for efficiency...

[Tom McDermott]

Automobiles have a similar rating system. My 1974 Ford Pinto was easily capable of achieving over 350 miles per hour! Of course, you had to lift it to 35,000 feet, point it straight down and drop it.

[Richard Gillespie]

Automobiles have a similar rating system. My 1974 Ford Pinto was easily capable of achieving over 350 miles per hour! Of course, you had to lift it to 35,000 feet, point it straight down and drop it.

You have to understand that that is theoretical. As you approach 100 mpg parts on a Ford product will come loose and start to peel off. That will act as an air brake. By the way, I don't think any other major auto manufacture would do much better.

[Ray Bersch]

How did we go from Porter Cable bashing to Ford bashing in only seven posts??

(Ok, I know, no one was Porter Cable bashing, it was just an honest question.)

[Jim Becker]

My 1974 (small automobile) was easily capable of achieving over 350 miles per hour! Of course, you had to lift it to 35,000 feet, point it straight down and drop it.

Unless you put a rocket motor in it's butt and fired it off ...thats more than 100 MPH over terminal velocity!

[Gary Max]

My luck the Pinto would run out of gas half way down.

[Richard Blaine]

Less any derating for efficiency...

And a smaller motor like that will have a 50% efficiency at best. So in reality, the motor is only giving you 1.2 hp. A far cry from the pie in the sky 6hp they are claiming.

Now who wants to talk about the inflated wattage attributed to car stereos.

[Dale Thompson]

Russ,
You are looking at a HP rating which is known as "Brake" horsepower. Correct me if I'm wrong but for "brake" HP you spin a motor at its maximum RPM, clamp it instantly to a stop and measure the torque. The torque is then coverted to HP. There is a technical validity to this but it is also used as a marketing scam. Relative amp draw is your best measure of POWER in todays competitive sales environment.

The auto industry also uses the "brake" HP thing. If you have a lot of money to lose, I'll make a bet with you. I will attach a cable from my 50 HP electric motor to your 17 Zillion HP, off-road, indestructible Hummer and see who pulls the other across the "line"! In fact, if you have three or four Hummers, I'll still give you "irresistable" odds!

Dale T.

[Michael Perata]

Russ,
I will attach a cable from my 50 HP electric motor to your 17 Zillion HP, off-road, indestructible Hummer and see who pulls the other across the "line"! In fact, if you have three or four Hummers, I'll still give you "irresistable" odds!

Dale T.

Dale

Since the thread started off talking about 120V motors, you'll be limited to 120V also, but you can use a separate circuit if you want.

[Ken Fitzgerald]

Michael.....I have a hard time imagining Dale being constrained by 120 v or anything other than what HE desires!

[Russ Filtz]

Dale, I think the analogy to BHP in autos is flawed! BHP is the real "actual" HP you should look at. I believe it's the HP the engine generates minus all the friction/mechanical losses from the crank or engine back to the wheels (hence, how much braking force the engine can overcome, or just on the edge)

Dictionary "The actual or useful horsepower of an engine, usually determined from the force exerted on a friction brake or dynamometer connected to the drive shaft."

BHP can be exaggerated, as it might only be an "instant" measure and not something you can maintain without damage (maybe similar to locked rotor amps in a motor?). "Rated" HP ratings though, should be something it should handle continuously, but then again we're dealing with marketers in the ads!