Is 50 HP really 50 HP?

[4570Man]

I have a Baldor motor that is rated 2hp and only pulls 6.2 amps @ 230 volts. I have another motor that is rated 1.5 hp and pulls 4.2 amps @ 230 volts. Both motors are 3 phase. Maybe 3 phase is more efficient.

 

[LD1]

Any electric motor that is rated for continues duty can produce its rated hp continues, right?

That is the way it is supposed to work. Lots of air compressors, shop vacs, etc are not continuous duty. Thus the HP isnt a true figure.

Also have to look at the service factor. Most good motors are 1.15. Meaning they can make 1.15 their rated power continuous.

3 phase is more efficient, but you also got to understand that they round numbers too. They make 3HP motors and 5HP motors. No such ratings like 3.5, or 4, or 4.5. So they round.

The amps tell the story. I have seen 5HP 480v motors rated anywhere from 7 to 12 amps.
And seen 5hp 240v single phase motors rated as low as 13amps and as high as 26 or 27A.

 

[buickanddeere]

I have a Baldor motor that is rated 2hp and only pulls 6.2 amps @ 230 volts. I have another motor that is rated 1.5 hp and pulls 4.2 amps @ 230 volts. Both motors are 3 phase. Maybe 3 phase is more efficient. View attachment 449922 View attachment 449923

Three phase is carrying load current on three wires instead of two so allow a factor of the square root of three .
Three phase motors as a general rule are more efficient than a single phase motor.
I have produced 1/3HP continuous for 20 minute stints on an exercise bike. Briefly producing 2.21HP in my teens while running up stairs for physics class.

 

[mike69440]

I have a Baldor motor that is rated 2hp and only pulls 6.2 amps @ 230 volts. I have another motor that is rated 1.5 hp and pulls 4.2 amps @ 230 volts. Both motors are 3 phase. Maybe 3 phase is more efficient. View attachment 449922 View attachment 449923

Correct by square root of 3 I.e multiple by 1.73 to get single phase amps

 

[mike69440]

I have a Baldor motor that is rated 2hp and only pulls 6.2 amps @ 230 volts. I have another motor that is rated 1.5 hp and pulls 4.2 amps @ 230 volts. Both motors are 3 phase. Maybe 3 phase is more efficient. View attachment 449922 View attachment 449923

Correct by square root of 3 i.e., multiple by 1.73 to get single phase amps

 

[buickanddeere]

Correct by square root of 3 i.e., multiple by 1.73 to get single phase amps

Depends if you are multiplying or dividing if you use 1.73 or 0.707. Either works.

 

[4570Man]

I have two 1.5 hp motors which pull a tad over 14 amps at 110 volts. Pretty close to 10 amps per hp. My table saw is 3 hp and pulls 14 amps @ 220 volts, also pretty close to the 10 amps per hp. My drill press is rated at 3/4 hp and pulls 13 amps as at 110 volts. This motor was either severely underrated or highly inefficient. It is pretty powerful so I'd guess it's underrated.

 

[LD1]

I have two 1.5 hp motors which pull a tad over 14 amps at 110 volts. Pretty close to 10 amps per hp. My table saw is 3 hp and pulls 14 amps @ 220 volts, also pretty close to the 10 amps per hp. My drill press is rated at 3/4 hp and pulls 13 amps as at 110 volts. This motor was either severely underrated or highly inefficient. It is pretty powerful so I'd guess it's underrated.

When you say "it pulls xx amps".....Is that the nameplate rating? or something you are actually measuring with an amp clamp?

Because motors will "pull" alot more than they are rated for. How much more and for how long all depends on the type of the motor, SF, etc. Things like hand operated power tools, like your drill press, if you really lay on it you can overload the motor I am sure. Unless it has some other type of protection against that

 

[LD1]

I have two 1.5 hp motors which pull a tad over 14 amps at 110 volts. Pretty close to 10 amps per hp. My table saw is 3 hp and pulls 14 amps @ 220 volts, also pretty close to the 10 amps per hp. My drill press is rated at 3/4 hp and pulls 13 amps as at 110 volts. This motor was either severely underrated or highly inefficient. It is pretty powerful so I'd guess it's underrated.

When you say "it pulls xx amps".....Is that the nameplate rating? or something you are actually measuring with an amp clamp?

Because motors will "pull" alot more than they are rated for. How much more and for how long all depends on the type of the motor, SF, etc. Things like hand operated power tools, like your drill press, if you really lay on it you can overload the motor I am sure. Unless it has some other type of protection against that

 

[4570Man]

It is a name plate rating.