Is 50 HP really 50 HP?

[SPYDERLK]

YES. ... They question that should always be answered is: Under what load condition are those amps drawn? We cant assume where a mfg takes it. -- Either Full Load or at the SF multiple hopefully ... but which [if either].

,,,And if we are making the measurement, how do we know the motors actual load under test? -- In 4570Man example that drill press probably uses a double reduction belt pulley system. That is a load in itself even when you arent actually cutting metal.
,,,larry

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

 

[Retiredguy2]

Forgive me if I am out of place here, but this thread has morphed into a very complex discussion about ELECTRICAL horsepower and it seems quite out of place to insert that. I have done a lot of electrical work and have a fairly decent knowledge of the subject but to modify the thread about TRACTOR horsepower into ELECTRICAL horsepower seems rude to the OP. There...I said it.

 

[LD1]

That's the way things work here on TBN. A solid 3 pages before it morphed into a more complex discussion about electric motors.

What more can be said to answer the OPs question without talking about electric? This is a good thread with lots of good info. Don't matter if it strays just a bit off topic, especially since the topic was covered and the questions were answered.

Now if someone asks a legitimate question about a tractor and starting on post 2 or 3 the topic shifts to talking about hunting and fishing.....I would understand your concern.

 

[Ron50]

I ran into one situtation that I never really understood.
I installed a 3 phase 230v sewage pump rated for continuous duty to pump flood water seepage from under a large building crawl space. Head height was 9' and total 3" pipe run of 20' with two 90 degree elbows. The problem was in the motor protection panel that would trip after about 30 minutes run time. I ended up turning the controller up to about 90% to acheive continuous run. The response from the manufacture of the pump was that I needed to increase the load, ie more lift or a flow restriction, to reduce current flow. Seems backwards?
Wire was 1 size over size to control panel and pump was always submerged for cooling.
An electrician friend had the same problem with a manure pump and installed a pipe reducer to solve the same problem. I did not want to reduce the flow seeing as I was pumping during floods.
I've never got an answer to this, but this thread seems to be heading in that direction. Any input would be appreciated.

 

[SPYDERLK]

I ran into one situtation that I never really understood.
I installed a 3 phase 230v sewage pump rated for continuous duty to pump flood water seepage from under a large building crawl space. Head height was 9' and total 3" pipe run of 20' with two 90 degree elbows. The problem was in the motor protection panel that would trip after about 30 minutes run time. I ended up turning the controller up to about 90% to acheive continuous run. The response from the manufacture of the pump was that I needed to increase the load, ie more lift or a flow restriction, to reduce current flow. Seems backwards?
Wire was 1 size over size to control panel and pump was always submerged for cooling.
An electrician friend had the same problem with a manure pump and installed a pipe reducer to solve the same problem. I did not want to reduce the flow seeing as I was pumping during floods.
I've never got an answer to this, but this thread seems to be heading in that direction. Any input would be appreciated.

When you have very low back pressure you pump so much more water that there is actually more load. Its counter intuitive until you look at whats happening. -- The pump takes water that is sitting still and crams it into a pipe. In the process the water is accelerated, a lot, very quickly. This requires force - the more water the more force. -- I would try to rig up some auxiliary cooling for the motor so you can pump max.

 

[jenkinsph]

I ran into one situtation that I never really understood.
I installed a 3 phase 230v sewage pump rated for continuous duty to pump flood water seepage from under a large building crawl space. Head height was 9' and total 3" pipe run of 20' with two 90 degree elbows. The problem was in the motor protection panel that would trip after about 30 minutes run time. I ended up turning the controller up to about 90% to acheive continuous run. The response from the manufacture of the pump was that I needed to increase the load, ie more lift or a flow restriction, to reduce current flow. Seems backwards?
Wire was 1 size over size to control panel and pump was always submerged for cooling.
An electrician friend had the same problem with a manure pump and installed a pipe reducer to solve the same problem. I did not want to reduce the flow seeing as I was pumping during floods.
I've never got an answer to this, but this thread seems to be heading in that direction. Any input would be appreciated.

While it may seem strange to add a restriction it can work. Squirrel cage blower fans require a slight restriction to operate correctly in most cases.

 

[Redneck in training]

The power required by the pump is a product of mass flow and head. Then the actual behavior of the pump depends on its "performance curve". If the curve is flat the then as you throttle flow the flow decreases faster than the head increases thus the pump requires less power. In the opposite case when the performance curve is steep trottling will increase power because as you trottle flow head increases faster than flow decreases. Here is an example of flat performance curve. Performance Curves and NPSH Tests | Pumps & Systems . Never throttle pump in suction because it will cause cavitation, always throttle pump in discharge.

 

[Texasmark]

Forgive me if I am out of place here, but this thread has morphed into a very complex discussion about ELECTRICAL horsepower and it seems quite out of place to insert that. I have done a lot of electrical work and have a fairly decent knowledge of the subject but to modify the thread about TRACTOR horsepower into ELECTRICAL horsepower seems rude to the OP. There...I said it.

The thread title was a question about 50 hp really being 50 hp. 746 volt amps is a hp. Lifting 33000# 1 ft per minute or whatever that definition is, is a hp. [100 ft lbs of torque spinning at 1000 rpm]/5252 is 19.04 hp. To get one out of that you need to divide the torque or the rpms by 19.04. I was too lazy to do that. All are different forms of hp. We just got into a discussion concerning the Volt-amp aspect.....watts at a PF of unity.

 

[sd455dan]

~ ... Sorta yes. From what I have been able to pick up and make sense of over a lifetime of experience, listening and reading, the series wound motor characteristic cant be lumped with other electric motors without a hard look.

,,,My 1st exposure came from Dad telling me that a starter motor was a series wound motor and should not be run without load because there was nothing to limit its speed and the rotor could explode.

just a little clarification

unless i am mistaken - you mean the armature or possibly the commutator, - not rotor

rotors are generally employed in alternators


Back to the thread Hp is HP but

jmo
average torque and HP over the most used rpm range gives a much better indication of an engines character.
more telling than just the peak tested hp. my :2cents:

 

[Redneck in training]

Serial motor speed without a load is limited by aerodynamic drag, cooling fan and bearing friction. It is quite possible that the rotor winding of some motors will be pulled out by centrifugal forces destroying the motor. Most serial motors can be run without a load. BTW serial motor can be operated with AC or DC.