Can a 2 HP DC motor drives a 5 kW DC Generator?

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Discussion Overview

The discussion revolves around the feasibility of coupling a 2 HP DC motor to a 5 kW DC generator, exploring the implications for power output, equipment performance, and operational limits. Participants examine the relationship between motor ratings, power output, and potential risks associated with operating beyond specified limits.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that a 2 HP motor can operate a 5 kW generator but caution that it may lead to a shorter lifespan for the motor due to overheating and excessive current draw.
  • Others argue that the electrical input of the motor will always be greater than the output of the generator after accounting for efficiency losses.
  • Concerns are raised about the RPM of the motor and its importance in the context of power output and stall torque, with one participant noting that overloading the motor could lead to it stalling and drawing excessive current.
  • Some participants question the rationale behind running the motor beyond its rated capacity, suggesting it may not be a practical or safe approach.
  • A participant references a speed-torque curve for DC motors to illustrate the relationship between speed, torque, and power, indicating that there are theoretical limits to the power throughput of DC motors.

Areas of Agreement / Disagreement

Participants express differing views on the operational safety and practicality of coupling the motor and generator. While there is some consensus on the risks of overheating and reduced lifespan, there is no agreement on the overall feasibility or best practices for such a setup.

Contextual Notes

Limitations include assumptions about efficiency losses, the specific characteristics of the motor and generator, and the operational context in which they are used. The discussion does not resolve the implications of RPM on performance or the ideal operational parameters for the motor.

Who May Find This Useful

This discussion may be of interest to individuals exploring electric motor and generator interactions, those studying electrical engineering principles, or practitioners considering practical applications of DC motors and generators.

xiv_wolf
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Sorry for this noob idea but I'd like to know what happens if:

A 2 HP DC electric motor is coupled to a 5kW DC Generator, will the 5kW DC Generator produce a 5kW output? What will happen to these two equipment. Thanks for the Reply!
 
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It will work just fine under 2Hp (approx. 1.5kW). The power rating just tells you what the safe operating conditions should be. You could run a 2Hp motor at 5kW but it will have a shorter life span.

When you go past the rated power, you are drawing more current than than intended for the rated voltage. It could overheat. Also, the torque in the rotor is proportional to power being run through it so the metal has to be strong enough to handle it. If you hooked a 2Hp motor up to a 10,000Hp motor in a train, you could be sure that the big motor would just tear it to shreds.
 
In other words, the electrical input of the 2 hp motor will always be greater than (after efficiency losses) the electrical output of the 5 kW generator.
 
Okefenokee said:
It will work just fine under 2Hp (approx. 1.5kW). The power rating just tells you what the safe operating conditions should be. You could run a 2Hp motor at 5kW but it will have a shorter life span.

When you go past the rated power, you are drawing more current than than intended for the rated voltage. It could overheat. Also, the torque in the rotor is proportional to power being run through it so the metal has to be strong enough to handle it. If you hooked a 2Hp motor up to a 10,000Hp motor in a train, you could be sure that the big motor would just tear it to shreds.

Ok so there's no argument re: the power output of the Genset but on the lifespan of the motor. Is the RPM of the motor considered?
 
xiv_wolf said:
Sorry for this noob idea but I'd like to know what happens if:

A 2 HP DC electric motor is coupled to a 5kW DC Generator, will the 5kW DC Generator produce a 5kW output? What will happen to these two equipment. Thanks for the Reply!

Why would you be wanting to run the 2HP/1.5kW motor so far past its rating? You looking for a high-tech way to start a fire?
 
berkeman said:
Why would you be wanting to run the 2HP/1.5kW motor so far past its rating? You looking for a high-tech way to start a fire?

I just want to sure that energy balance is still the bottom line and driving an electric generator through an electric motor was not a good practice. Anyway, this forum helps a lot, so thank you very much!
 
xiv_wolf said:
Is the RPM of the motor considered?

Oh yeah, that's important. If you overload it to the stall torque(power) of the motor, that will stop it completely. The motor will just sit still and draw a huge current.


ETA:

I was sitting here at work and starting wondering if I gave a good answer. I really didn't.

Here is an ideal speed-torque curve for a DC motor. It shows the speed, torque, and power relationship.

torquepowerspeed.jpg


I got it from this http://lancet.mit.edu/motors/motors3.html" and added some annotations.

Note the regions that I marked. DC motors do have a theoretical limit on how much power they can throughput. The range for normal operation will end long before that.
 
Last edited by a moderator:

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