How many watts/how much intensity needed to power an elevator?

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SUMMARY

The discussion centers on calculating the power requirements for an elevator with a mass of 1400 kg, ascending 30 meters at a speed of 4 m/s. The potential energy required for this ascent is calculated using the formula PE = mgh, resulting in approximately 411.6 kJ. The power output needed is determined to be around 54.9 kW, with a maximum current of 250 Amps when supplied with 220 volts from the power grid. The calculations utilize fundamental physics equations, including Newton's Second Law and the relationship between power, voltage, and current.

PREREQUISITES
  • Understanding of basic physics concepts, particularly potential energy (PE = mgh)
  • Familiarity with electrical power calculations (P = VI)
  • Knowledge of kinematics, specifically the equation x = vt
  • Basic understanding of Newton's Second Law (F = ma)
NEXT STEPS
  • Research the implications of power calculations in elevator design
  • Explore the efficiency of electric motors in lifting applications
  • Learn about the impact of gravitational acceleration variations on potential energy calculations
  • Investigate the safety standards and regulations for elevator electrical systems
USEFUL FOR

Engineering students, electrical engineers, and professionals involved in elevator design and maintenance will benefit from this discussion, particularly those focusing on power requirements and energy efficiency in mechanical systems.

Paulo Serrano
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Homework Statement


An elevator, with people in it, has a mass of 1400 kgs. The motor is hooked up to the power grid that provides 220 volts of power. The elevator has to go up 30 meters at 4m/s.

How many watts of potential (not sure if it's called that) are required to get the elevator moving and what is the maximum current passing through the motor?



Homework Equations


P=VI
Potential energy=mgh


The Attempt at a Solution



Not sure. I know the answer but don't know how to get to it. My idea is to calculate the change in potential energy that occurs when moving up 30m. That gets me 420kJ. That's as far as I got.

Answer: 56kW and 255A.
 
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I'm not sure this is right, but to continue what you started,

PE = mgh = 411.6 kJ

x=vt, t=x/v t=(30m)/(4m/s) = 7.5 s

P = w/t = (411.4 kJ)/(7.5s)=54.9 kW

which is kinda close to the answer. Then,

I = P/V = (54.9 kW)/(220 V)=250 Amps

which is also not quite the answer you posted, I dunno.
 
Ok I don't know how you got 420 kJ but if you use that then everything works out.
 
This question is from a national college entrance exam in Brazil. We're not allowed to use calculators, so I rounded g=9.81m/s to 10m/s.

Can you enlighten me on that formula you used to find the time? (x=vt) Just a name or wikipedia link will suffice. :)

edit: nevermind, I'm an idiot. That's the most basic formula in physics. Thanks again! :)
 
Last edited:
Newton's Second Law, F=ma.
 

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