4. Given a system of five (5) 3500-lb, 700 feet per minute (fpm) elevator cars.

Question

4. Given a system of five (5) 3500-lb, 700 feet per minute (fpm) elevator cars. Gearless traction motors are being used for this system. Each car operates approximately 65% of the time and while in operation, each car draws 96% of the full load. Calculate

a. Heat generated in the machine room during peak periods. Assume solid-state control is used. (5 points)

b. Assume the following operation profile during a 24-hour day

5 hours peak use

3 hours of 70% peak

4 hours of 50% peak

12 hours of 10% peak

Calculate the approximate monthly energy cost using the electricity rate of $0.10/kWh assuming 25 days of operation per calendar month (10 points)

Explanation / Answer

Given that,

    E = 3500 x 700 = 24500000 ft lb/min = 56350 W

   Heat generated = W / V

   V = 0.96

   Heat generation = 56350 / 0.96 = 58697.9 W/m3

b) Given that,

    The working hours daily = 12 hrs

Energy consumption daily = 5365

   rate = $0.1 / Kwh

   25 days per month

Then the cost calculation = $2.02 / month

                                       = $24.68 / year.

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