Energy Utilized by Elevators

Since, by your own admission, you know nothing about designing elevators, why do you think the motors are too big?

The motors are sized for the maximum design load plus a safety factor. Some day, maybe, you will understand this.

Indeed. I hope "Guest" puts a highly visible plaque on every elevator he / she designs - so I can take the stairs instead.

And, when the load is less than the maximum load, the actual HP used is less.

I don't know how elevators are designed, but if you have some special application where you really want to minimize use, you might add a counterbalancing weight (picked to match some particular load condition).

For example, if the load is always (or usually) 6 PAX (weighing around 408Kgs), you could add a counterweight of 408Kgs (plus the weight of the elevator). But you might still need the same size motor to handle, for example, empty elevator movements.

I believe that traction elevators do use a counter weight system, properly designed for the intended use of the elevator. The ones I am familiar with do.

I don't know anything about hydraulic elevators, except that they all stink like stale hydraulic fluid.

Or you could make the elevator cab out of hollow aluminum tubing and pump helium into them to make the elevator go up and bleed it out to go back down.

Then you would only need a very small pump motor.

I'm really concerned about some of the assumptions you are using.

By your reference, you expect the passengers to be 68 kg each.

Are the passengers all children under 10 years of age?

A quick survey of the people here at work, most of the men are around the 95kg to 110kg, only the most sylph like women are anything approaching 68kg

Admittedly I'm in a western country with significant obesity rates per head of population.

I suggest that you do a survey of weights in your community, of the "adults", then extrapolate the mean weight then add 10 kg and use that as your single passenger weight.

I also would suggest that you obtain a copy of the design regulations appropriate to your country or copies from the different (western) countries that your elevator may be sold to. These regulations will tell you the minimum required standard that you must meet in your design. Elevators come under the auspices of OH&S in most countries.

Of course you could subscribe to this blog, you may learn something

http://cr4.globalspec.com/blogentry/15774/Hydraulic-Elevators-and-Oil-Leaks

If you connect 2 lift cars to the same rope so that the descending car lifts the ascending car you can save energy(kwh). The hp required will be used to lift the difference in the total weight of passengers in both cars. By this you are accomplishing 2 tasks at the same time. You don't need two independent motors/drives.

Since you don't mention speed it's impossible to comment re the power. Of course, the ropes must have a minimum tension and wrap or else they could slip!

6 persons is normally 450kg, and if the speed is 0.5-0.8m/s and acceleration needs to take about 2s or so, this would mean this selection if efficiency is 0.5 - 0.7 roughly, assuming counterbalance will be for normal load. I suppose you've also got a worm (inefficient) gearbox in the driveline, too.

My experience of floor conveyors is that they are more overdesigned generally, and your idea that the energy consumed is greater because of the motor selection or wrap tension is incomplete and not fully reasoned.

Please add more information like guide types, gearbox or gearless, and actual consumed power and peak torque for acceleration / deceleration if this is to be considered reasonably, I'm afraid you've not given enough to go on.

6 persons at 4kW sounds OK to me but this depends on the speed, of course.

Where are your test numbers? What criteria did you use to come up with your info?. What testing devices were used? Single test, multiple tests using same parameters?

Or just opened the door to the service room, read the motor plates and posted here?

Keeping in mind power units for elevators are sized for maximum loading plus around 10% extra. (Actually a bit more)

Please consult a code book for the area you live in before designing a elevator. All engineering design codes are laid out in these code books. A17.1 for USA, B44 for Canada, EN 81 for Europe and etc. All elevating devices must be designed to code and inspected in most countries around the world before they are put into use.

You have not understood basic electricity so well. What was given are the maximum rating of motors for the service, say 5.5Hp motor is capable of handling such power plus 10 to 25 % overload on the rating is usually as designed by motor manufacturer's.

But, take note however, when the motor runs, it does not mean it dissipate 5.5Hp power, it depends on its load.

I suggest you try to experiment this, by using an ammeter and a room fan, connect the ammeter on a wire line of the fan. Recalling basic Ohm's law: Power = Voltage x Amperage x 0.8 (this is the power factor) (Volt-Am =Watts, this when multiplied by 0.8)

The power of the fan is given on the fan plate with the serial no. model and voltage supply usually.

Voltage : Given(volts)

Power rating of fan : given(Watts)

Amperage : will be monitored , (Amps)

I want you to get the ammeter reading of two conditions

1) Fan blades are free willing to rotate

2) Fan blades are halted with your hands

Think...and Think

You will probably get the idea there.