Lift And Escalator Motor Sizing.docx

LIFT AND ESCALATOR MOTOR SIZING : To calculate the size of a motor two methods can be used: 1. Steady state method 2. Dynamic method. The steady state method ensures that the motor can move the out of balance masses at the required steady state speed. The dynamic method ensures that the motor can accelerate (and possibly decelerate) the masses up to the required rated speed at the necessary rate (i.e., required acceleration). In lifts, both methods are usually used, due to the fact that one of the important performance criteria for a lift is that it is able to accelerate and decelerate in the required time. The steady state method is used to check the necessary power rating of the motor. As an additional check the dynamic method is used to ensure that the torque rating of the motor is sufficient to accelerate the motor in the necessary time. In escalators on the other hand, and due to the fact that escalators do not start and stop as frequently as lifts do, the only method usually used is the steady state method. The formula for sizing the motor for a lift is as follows: M=

P × 75 × 9.81 × s × (1−CP) η

Where: P is the rated passenger number in the car; 75 stand for 75 kg/passengers; 9.81 is the acceleration due to gravity; s is the rated top speed; CF is the counterweight factor (a factor less than 1); η is the total efficiency of the installation (taken around 85%). For a hydraulic lift, the same formula can be used by replacing CF by -1. The counterweight ratio is important, and accounts for the fact that if the counterweight ratio is less than 50%, then the worst case scenario would be for a full car moving upwards. For example, if the counterweight ratio is only 40%, then when the car is full, only 40% weight of the passengers is compensated for by the weight of the counterweight, and the motor has to provide enough torque to lift the other 60%. Using a counterweight ratio of 40% is quite common. This is in recognition of the fact that the car rarely fills up to more than 80% of its rated load.

Reference: https://www.researchgate.net/publication/276949903_Lift_and_Escalator_Motor_Sizing_with_Calculati ons_and_Examples https://platformliftco.co.uk/news-pr/traction-versus-hydraulic-lifts-advantages-and-disadvantages Fastest Elevator List: https://www.constructionweekonline.com/article-20616-burj-khalifa-has-worlds-third-fastest-elevator

PERCENTAGE OF ENERGY COSTS OF A BUILDING Motor efficiency = output mechanical power/ input electrical power Input electrical power = 3 x V x I x cos ...where V is the line voltage (usually 415 V) I is the line current and  is the phase angle. Output mechanical power (Watts) =  x n ...where n is speed in radians per second  is torque in Newton.metres 2 There are different estimates for the percentage energy dissipation of lifts as a percentage of the energy consumption of the whole building (5-15% of the total costs, depending on what other services are running in the building). KONE estimates it at 5-10%, whereas Schroeder (1987, p 189) estimates it at 15% of the total building electric energy consumption (assuming no air conditioning or oil heating). Moreover, Schroeder (1986, p189) also estimates it at 1% of the total cost of the rental of the office space.

Passenger Elevator Observation Elevator Villa Elevator Bed Elevator Freight Elevator Car Elevator