INGENIEUR
INGENIEUR
Figure 2 : The regenerative drive system .
in both up and down directions . When the elevator car is loaded at less or more than 50 % capacity ( travelling up cars are light , or travelling down cars are heavy ) the elevator applies brakes to maintain their rated speed . Braking is provided by allowing the AC motor to operate as a generator , converting mechanical energy to electrical energy which is dissipated as heat by special heat resistors . The regenerative drive captures that energy and channels it back to the building or the city power grid [ 15 , 16 ].
The regenerative drive can harness and save energy in multiple ways including ( Figure 2 ):
● When the elevator slows down , it applies brakes and energy is created . In a conventional elevator system , that energy is dissipated as heat through a heat resister . The regenerative drive harnesses that energy .
● Whenever an empty or lightly loaded elevator goes up , the elevator applies brakes to maintain the rated speed . As in the case of slowing down , that energy is usually lost but the regenerative drive harnesses it . Further , when an empty or lightly loaded elevator goes up , the motor spins but the elevator ’ s counterweight does most of the work . The regenerative drive harnesses that spinning energy by transforming mechanical power into electrical power .
● When a heavily-loaded elevator goes down , it applies brakes to maintain the desired speed . In a conventional system , the energy created by the braking system is lost . The regenerative drive harnesses that energy . Further , when a heavily-loaded elevator goes down , the motor spins but gravity does most of the work . The regenerative drive again harnesses that spinning energy by transforming the mechanical power into electrical power .
● There are additional energy savings that result from eliminating the need to cool equipment that gets exposed to excess heat generated by conventional motors .
● By design , regenerative drives use less energy than non-regenerative drives because they are much smaller , more compact , and more efficient .
( Source : http :// www . otisworldwide . com )
Over time , these small amounts of harnessed and saved power on a daily basis add up to significant energy savings . Generally , a regenerative drive can reduce energy consumption between 20 % and 40 %. The ultimate amount of energy savings depends on several variables including length of trips , frequency and pattern of use , and age of equipment [ 28 ]. Overall , the longer the travelled distances and the greater the number of trips
18 VOL 94 APRIL-JUNE 2023