HYDRAULIC MINI LIFT, ELECTRIC WITH GEAR MOTOR AND ELECTRIC GEARLESS
In the previous article we have tried to briefly provide the main characteristics of a lifting platform, also known as a mini-lift, briefly mentioning the two categories of traction installed, namely hydraulic and electric. In this article we would like to focus on this fundamental point and describe, in the simplest way possible, the main differences as well as the many advantages and disadvantages of one compared to the other inside an elevator. This information will be essential for choosing your product, reminding you that in a platform, compared to the lift, there are substantially only lower running speeds (0.15m / s max for the platform as per legislation).
The choice of a platform must be carefully evaluated from a technical, energy and economic point of view as well as carefully assessing the structural aspect of the environment in which it is installed because the dedicated spaces will be essential to exclude certain types of elevators.
As already mentioned above, in addition to the hydraulic lift, we also find the electric version which in turn is divided into two types of product: with one or two-speed three-phase asynchronous electric motor placed inside a dedicated compartment above the platform, or with a new generation gearless motor with permanent magnets that is controlled by changing the frequency and voltage and for which, thanks to its small size, it does not require a machine room.
In this type of lift the cabin is moved to the floors thanks to a hydraulic telescopic rod on which it is fixed and the same is moved through an electric pump, placed in a dedicated machine compartment together with a tank, on which oil flows and which thanks to the pressure generated it pushes the stem upwards allowing the climb to the desired floor. The descent of the cabin is regulated simply by releasing the pressure in the pipe through a valve that lets the oil flow into the tank, without using additional electrical resources.
- the assembly of this type of lift is quite easy because almost all the mechanical parts are mounted in the lower floor, including the control unit and piston. This allows a lower number of installation hours than the other types and therefore a good economic saving;
- the system costs much less than an electric one as the elements of which it is composed are smaller and produced in large series;
- it is possible to make systems of any capacity as long as the stroke is short;
- being an altogether simple plant, it requires less costs in the ordinary maintenance phase.
- in the event of a power failure, the return to the lower floor is always guaranteed and no batteries are needed as for the electric ones;
- does not need a counterweight
- on a structural level it does not cause inconvenience to the building as the loads still weigh on the entire wall, but are slightly lower.
- if used sporadically and therefore is often in stand-by, the energy consumption is much lower than electrical ones as it does not require a frequency and voltage variator such as the inverter;
- could be significantly noisier than gearless electric ones with counterweight;
- does not reach high strokes and speeds for obvious technical-economic reasons;
- the fact of not having a counterweight requires a higher starting current than systems with a counterweight. It must be said that obviously in a complete cycle the consumption is reduced as in the descent it does not require the use of the engine but occurs by gravity.
Traditional electric lift
Electric lifts can be of different types. Those installed for most of the systems are called friction and have a machine room placed above the lift itself. The electric motor allows the ascent and descent thanks to a gear motor and a series of ropes that support the cabin at both ends and a counterweight that reduces the effort of the motor itself during the desired movement.
Initially the motors were friction with direct drive and simple asynchronous motor with one winding in the stator. This involved several inconveniences as we traveled at a single speed, the acceleration and deceleration on the floor was not comfortable and the accuracy on the floor was approximate. As if that were not enough, this leads to considerable wear on the mechanics of the winch and therefore to having to carry out frequent maintenance interventions.
Subsequently, the asynchronous motors were made with double winding and this allowed for different speeds during the stroke, thus allowing a much more comfortable and precise deceleration and acceleration.
Advantages compared to hydraulics:
- with this technology there is the possibility of reaching many more floors as it does not have the limitation that a hydraulic piston could have in its length.
- movement speed is faster
- thanks to the counterweight, the system is much more balanced and requires less starting power with consequent connection to the electricity grid at a lower power range.
- it is possible to dispose of more traffic.
Disadvantages compared to hydraulics:
- the cost is slightly higher as there is to add the winch, the counterweight and the guides on which it slides.
- in terms of energy at a complete cycle, it is comparable to hydraulic technology. Same thing for ride comfort and noise in movements.
- the machine compartment must be placed above the lift shaft with consequent burden of the weight of the cabin and counterweights directly on the slab where the motor is installed.
- in the event of a power failure the descent to the floor is not possible with respect to the hydraulic solution unless an expensive battery pack is installed.
Electric lift with gearless motor
In recent years, a new technology of permanent magnet synchronous motors has been used in the new cableway systems, powered by AC without the use of a reducer thanks to the use of the variable voltage and variable frequency system.
In fact, by changing the variation of the latter, both the speed of the motor itself as well as the torque can be controlled. This electronic system used is called an inverter.
Crucial for the widespread use of gearless motors was the fact that it did not need a machine room as it is installed directly in the lift shaft due to its small size.
- does not require a machine room as the motor is installed directly in the lift shaft thus reducing structural as well as unsightly inconveniences. In addition, the weight of the system is discharged to the bottom of the pit.
- the use of inverter technology allows you to dose current and voltage instant by instant, making the lift much more efficient and reducing energy consumption
- the maligned accuracy and leveling are much higher and stable over time
- ride comfort is remarkable compared to common electrical and hydraulic systems thanks to gradual acceleration and deceleration
- the speed of travel is higher and allows to dispose of a much higher traffic than traditional systems
- there are less energy losses as no gearboxes are used
- the wear of the winch is lower than traditional ones as it undergoes less stress during the starting and stopping phase
- you can reach any height
- low noise
- the system has consumption even when it is stopped in stand-by due to the presence of the inverter
- its installation is much more difficult and requires highly specialized personnel due to its danger: the motor must be installed in the upper part of the compartment with difficulty in maneuvering
- more complex and potentially dangerous technology can lead to higher maintenance costs
- the system for returning to the floor in the event of a power failure is very expensive as it requires the purchase of batteries
- the frequency and voltage variation system could lead to electromagnetic disturbances both in the mains supply and in the radio and TV sets of the building. For this it requires special wiring special filters.
- the pulley is attached directly to the motor and in case of wear of the grooves the motor itself must also be changed
- As there is no machine compartment, maintenance must be done by passing inside the cabin by opening the roof after having brought the lift to the highest position to access the engine and its panel.
- the fact that it is a recent technology does not have a statistic on its functioning in the long run.
- the emergency maneuver is much more dangerous and must be done by trained and trained personnel compared to a hydraulic system which is feasible by anyone.
As already mentioned above, the elevators do not have very different characteristics compared to the lifting platforms. If for the hydraulic and gearless technology the characteristics are practically the same, if not for the reduced speed of the latter, the traditional electromechanical version usually also has a gearmotor that can be placed inside the compartment in the upper part.
The electromechanical platform turns out to be cheaper than the others, especially if some of its parts have to be changed for wear and in the ordinary maintenance itself. On the other hand, it turns out to be a bit noisier than the gearless version as there is a greater use of mechanical parts. Its size is completely comparable to the gearless version as it does not require the machine room.
In conclusion, for the reduced costs, we recommend the use of a hydraulic mini-lift in familiar environments where use is sporadic. In environments such as shops, hospitals or airports where there is an important number of personnel to move, the electric version is much more efficient. Obviously, when you have a shaft that exceeds 10 stops, the lift becomes necessary to reduce travel times.