MINI IDRAULICIDRAULIC, Electric WITH GEARLESS AND ELECTRIC MOTORS
In the previous article we tried to provide in short the main features of an elevator platform, also called mini-lift, quickly 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 most simplified way possible, the main differences as well as the multiple advantages and disadvantages of one compared to the other within an elevator. This information will be fundamental about the choice of your product reminding you that in a platform compared to the elevator you have substantially only reduced speeds of travel (0.15m/s max for the platform as per regulations).
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 for exclude certain types of elevators.
As mentioned above in addition to the hydraulic elevator, we also find the electric version, which in turn is divided into two types of product: with an asynchronous electric motor three-phase at one or two speeds placed inside a dedicated compartment above the platform, or with a new generation gearless engine with permanent magnets that is controlled by changing the frequency and voltage and for which due to its small footprint does not need a local machine.
In this type of elevator the cabin is moved to the floors thanks to a hydraulic telescopic stem 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 that thanks to the pressure generated pushes the stem upwards allowing the climb to the desired floor. The descent of the cabin is adjusted simply by draining the pressure into the tube through a valve that drains the oil into the tank, without taking advantage of additional electrical resources.
- the assembly of this type of elevator is quite easy because you mount almost all the mechanical parts in the lower floor, including the control unit and the piston. This allows a smaller number of installation hours than the other types and therefore a good economic savings;
- the system costs significantly less than an electric one as the elements of which it is composed are minor and produced in large series;
- plants of any size can be built as long as the ride is short;
- being a simple plant requires less cost in the routine maintenance phase.
- in case of power failure the return to the lower floor is always guaranteed and no batteries are needed as for electric ones;
- doesn't need a counterweight
- structurally it does not cause inconvenience to the building as the loads still weigh on the whole wall, but they are slightly lower.
- if used sporadically and therefore is often on standby the energy consumption is much lower than the electrical ones as it does not require frequency and voltage changer such as the inverter;
- may be noticeably noisier than the gearless electric ones with counterweight;
- it does not reach high speeds and races for obvious technical and economic reasons;
- The fact that you do not have a counterweight requires a higher current of cue than the counterweight implants. It must be said that obviously in a complete cycle the consumption is reduced as in the descent does not require the use of the engine but happens by gravity.
Traditional electric elevator
Electric elevators can be of different types. Those installed for most of the lifts are called clutch and have a local machine placed on top of the elevator itself. The electric motor allows the ascent and descent thanks to a motor and a series of ropes that support the cab at both ends and a counterweight that reduces the effort of the engine itself during the desired movement.
Initially the engines were clutch with direct traction and simple asynchronous engine to a winding in the state. This involved several inconveniences as traveling at a single speed, the acceleration and deceleration on the plane was not comfortable and the precision at the approximate plane. As this was not enough, it leads to a significant wear and tear of the mechanics of the winch and therefore to have to carry out frequent maintenance.
Subsequently the asynchronous engines were made to double winding and this allowed to have different speeds during the race thus allowing a much more comfortable and precise deceleration and acceleration.
Advantages over hydraulic:
- 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.
- the speed of movement is higher
- Thanks to the counterweight, the system is much more balanced and needs less power, resulting in a connection to the electrical grid to a smaller power band.
- you can dispose of higher traffic.
Disadvantages compared to the hydraulic:
- the cost is slightly higher as there is to be added the winch, counterweight and guides on which it flows.
- at the full cycle energy level is comparable to oleodynamic technology. Same for the comforts of driving and noise in the movements.
- The car compartment must be placed on top of the elevator compartment, which will weigh the weight of the cab and counterbalance directly on the slab where the engine is installed.
- In the event of a power failure, the descent to the floor is not possible compared to the oleodynamic solution unless you install an expensive battery pack.
Electric elevator with "gearless" engine
In recent years, a new technology of synchronous engines with permanent magnets has been used in the new rope systems, powered in alternating without the use of gearbox thanks to the use of the variable voltage system and variable frequency.
In fact, by changing the variation of the latter you can control both the speed of the engine itself as well as the torque. This electronic system used is called inverter.
The fact that it does not require a local machine is crucial for the widespread use of gearless engines because its small footprint is directly installed in the elevator compartment.
- it does not require a machine as the engine is installed directly in the elevator compartment, thus reducing structural inconveniences as well as unsightly. 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 moment by moment making the elevator much more efficient and reducing energy consumption
- defamed precision and leveling are much higher and stable over time
- the comfort of driving is remarkable compared to the common electrical and plumbing systems thanks to gradual accelerations and decelerations
- The speed of travel is higher and allows to dispose of much higher traffic than traditional systems
- there are fewer energy losses as no reducers are used
- the hoist wear is lower than the traditional ones as it undergoes less stress during departure and stop
- you can reach any height
- low noise
- The system has consumption even when it is standing on standby due to the presence of the inverter
- its installation is much more difficult and needs highly specialized personnel for its dangerousness: the engine must be installed at the top of the compartment with difficulty in maneuvering
- The most complex and potentially dangerous technology can lead to higher maintenance costs
- the system of returning to the floor in case of lack of electricity is very expensive as you have to buy batteries
- The frequency and voltage change system could bring electromagnetic disturbances to both the network and the station's radio sets. For this it requires special wiring special filters.
- the pulley is attached directly to the engine and in case of wear of the gorges you have to change the engine itself
- since there is no compartment the maintenance must be done by passing inside the cabin by opening the roof after taking the elevator to the highest position to be able to access the engine and its framework.
- the fact that it is a recent technology you do not have a statistic about its operation in the long run.
- The emergency manoeuvre is much more dangerous and must be done by a trained and prepared staff than an oil and dynamic system that is feasible by anyone.
As mentioned above the elevators do not have such different characteristics than the elevator platforms. If for the oil and gearless technology the characteristics are virtually the same, except for the reduced speed of the latter, the traditional electromechanical version normally also has a motor that can be placed inside the compartment at the top.
The electromechanical platform is cheaper than the others, especially if you were to change some of its parts for wear and ordinary handling itself. It turns out to be a bit noisier than the gearless version as there is a greater use of mechanical parts. Its footprint is quite comparable to the gearless version as it does not need the local machine.
In conclusion, for the reduced costs, we recommend the use of a mini-hydraulic elevator in familiar environments where use is sporadic. In environments such as shops, hospitals or airports where there are a significant number of staff to be moved the electric version is much better performing. Obviously when you have a compartment that exceeds 10 stops the elevator becomes necessary to reduce the running time.