To date, in Italy, most of the modernization of lift traction machines is conservative and consists in replacing the existing hoist/gearbox machine, typically with 2-speed motor (AC2), with a hoist/gearbox machine of new generation, sometimes with 2-speed motor (AC2) but more often with VVVF motor and inverter.
Replacing a reduction gear machine with AC2 motor with a reduction gear machine with VVVF motor with inverter is a solution which, with the same suspension system (1:1), allows the use of a smaller size machine with a lower power motor , thus limiting not only the overall dimensions but also the size of the associated inverter and above all the contractual power of the system.
In most modernisations, given the strokes and speeds of the existing system, it is possible to obtain good comfort in the car even in open loop configurations, therefore without the use of feedback (encoders), thus limiting the cost of the new solution which in any case remains an "old" and not "green" solution due to the presence of oil.
The trend of modernizations is the replacement of geared machines with gearless machines, mainly because the latter is characterized by:
- high efficiency of the permanent magnet motor which translates into reduced consumption;
- reduced dimensions which allow its transport, installation and use in any system;
- maximum comfort in the cab deriving from a more precise regulation of the gearless machine in closed loop which satisfies the specific needs of the plant;
- floor re-levelling in any load condition;
- minimum level of noise and vibrations constant over time (absence of gears/gears subject to wear);
- absence of oil and lubricants;
- reduced maintenance;
- equipped with a certified brake both against excess speed of the upward car and against uncontrolled movements of the car with doors (UCM), which means increasing the safety of the original system;
- no car speed limit;
- no travel limit.
The gearless machine is made up of a permanent magnet motor, called torque motor because it is able to supply high output torque to the shaft at low speeds, exactly as the worm gear reducer does in reduction gear machines, but without having any gear train / internal gear which is not only subject to wear but also unsuitable for high speeds as it is characterized by vibrations and noise.
The gearless machine is, in essence, an "essential" machine, made up of fewer components than the geared machine (only permanent magnet motor, traction pulley, brake and encoder) therefore with less possibility of failure and wear .
In particular, the brake that is assembled on the gearless machines is certified both against excess speed of the upward car and against uncontrolled movements of the car with doors (UCM), therefore it constitutes a safety component according to EN 81-20 :2020 as it acts directly on the clutch pulley shaft itself (which is statically supported in 2 points).
This means that the system on which the gearless machine is installed is already equipped with this "free of charge" safety component which therefore allows for an increase in the safety of the system itself, unlike what happens with geared machines for which the safety brake on the low speed shaft is an important cost option.
With gearless machines, already equipped with the high efficiency typical of permanent magnet motors, an inverter with regenerative module is increasingly used which, during operation of the machine, which acts as a generator, sends the energy yielded into the grid which can then be used to power the building's electrical loads, leading to a considerable increase in the energy efficiency of the entire elevator.
To obtain the maximum economic benefit from the use of the gearless machine it is advisable to change the suspension system from 1:1 to 2:1 as this allows the selection of a smaller size machine significantly limiting the costs of replacing the original winch .
The gearless machine, being characterized by an extremely compact design, allows easy transport and positioning in the engine room without the need for partial disassembly, as occurs with geared machines. It is also possible to position the gearless machine on existing frames with simple interfaces/adapters.
System to be upgraded:
Rated load: 480kg
Suspension 1:1
Car speed: 1m/s
Stroke: 22m
Upgraded with gearless machine and regenerative inverter.
In the case of modernization with replacement of the reduction gear machine with external support of the traction pulley (very frequent configuration in "dated" systems) with a new generation reduction gear machine, it is advisable to verify, through the system data, the best possible configuration for avoid unnecessary costly solutions.
Numerous old series of reduction gear machines were always characterized by an external support of the slow shaft, also called third support, the correct installation of which was not trivial at all. Aligning 3 supports implies extremely accurate implementations which, in the event of even minimal misalignments, could drastically reduce the life of the machine itself, or even cause dangerous damage to the shaft and bearings.
Current reduction gear machines have high static loads compared to previous series and, for this reason, the use of the third support is almost always unjustified. Furthermore, in machines with third support, hyperstatic structures, any certified brake on the slow shaft is not recognized by EN 81-20:2020 as a safety component since, despite acting on the same shaft as the clutch pulley, the latter is supported by more than 2 points.
Examples of geared to gearless upgrade
Article by Elisabetta Gasperini on ANACAM Magazine