Drive Concepts

Increased efficiancy and effort by modern inverters!

As the experiance shows the energy saving effect of a VVVF controlled lift is notably. Especially in lower turns compared with the conventional Leonardsatz and thyristor controlled Leonard-systems. In general lifts are running alternately with partial speeds and rated speeds. Data from tests regarding the distribution of speed under realistic operation terms point out that the average speed corresponds with almost the half of the rated speed. Therefore the VVVF-drive is economical and most suitable for lift-controllers as it consumes less energy than conventional systems.

1. Running the three-phase AC-motor with higher speed provides a better motor rating.
2. The result of upgrading the rating factor, effecting a reduction of the input voltage, is less loss in the inverter
3. The replacement of the motor-generator by astatic inverter results less losses as well

In summary will be determined that VVVF-controlling systems for high-speed lifts can achieve an energy saving of more than 40% compared to the Ward-Leonard-System (5-10% compared to Thyristor-Leonard System which was used in the earlier versions). Lifts with lower and medium speed of 105 m/min or less with conventionel primary-voltage-controller are tending to work with considerable slip, from which results a reducted efficiency factor and a higher waste of energy. The VVVF-System which always works constantly with low losses during the whole range of speeds achieves an energy saving of 50%.

Relevant reducted energy demand

As the conventional Thyristor-Leonard-System the DC-voltage operates so that it reacts approx. proportional to the speed of a lift, the phase-shift of input-current an input-voltage becomes bigger in the lower range of speed and the efficiancy factor gets lower proportional to the motor speed.

But with the VVVF-system there is no need to reduce the DC-voltage at low speeds, therefore the efficiancy factor keeps higher. Even as the efficiancy factor is equal with the the one of a Thyristor-Leonard-System, that works with rated speed, it is considerable improved in the range of low-speed: 20-30% increase of efficiancy factor as with Thyristor-Leonard-System when the lift is running with average speed. From that results a reduction of 20-30% on power-input.

Conventional lifts of low- and mediumspeed with controllers of primary voltage, using an induction motor which is directly connected to the power source by means of thyristors, are causing a falling off on the efficiancy factor at speed ranges due to phase-shifting of current, caused by the thyristor controller and the inductive load of the motor. Compare to that the VVVF-controllersystem uses a diode rectifier as converter and the output circuit is parallel switched by electrolyt condensors. Thus effects a lower phase-shifting between input-current and -voltage, which causes an efficiency factor close to "1". This results a reduction of more than 50% of  power need (compare to older typs).

The gearless drive

The modern frequency inverters are offering the chance to use three-phase AC-motors with direct drive without downstream gears. The gearless machines are used mainly used for systems with large lift travel and high speeds. The advantages are the high grade of efficiancy, the small size, the low noise emergence, and the little connected load. Not to neglect is also the little effort for maintenance. The gearless-drive presents a future oriented lift-machine which is being characterized by enegry saving, environmental impact, excellent passenger comfort, large travelling heights, and precise landing accuracy. Conditional is the use of the absolute encoder as shaft-copying-system and controlling the inverter by DCP-protocoll or the CANopen bus system of the lift controller.