Energy saving device for an elevator

Abstract: The invention relates to a system for the supply of energy in an elevator, in which system the elevator motor (1) is fed by a frequency converter (15) comprising a rectifier (3), an inverter bridge (2) and an intermediate circuit (4,10,11) between them. A direct voltage converter (5) is used to convert a large intermediate voltage to a level suitable for a battery (6) and the elevator's braking energy is supplied into the battery (6). The battery (6) is connected to supply power to other elevator equipment (7,8,9) except the drive motor (1).

Description: The present invention relates to a system as defined in the preamble of claim 1 for saving energy in an elevator. Such a system is known for example in document GB-A-2 139 831. In normal volume elevators, there have not been any energy saving systems so far, but the elevator's braking energy has been dissipated in a brake resistor. At present, the standard solution is to use a frequency converter drive that passes the braking energy to a resistor. This system is relatively expensive and it involves problems relating to quality and disturbances. To provide a solution to the problem and to eliminate the drawbacks mentioned, a new type of a system for saving energy in an elevator is presented as an invention. The system of the invention is characterized by what is presented in the characterization part of claim 1. Other embodiments of the invention are characterized by the features presented in the other claims. The invention allows the following advantages to be achieved: The system is cheaper and less disturbance-prone than a frequency converter that returns braking energy into the mains network Reserve power operation can be implemented without significant expenses Lighting, signalling and remote supervision can remain operative during a power failure A saving of about 20...30 % on energy is achieved in a geared elevator and about 50...60 % in a gearless one as compared to a frequency converter drive that returns braking energy into the mains network, which is currently the standard solution Eliminates the problems associated with returning energy into the mains network Improved efficiency In the following, the invention is described in detail by the aid of an example by referring to the attached drawing, in which Fig. 1 presents a simplified circuit as provided by the invention. In Fig. 1, a three-phase mains voltage is applied to a frequency converter 15 consisting of a rectifier 3, an inverter bridge 2 and an intermediate circuit 4,10,11 connected between these. When the elevator is travelling in the low-load direction, meaning that an empty car is going upwards while the counterweight is going downwards, electricity is supplied between the conductors 10,11 of the intermediate voltage circuit 4,10,11 from the drive motor 1, which is operating as a generator. The inverter bridge 2 converts the alternating voltage supplied by the drive motor 1 into a direct voltage, which is applied to the conductors 10 and 11 of the intermediate circuit 4,10,11. Using a direct voltage converter 5, a battery 6 is charged with this voltage. In the solution of the invention, only one battery 6 is needed. The power generated by the braking operation in frequency converter driven elevators (the voltage is about 650V and the current 1...3 A) is converted by means of a chopper type direct voltage converter 5 to a level of approx. 30V / 20...50A, which is well suited as a power source for an elevator and for the charging of 24V batteries. 'Chopper type converter' means a transformer implemented using semiconductors and small-size ferrite core transformers which has an efficiency comparable to that of a transformer but which provides a better degree of regulation. The same direct voltage converter 5 is used to supply power to the whole control system. The direct voltage converter 5 can be used to produce a raised voltage for the elevator's safety circuit, which consists of door contactors and other safety switches and prevents the elevator from starting when the doors are open or it is otherwise hazardous to set the elevator in motion. During approx. 20% of the travelling time, the elevator acts as an energy source, charging the battery 6 with a large current of 20...50A, and during approx. 80% of the time the energy stored in the battery 6 is used to supply power to the control equipment of the elevator, the control system, the brake and the signalling etc. Energy is supplied e.g. to the elevator control unit, identified by number 7 in the figure. This control unit needs a significant amount of electric energy. The brake 8 of the elevator refers in the first place to the braking electromagnet, which also consumes quite a deal of energy, and elevator lighting 9 refers in the first place to the car light, which generally requires a battery as a reserve power source. The capacitor 4 reduces high-frequency noise passed to the mains network. The energy generated during braking is converted to a lower voltage and supplied to elevator equipment as specified above and to the battery 6. When no braking is done, operation is almost the same as above but the power is taken from the electric network. The transmission of braking energy into the battery 6 is controlled by adjusting the voltage to a suitable level. Voltage control also ensures that the battery 6 has a sufficient voltage. Another feature of the invention is that it integrates the power sources of the elevator's drive and control systems into a single whole. So far, these have been separate from each other, which has caused additional expenses and problems relating to quality and disturbances. Using a two-way converter, reserve power operation of the elevator can be implemented so as to allow the elevator to be driven at a reduced speed for a few hours. It is obvious to the person skilled in the art that different embodiments of the invention are not restricted to the examples described above, but that they may be varied within the limits defined by the following claims.

Claims: System for the supply of energy in an elevator, in which system the elevator drive motor (1) is fed by a frequency converter (15) comprising a rectifier (3), an inverter bridge (2) and an intermediate circuit (4,10,11) between them, characterized in that a direct voltage converter (5) is used to convert a large intermediate voltage to a level suitable for a battery (6) and the elevator's braking energy is supplied into the battery (6) and the battery (6) is connected to supply power to other elevator equipment (7,8,9) except the drive motor (1). System according to claim 1, characterized in that the direct voltage converter (5) is used for the supply of power to the whole control system. System according to claim 2, characterized in that the direct voltage converter (5) is used to produce a raised voltage for the safety circuit. System according to any one of the preceding claims, characterized in that the power sources for the drive and control systems are integrated into a single whole.

Inventors: JAHKONEN PEKKA, KAEHKIPURO MATTI, JAHKONEN, PEKKA, KAEHKIPURO, MATTI, KÄHKIPURO, Matti
Applicants: KONE CORP, KONE CORPORATION
Application year: 1995
Main classification: B66B11
IPC codes: B66B11, B66B1, B66B5