Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1982-11-02
1985-02-19
Truhe, J. V.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
318375, 318759, B66B 128
Patent
active
044999720
DESCRIPTION:
BRIEF SUMMARY
The object of the present invention is an elevator speed control system permitting full speed of rotation of a motor with short-circuited rotor (so-called squirrel-cage motor), wherein the thyristors controlling the squirrel-cage motor permit the motor's rotation at full speed and permit, when the elevator is running in the lighter direction, operation of the motor as generated at over-synchronous speed.
It has long been known that an elevator motor may be used as generator, but in carrying out this idea there have been difficulties and it has never been introduced in practice. Therefore the old technology has persisted, according to which in the elevator's control system the actual value follows the instruction value also when running at top speed, i.e., the top speed is fixed. This results in the following drawbacks. The thermal losses are higher while running at top speed because the speed is controlled by braking the elevator when running in the lighter direction. A bigger motor is also required. The motor's highest possible speed of rotation cannot be used, owing to retention of a control margin.
The object of the present invention is to eliminate the drawbacks mentioned. The speed control system of the invention is characterized in that it comprises a controller unit assembled of components known in themselves in the art and by which the instruction value of the speed controller is increased to be considerably in excess of the actual value, whereby the squirrel-cage motor remains running at full speed, and that when commencing retardation the instruction value is dropped to be directly consistent with the actual value.
By the aid of the invention the motor of the elevator may be operated as generator at over-synchronous speed of rotation when the elevator is running in the lighter direction. The kinetic energy of the elevator is fed back into the mains and savings of electricity are achieved. No separate braking system is required for limiting the elevator's speed to its nominal speed. The thermal losses of the motor are lower than in the case that the motor speed is braked down to a given top speed.
One favourable embodiment of the invention is characterized in that the drop of the instruction value to the actual value is controllable. By the system, exceedingly simple control of deceleration is rendered possible without any change of shaft data or retardation calculator values. It should be noted that the linearity of control is not changed although the control of deceleration is performed in this way. The simplicity of this control makes possible a deceleration value as desired by the customer, an instance being hospitals, where it has to be low, and another example hotels, where it should be high in contrast.
The invention is described in the following with the aid of an example, referring to the attached drawings, wherein:
FIG. 1 presents the principle of the speed control system.
FIG. 2 presents the simplified circuit diagram of the control unit.
FIGS. 3-5 displays the speed controller's instruction and actual values, and the deceleration instruction, referred to time.
Three-phase current is supplied to the speed control system at the points A, B and C. The elevator motor is connected to D, E and F. The motor's braking circuits are connected to G and H. The control unit is EL, and its operational description is associated with FIGS. 2, 3, 4 and 5.
In the elevator's starting point situation, the start-of-retardation information SA="1" is set. The switch Q6 is conductive and Q7 is non-conductive. The output of Q2 assumes negative (-15 V) voltage. Since D57 and D53 constitute a smaller voltage selection circuit, the inverting (-) input of M9B also assumes negative (-15 V) voltage. The output of M9B is then at positive (+15 V) voltage. D62 presents its blocking direction to this voltage, whence the current flowing in resistor R124 is zero. Acceleration is started with the switch Q8, whereby AC=-15 V, and the switch Q17 changes to non-conductive state. The start rounding circuit M6B supplies the acc
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Makinen Heimo
Suur-Askola Seppo
Elevator GmbH
Ip Paul Shik Luen
Kone OY
Truhe J. V.
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