Control of an elevator hoisting motor during under voltage conditions in the main power source

• US 5,229,558 A
• Filed: 10/31/1990
• Issued: 07/20/1993
• Est. Priority Date: 10/31/1989
• Status: Expired due to Term

• Current Assignee: KONE Elevator GmbH
• Original Assignee: KONE Elevator GmbH
• Inventors: Hakala, Harri
• Primary Examiner(s): Gaffin, Jeffrey A.
• Application Number:
  US07/607,188
• Time in Patent Office: 993 Days
• Field of Search: 187/118, 187/120, 187/119, 187/114, 318/762, 361/92
• US Class Current: 187/293
• CPC Class Codes: B66B 1/30 effective on driving gear , e.g. acting on power electronics, on inverter or rectifier controlled motor

Abstract

A method and an apparatus for the control of an elevator a.c. or d.c. hoisting motor driven by a frequency converter unit, or by a rectifier unit, supplied by a three phase power source is disclosed. The voltage of the mains power source is monitored using a voltage measuring unit. The frequency converter or rectifier is supervised by a control unit which selects a speed reference curve, best suited for a run. The controller unit allows the elevator speed to be varied continuously with the mains voltage so that the elevator always travels at the highest possible speed. When an undervoltage condition is detected in the mains power source, the rotational speed of the hoisting motor is reduced without modifying the acceleration so as to avoid an overcurrent if the rectifier or inverter switches. If, in addition, the acceleration is decreased before the maximum speed is obtained, a higher maximum speed may be obtained for a given low level of supply voltage. The solution offered by this invention enables the elevator system to work at undervoltages as low as 60%.

Claims

1. A method for the control of an elevator hoisting motor, in which an a.c. motor used as a hoisting motor is connected via a frequency converter to a three phase mains power source or a d.c. motor is connected via a rectifier to a three phase mains power source, said frequency converter or rectifier being controlled by a control unit, said method comprising the steps of:

(a) monitoring the voltage of the mains power source using a voltage measuring unit;

(b) detecting an undervoltage condition in the mains power source and, depending on the severity of the undervoltage;

(b1) reducing the maximum rotational speed of the hoisting motor to a lower lever;

(b2) reducing the acceleration of the hoisting motor, before said maximum speed is attained;

or

(b3) reducing the maximum rotational speed and acceleration of the hoisting motor.

2. A procedure as claimed in claim 1, wherein an auxiliary d.c. voltage for the driving system is obtained from the mains power source.

3. A procedure as claimed in claim 1, wherein an auxiliary d.c. voltage for the driving system is obtained by means of a stabilized d.c. power supply unit.

4. An apparatus for the control of an elevator a.c. hoisting motor implementing the procedure of claim 1, comprising a frequency converter connected to a three phase mains power source for driving said a.c. hoisting motor;

a control unit for controlling the frequency converter and a voltage measuring unit connected to the control unit for detecting the voltage of the mains power source so that, when an undervoltage condition is detected the control unit reduces the rotational speed and/or acceleration of the hoisting motor.

5. An apparatus for the control of an elevator d.c. hoisting motor implementing the procedure of claim 1, comprising a rectifier connected to a three phase mains power source for driving said d.c. hoisting motor;

a control unit for controlling the rectifier and a voltage measuring unit connected to the control unit for detecting the voltage of the mains power source so that, when an undervoltage condition is detected the control unit reduces the rotational speed and/or acceleration of the hoisting motor.

6. An apparatus as claimed in claim 4 or 5, wherein the voltage measuring unit is a voltage relay.

7. An apparatus as claimed in claims 4 or 5, further comprising a stabilized d.c. power supply unit for the stabilization of the auxiliary voltage of the driving system.

8. An apparatus as claimed in claim 7, wherein stabilized d.c. power supply unit comprises means for continuous supply of electricity.

9. A method for the control of an elevator hoisting a.c. motor supplied from a three phase mains power source via a frequency converter or of a d.c. motor supplied via a rectifier, comprising the steps of:

(a) monitoring the voltage of a mains power source using a voltage measuring means; and

informing said control unit on the status of the power source voltage;

(b) determining and selecting an optimum speed for a particular measurement and varying the hoisting motor speed continuously in accordance with the voltage of the power source so as to obtain a maximum rotational speed level of the hoisting motor;

(c) reducing said maximum rotational speed level of the hoisting motor in response to the detection of an undervoltage condition in the power source; and

(d) reducing the acceleration of the hoisting motor in response to the detection of said undervoltage condition, so that a higher maximum speed level is obtained in step (c).

10. An apparatus for the control of an elevator a.c. hoisting motor having a frequency converter unit or an elevator d.c. hoisting motor having a rectifier unit connected to a three phase mains power source for driving said hoisting motor, comprising:

a voltage measuring unit, detecting the voltage of the power source;

a speed reference unit, storing simulated speed curves for controlling the frequency converter or the rectifier; and

a control unit receiving the output of said voltage measuring unit, driving said speed reference unit to select a speed reference curve to control the frequency converter or the rectifier, so that, when an undervoltage condition is detected, the rotational speed and/or acceleration of the hoisting motor of the elevator are/is reduced.