GB2175761A

GB2175761A - Escalator speed control

Info

Publication number: GB2175761A
Application number: GB08612845A
Authority: GB
Inventors: Dietrich E Herrmann
Original assignee: Otis Elevator Co
Current assignee: Otis Elevator Co
Priority date: 1985-05-28
Filing date: 1986-05-27
Publication date: 1986-12-03
Also published as: DE3617621A1; JPS6231689A; AU589964B2; AU5742686A; FR2584058A1; GB8612845D0; CA1313244C; GB2175761B; DE3617621C2; FR2584058B1

Abstract

Reduced running speeds are provided for servicing an escalator by interposing a service unit 10 which is essentially a variable-frequency, variable-voltage AC-DC-AC converter, between the AC source 14 and the escalator drive motor 12. The service unit 12 comprises a rectifier 26 and inverter 28 and is adapted to be connected in the line by means of connectors 18 and 20 and plugs 22 and 24, connector 18 being of a normally-closed interrupting type whereby the line supply to the motor is broken on insertion of the plugs, and power supply to the motor is via the service unit. <IMAGE>

Description

SPECIFICATION Escalator service speed control The invention relates to driving an escalator at a reduced speed for maintenance and inspection.

It is known to drive an escalator at a reduced "service" speed for inspection and maintenance. In one arrangement, the stator of the drive motor is provided with two windings, one for normal, full speed operation and one for service speed. Such systems suffer from high starting currents, high idling currents, and unfavorable overall efficiency.

Another arrangement is to provide an auxiliary, small motor to drive the escalator at a reduced speed. This arrangement suffers from costly mechanical mounting and additional required maintenance.

Disclosure of the Ivention Therefore, it is an object of the invention to provide a simple, inexpensive means for driving escalators at reduced speed.

According to the invention, there is provided a self-contained service unit for providing reduced running speed in an elevator, comprising first connector means adapted to be connected to an a.c. supply, second connector means adapted to be connected to a motor of the elevator, and a variable frequency, variable-voltage power converter connected between said first and second connector means, at least one of said first and second connector means being adapted when so connected to the supply and motor to break an electrical connection between the supply and the motor.

In the preferred embodiment a service unit comprising a rectifier and a variable-frequency, variable-voltage inverter (in combination designated a converter), is interposed between the AC source and the motor of an escalator. The voltage and frequency outputs of the inverter are set so as to run the escalator motor at a reduced speed.

Other objects, features and advantages of the invention will become apparent in light of the following description thereof.

Brief Description of the Drawing The sole Figure contained herein is a schematic block diagram of an exemplary embodiment of the invention.

Variable-voltage, variable-frequency inverters are readily available for controlling motor speeds. An example is the LENZE TM 750series Gate Turnoff (GTO) type inverters, which are available from Lenze GmbH & Co, Aerzen 2, Hans-Lenz-Strasse 1, FRG.

The Figure shows the service unit 10 of this invention connected in the power line for an asynchronous escalator motor 12. During normal operation, an AC source 14 supplies power on a line 16 to the motor 12. (For descriptive ease, only one of the three phase power lines in shown.) Connectors 18 and 20 are fitted in the line 16. The connector 18 is of the interruptive (normally closed) type, so that when corresponding plugs 22 and 24 are inserted therein (as indicated by the dotted lines), the direct connection between the AC source and the motor is replaced by a connection through the service unit, so that all power to the motor flows through the service unit.

A rectifier 26 in the service unit first converts the AC from the source to DC, and then converts it back to AC in an inverter 28, whereupon it is provided to the motor. An inverter, such as the aforementioned LENZE 756, has a built-in controller 30, which varies the frequency and voltage of the inventer output by use of pulse-width modulation according to the setting of a set value potentiometer 32. The variable-frequency, variable-voltage output of the service unit will affect the motor speed accordingly. The combination of a rectifier and an inverter as shown in termed a converter.

For servicing an escalator, a serviceman would simply plug in the service unit, which has been preset (factory adjusted), or which can be field-adjustable, to cause the motor to run at reduced speed.

The advantages of a service unit as described above are numerous. Service speed can be adjusted to any value, from approximately 5 percent to 100 percent of rated motor speed. Low starting currents are required.

Retrofitting existing escalators simply requires installing appropriate connectors therein (and disconnecting existing service speed devices).

There are no mechanical parts involved and, perhaps the greatest advantage of all is that only one service unit is required to service numerous escalators, one at a time, or one for a single metro station, for example.

It should be understood that various modifications may be made to the invention without departing from the scope thereof.

1. A method of providing reduced running speed in a escalator having an AC drive motor, comprising: connecting an external variable-frequency, variable-voltage power converter to the drive motor; wherein the frequency and voltage of the converter are adjusted to provide the reduced running speed.

2. A method of retrofitting an escalator for reduced running speed and of providing said reduced running speed, said escalator having an AC drive motor connected via a line to an AC source, comprising: providing connectors in the line; connecting an external variable-frequency, variable-voltage power converter to the line so

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Escalator service speed control The invention relates to driving an escalator at a reduced speed for maintenance and inspection. It is known to drive an escalator at a reduced "service" speed for inspection and maintenance. In one arrangement, the stator of the drive motor is provided with two windings, one for normal, full speed operation and one for service speed. Such systems suffer from high starting currents, high idling currents, and unfavorable overall efficiency. Another arrangement is to provide an auxiliary, small motor to drive the escalator at a reduced speed. This arrangement suffers from costly mechanical mounting and additional required maintenance. Disclosure of the Ivention Therefore, it is an object of the invention to provide a simple, inexpensive means for driving escalators at reduced speed. According to the invention, there is provided a self-contained service unit for providing reduced running speed in an elevator, comprising first connector means adapted to be connected to an a.c. supply, second connector means adapted to be connected to a motor of the elevator, and a variable frequency, variable-voltage power converter connected between said first and second connector means, at least one of said first and second connector means being adapted when so connected to the supply and motor to break an electrical connection between the supply and the motor. In the preferred embodiment a service unit comprising a rectifier and a variable-frequency, variable-voltage inverter (in combination designated a converter), is interposed between the AC source and the motor of an escalator. The voltage and frequency outputs of the inverter are set so as to run the escalator motor at a reduced speed. Other objects, features and advantages of the invention will become apparent in light of the following description thereof. Brief Description of the Drawing The sole Figure contained herein is a schematic block diagram of an exemplary embodiment of the invention. Variable-voltage, variable-frequency inverters are readily available for controlling motor speeds. An example is the LENZE TM 750series Gate Turnoff (GTO) type inverters, which are available from Lenze GmbH & Co, Aerzen 2, Hans-Lenz-Strasse 1, FRG. The Figure shows the service unit 10 of this invention connected in the power line for an asynchronous escalator motor 12. During normal operation, an AC source 14 supplies power on a line 16 to the motor 12. (For descriptive ease, only one of the three phase power lines in shown.) Connectors 18 and 20 are fitted in the line 16. The connector 18 is of the interruptive (normally closed) type, so that when corresponding plugs 22 and 24 are inserted therein (as indicated by the dotted lines), the direct connection between the AC source and the motor is replaced by a connection through the service unit, so that all power to the motor flows through the service unit. A rectifier 26 in the service unit first converts the AC from the source to DC, and then converts it back to AC in an inverter 28, whereupon it is provided to the motor. An inverter, such as the aforementioned LENZE 756, has a built-in controller 30, which varies the frequency and voltage of the inventer output by use of pulse-width modulation according to the setting of a set value potentiometer 32. The variable-frequency, variable-voltage output of the service unit will affect the motor speed accordingly. The combination of a rectifier and an inverter as shown in termed a converter. For servicing an escalator, a serviceman would simply plug in the service unit, which has been preset (factory adjusted), or which can be field-adjustable, to cause the motor to run at reduced speed. The advantages of a service unit as described above are numerous. Service speed can be adjusted to any value, from approximately 5 percent to 100 percent of rated motor speed. Low starting currents are required. Retrofitting existing escalators simply requires installing appropriate connectors therein (and disconnecting existing service speed devices). There are no mechanical parts involved and, perhaps the greatest advantage of all is that only one service unit is required to service numerous escalators, one at a time, or one for a single metro station, for example. It should be understood that various modifications may be made to the invention without departing from the scope thereof. CLAIMS

2. A method of retrofitting an escalator for reduced running speed and of providing said reduced running speed, said escalator having an AC drive motor connected via a line to an AC source, comprising: providing connectors in the line; connecting an external variable-frequency, variable-voltage power converter to the line so that the drive motor is connected via the power converter to the AC source, replacing the direct connection of the drive motor via the line to the AC source; and adjusting the frequency and voltage of the converter to provide the reduced running speed.

3. A method of providing reduced running speed in an escalator, substantially as hereinbefore described with reference to the accompanying drawing.

4. A self-contained service unit for providing reduced running speed in an elevator, comprising first connector means adapted to be connected to an a.c. supply, second connector means adapted to be connected to a motor of the elevator, and a variable frequency, variable-voltage power converter connected between said first and second connector means, at least one of said first and second connector means being adapted when so connected to the supply and motor to break an electrical connection between the supply and motor.

5. A service unit as claimed in claim 3 wherein said power converter includes a rectifier and an inverter.

6. A service unit substantially as hereinbefore described with reference to the accompanying drawing.

7. An elevator system having connector means in series in a line from an a.c. source to a motor, and a service module including a variable-frequency, variable-voltage power converter, the service module being adapted to be connected to the connector means such that the series connection from the source to the motor is interrupted and the converter is connected between the source and the motor.

8. An elevator system as claimed in claim 6 wherein said power converter includes a rectifier and an inverter.

9. An elevator system substantially as hereinbefore described with reference to the accompanying drawing.