Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes control for power source of drive-means
Reexamination Certificate
2000-10-02
2002-07-23
Witkowski, Stanley J. (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes control for power source of drive-means
C187S289000, C187S393000
Reexamination Certificate
active
06422350
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a monitoring device for drive equipment for elevators. In particular, the present invention relates to a device that monitors the standstill mode of the drive after shutdown thereof.
In drive equipment for elevators with a feed and control of three-phase or direct current electric motors, the requirement to be fulfilled for the case of shutdown of the drive and monitoring of the standstill of the same is that there should be measures defined by static means. These measures are described in, for example, European Standard EN 81-1 of 1998 under 12.7. Requirements with respect to fault examination and safety devices are described in, for example, European Standard EN 81-1 of 1998 under 14.1.
An example of a monitoring device for a drive control for elevators is disclosed in European patent document EP 0 903 314 A1. This monitoring device essentially consists of a safety sensor and motor circuit and/or brake circuit and the monitoring is carried out by means of electronic components.
In particular, a monitoring device
101
with a motor-and-brake circuit
103
is connected to a drive motor
105
and a brake
106
as shown in
FIG. 3
of the EP 0 903 314 A1 document, which corresponds with
FIG. 6
of the present application. Schematically illustrated in addition is a safety circuit
104
with a signal source
110
as well as a safety sensor system
102
with a connection
120
to the motor-and-brake circuit
103
.
The motor-and-brake circuit
103
basically consists of a frequency changer power unit
150
, a VVVF drive/control unit
151
(wherein VVVF signifies variable voltage and variable frequency), an intelligent protection system
152
and a brake control
153
.
The frequency changer power unit
150
contains all electronic power components in order to transform the mains voltage into an intermediate circuit direct voltage and from that into the three-phase current for the drive motor
105
. The VVVF drive/control unit
151
is the combination of the components for drive regulation and elevator control. The VVVF drive/control unit
151
controls the frequency changer power unit
150
and is on the other hand addressed by the intelligent protection system
152
as an interface. The intelligent protection system
152
is the safety module of the electronic drive. It consists of an electronic safety circuit and monitors all functions relevant to safety.
Moreover,
FIG. 4
of the EP 0 903 314 A1 document, which corresponds to
FIG. 7
of the present application, shows a motor control. The interface between the VVVF drive/control unit
151
and the intelligent protection system
152
is very simple without electromechanical relays. The energy flow, which forms the three-phase current, to the drive motor
105
can be blocked and applied through two switching elements, namely an input direct current rectifier
155
and an IGBT alternating current rectifier
156
, by the intelligent protection system
152
via the VVVF drive/control unit
151
. The input direct current rectifier
155
is fed by three phases L
1
, L
2
, L
3
of alternating current electrical power and consists of a half thyristor bridge with a direct current rectifier control
157
. The input direct current rectifier
155
can be switched on and off by the direct current rectifier control
157
. When it is switched off, a small current flows through a charging resistor R
C
. Control signals T
1
to T
6
of a pulse width modulation PWM for drive control of the IGBT's of the alternating current rectifier
156
are checked and gated as a block by the intelligent protection system
152
via a logical linking in the VVVF drive/control unit
151
.
Measurement signals of the motor current iU, iV, and iW are prepared by the VVVF drive/control unit
151
and passed on to the intelligent protection system
152
. The monitoring function is roughly subdivided into the sequences “start”,“run” and “stop” of the drive for an elevator. The “stop” sequence follows an intermediate circuit voltage test of interest here. In that case, according to the frequency changer power unit
150
shown in
FIG. 7
an intermediate circuit capacitor C, controlled by the components TB and RB of the VVVF drive/control unit
151
, is discharged to such an extent that the intelligent protection system
152
can establish on the basis of an intermediate circuit voltage UZK whether the input direct current rectifier
155
is switched off. The drive is thereafter freed for a specific time minutes or hours) for a fresh start. If this time is exceeded, a new intermediate circuit voltage test has to be performed.
In this intermediate circuit voltage test a discharging of the capacitor C by way of TB and RB is necessary for the purpose of establishing whether the input direct current rectifier
155
is switched off. The capacitor has to be changed again later for the normal operation of the elevator. According to this state of the art circuit, an additional circuit connected downstream of the input direct current rectifier
155
is thus required by reason of the intermediate circuit lowering needed for the test.
SUMMARY OF THE INVENTION
The present invention has an object of creating a monitoring device by which it can be ascertained, without a large additional circuit, whether switching-off of the drive equipment for an elevator definitely has taken place.
In particular, according to the present invention, the ascertaining of a definite switching-off of the drive equipment is performed by a control on the input side externally of the frequency changer power unit. The input side circuit ascertains the presence or the absence of monitoring signals, which are derived from the multi-phase mains voltage, at the input of the frequency changer power unit or the static transformer. Upon ascertaining the presence of such a signal, the input side control can interrupt the energy flow to the frequency changer power unit by generating one or more switching-off signals to a switching device.
As the control device for monitoring a definite switching-off of the drive equipment is arranged at the input of the frequency changer power unit and not, as in the prior art monitoring devices, between the direct current rectifier and the alternating current rectifier, a measuring of the intermediate circuit direct voltage is superfluous. Thus, a charging and discharging of a capacitor is, according to the invention, redundant. Moreover, the device of the present invention is, due to the arrangement at the input of the frequency changer power unit, usable in a more flexible manner than the device for measuring the intermediate circuit direct voltage according to the prior art.
Further, according to the present invention preferably all three phases of the mains voltage can be individually monitored and selectively switched off. The check for an energy-free circuit can thereby be made without energy having to be applied for that purpose.
According to one embodiment, the switching device at the input of the frequency changer power unit comprises three single-phase relays with respective relay answering-back to the control at the input side.
According to a further embodiment the switching device at the input of the frequency changer power unit comprises three intrinsically safe semiconductor relays with signaling outputs for answering-back to the control at the input side.
According to another embodiment the switching device at the input of the frequency changer power unit is integrated with and the frequency changer power unit at the input is constructed as an active B
6
bridge. A sensor provided in each branch of the bridge reports the signal state in the respective bridge branch to the control at the input side. In that case, the sensor provided in each branch of the bridge is preferably a current sensor, which is, for example, a Hall sensor or a current measuring coil.
The control, to which the measured signal states are delivered, at the input side is preferably the elevator control.
REFERENCES:
patent: 4457404 (19
Inventio AG
MacMillan Sobanski & Todd LLC
Witkowski Stanley J.
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