JPS641392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for controlling an AC elevator.

Some elevators use an induction motor as the motor that drives the car, and operate this by connecting it to a pulse width modulation type inverter. This inverter is disclosed in, for example, Japanese Patent Laid-Open No. 123795/1983, and FIG. 1 shows an example in which this inverter is applied to an elevator.

In the figure, 1 is a three-phase AC power supply, 2a is a normally open contact of an operating electromagnetic contactor 2, which will be described later, but is closed at startup and opened after stopping, and 3 is a thyristor, which converts three-phase AC to DC. 4 is a smoothing capacitor connected to the DC side of the converter 3 to smooth the DC output;
5 is an inverter connected to both ends of the smoothing capacitor 4, and is composed of a transistor and a diode, and converts direct current into alternating current with variable voltage and variable frequency using a pulse width modulation method; 6 is connected to the alternating current side of the inverter 5. a three-phase induction motor; 7 a speed detector such as a speedometer generator that is directly connected to the motor 6 and outputs a speed signal 7a; 8 a drive sheave for a hoist driven by the motor 6; 9 a sheave 8; The main rope wrapped around the
10 and 11 are a cage and a counterweight connected to the ends of the main rope 9, respectively; 12 is a smoothing capacitor 4;
13 is a current detector that detects the output current of the inverter 5 and generates a current signal 13a; 14 is a speed command generator that generates a speed command value 14a; 15 is a speed control device whose details are shown in FIG. 2 and which emits a gate pulse signal 15a and a base drive signal 15b; 16;
17 is a phase compensation circuit that compares the speed command value 14a and the speed signal 7a and uses phase compensation to issue a slip frequency command value, and 17 is a current that inputs the slip frequency command value and calculates the current command value I shown by the following formula. Command value generation circuit, I = √ ₀ ² + ( _s ) ² where, I ₀ : Excitation current of motor 6 K : Constant determined by motor 6 ω _s : Slip frequency (phase compensation circuit 1
(Output of 6) 18 is an adder that adds the above-mentioned slip frequency command value and speed signal 7a to generate a frequency command value 18a;
9 is a voltage/frequency converter that converts the frequency command value into a pulse train, 20 is a counter that counts the pulses of the pulse train, and 21 is a read-only memory (ROM) that uses the output of the counter 20 as an address and generates a sine wave waveform. ) sine wave generation memory circuit, 22
is a digital /
An analog (D/A) converter, 23 is a pulse width modulation converter that compares the output of the D/A converter 22 and the current signal 13a and generates a pulse width modulation command value, and 24 performs inverse conversion using the pulse width modulation command value. 25 is a voltage command generation circuit that generates a voltage command value for the smoothing capacitor 4 from the frequency command value 18a; 26 is a circuit that compares the voltage command value with the voltage signal 12a; A phase compensation circuit 27 determines the firing angle of the thyristor of the converter 3, and a gate pulse signal 1 is supplied to the thyristor of the converter 3 based on the output of the phase compensation circuit 26.
5a.

That is, immediately before starting the car 10, the operating electromagnetic contactor contact 2a closes, and the electric motor 6 is connected to the converter 3,
The converted AC power is supplied via the smoothing capacitor 4 and the inverse converter 5. The electric motor 6 is now activated and the car 10 runs. Then, a gate pulse signal 15a and a base drive signal 15b are generated from the speed command value 14a, speed signal 7a, voltage signal 12a, and current signal 13a, and the converter 3 and inverse converter 5 are rotated. In this way, variable voltage/variable frequency AC power is generated from the inverter 5, and the speed of the electric motor 6, that is, the traveling speed of the car 10, is automatically controlled with high precision.

By the way, the voltage of the smoothing capacitor 4 is controlled according to the output frequency of the inverter 5 as shown in FIG. Since the speed command value and the above-mentioned output frequency while the car 10 is running are as shown in FIGS. 4a and 4b, the voltage of the smoothing capacitor 4 in this case is controlled as shown in FIG. 4c. That is, the voltage E ₀ is maintained at the start time t ₁ and the stop time t ₂ . The smoothing capacitor 4 is normally provided with a discharge resistor (not shown) for safety. Therefore, when the contact 2a opens at time _t3 as shown in FIG. 5a, the voltage across the smoothing capacitor 4 decreases as shown in FIG. 5b. Contact point 2a again at time t ₄
When the contact is closed, the smoothing capacitor 4 is rapidly charged to the voltage E ₀ before the contact is opened. At this time, a large charging current flows as shown in FIG. 5C, which may deteriorate the smoothing capacitor 4 and the thyristor of the converter 3.

In other words, in an elevator, contact 2a is activated every time the elevator stops.
It is necessary to open the smoothing capacitor 4, and during this time, the voltage of the smoothing capacitor 4 decreases due to natural discharge or the like. Since the voltage of the smoothing capacitor 4 changes depending on the time that the contact 2a is open, there is a risk that an inrush current will flow when the contact 2a closes at the next startup. In this case, it is necessary to detect the voltage of the smoothing capacitor 4 when the contact 2a is closed, and to control the output voltage of the converter 3 to a value commensurate with the voltage of the smoothing capacitor 4, which inevitably makes the circuit configuration complicated.

This invention is intended to improve the above-mentioned problem, and when the operation contact is closed at startup, the smoothing capacitor is gradually charged, and after the operation is stopped, the smoothing capacitor is discharged, and then the contact is opened, thereby simplifying the circuit. It is an object of the present invention to provide a control device for an AC elevator that is configured so that no inrush current flows when the contacts are reclosed.

An embodiment of the present invention will be described below with reference to FIGS. 6 and 7.

In the figure, 2 is an operating electromagnetic contactor, 2b is its normally open contact, 30 is a minimum value selection circuit that outputs the smaller value of input A and input B, 31 is an integrator;
1A and 31B are a DC positive power supply and a negative power supply, respectively, 31C is a resistor, 31D is an operational amplifier, and 31E
is a diode, 31F is a capacitor, 32a, 3
2b is a travel command relay contact that closes when a travel command is issued, 33 is a charge/discharge command relay, and 33a to 33
c is its normally open contact, 33d is also its normally closed contact, 3
Reference numeral 4 denotes a time relay that operates immediately when energized and returns after a certain period of time when deenergized; 34a is a normally open contact thereof, and 34b is a normally closed contact. Other than the above, the configuration is the same as in FIGS. 1 and 2.

Next, the operation of this embodiment will be explained.

Assuming that the car 10 is currently stopped, the charge/discharge command relay 33 is deenergized, so the contact 33
c is open, and the output of the integrator 31 is zero.

When a travel command is issued, the travel command relay contact 32
a, 32b are closed. The operating electromagnetic contactor 2 is energized by closing the contact 32a, and the contacts 2a and 2b
is closed. (+)-2b-32b-33-(-)
In this circuit, the charge/discharge command relay 33 is energized and self-maintained by closing the contact 33a. Further, the contacts 33b and 33c are closed, and the contact 33d is opened. The time relay 34 is energized by closing the contact 33b, and the contact 34a is closed, so that the operating electromagnetic contactor 2 is held. Further, the contact 34b is opened.
Since a negative potential is input by closing the contact 33c, the output of the integrator 31 gradually rises. While the output of the integrator 31 is lower than the voltage command value that is the output of the voltage command generation circuit 25, the minimum value selection circuit 3
0, the output of the integrator 31 is given to the phase compensation circuit 26, the converter 3 is controlled via the phase circuit 27, and the voltage of the smoothing capacitor 4 increases at a constant rate. When the output of the integrator 31 reaches the voltage command value, the minimum value selection circuit 30 selects the voltage command value, and the voltage of the smoothing capacitor 4 becomes a constant value.

Next, when a stop command is issued, travel command relay contacts 32a and 32b are opened. By opening contact 32b, charge/discharge command relay 33 is deenergized, and contact 3
3a to 33c are open, and contact 33d is closed.
By closing the contact 33d, a positive potential is input, so the output of the integrator 31 gradually decreases. When the output of the integrator 31 becomes lower than the voltage command value,
The output of the integrator 31 is given to the phase compensation circuit 26, and the voltage of the smoothing capacitor 4 is decreased at a constant rate. On the other hand, when a certain period of time has passed after the contact 33b is opened, the time relay 34 returns to its original state, and the contact 33b
4a is open and contact 34b is closed. Contact point 34
By opening a, the operating electromagnetic contactor 2 is deenergized,
Contacts 2a and 2b are opened. Integrator 31 is reset by closing contact 34b. The return timing of the time relay 34 is selected around the time when the voltage of the smoothing capacitor 4 becomes zero.

That is, when the operating electromagnetic contactor 2 is deenergized, the voltage of the smoothing capacitor 4 has decreased, so even if the contactor 2 is energized and the converter 3 is operated during the next run, the voltage of the smoothing capacitor 4 will be reduced. Inrush current as shown in Fig. 5c does not flow. Therefore, the smoothing capacitor 4 and the converter 3 will not be damaged.

Although the embodiment is constructed using an analog circuit, it can easily be constructed using a digital circuit using a microprocessor.

As explained above, in this invention, when the elevator is started, after the operation contact is closed, the smoothing capacitor is gradually charged until its voltage reaches a predetermined value, and when the elevator is stopped, after the smoothing capacitor is discharged, the contact is closed. Since the smoothing capacitor is opened, the voltage of the smoothing capacitor is zero at startup, and when the operating contact is closed, it prevents inrush current from flowing in and prevents damage to the smoothing capacitor and converter. can do. Further, since there is no need to detect the voltage of the smoothing capacitor and the converter is controlled from zero voltage, the circuit configuration can be simplified.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional AC elevator control device, Fig. 2 is a block circuit diagram showing the speed control device shown in Fig. 1, Fig. 3 is a voltage characteristic curve diagram of the smoothing capacitor shown in Fig. 4 and 5 are curve diagrams explaining the operation of FIG. 1, and FIG. 6 is a diagram showing an embodiment of the AC elevator control device according to the present invention.
The main part block circuit diagram in the figure, and FIG. 7 is a circuit diagram as well. 1...AC power supply, 2...Magnetic contactor for operation, 3
...Converter, 4...Smoothing capacitor, 5...Inverter, 6...Three-phase induction motor, 10...Elevator car, 15...Speed control device, 15a...Gate pulse signal, 30... Minimum value selection circuit, 31
. . . Integrator, 32a, 32b . . . Running command relay contact, 33 . . . Charge/discharge command relay, 34 .

Claims (1)

[Claims] 1. A converter that is connected to an AC power supply via an operating contact and converts AC into DC and whose output voltage is controlled according to an input gate pulse signal, a smoothing capacitor connected to this converter, and a smoothing capacitor connected to this converter. and an inverse converter connected to a capacitor to convert direct current to alternating current, the converted alternating current is supplied to a hoisting induction motor to operate the car, and the contact is opened after the car stops. In this case, after the contact is closed, the gate pulse signal is increased at a constant rate and then held at a constant value, and when the car stops, the gate pulse signal is decreased and the smoothing capacitor is discharged. A control device for an AC elevator, comprising a circuit that opens the contact after a sufficient period of time.