JPS61236388A - Controller of ac elevator - Google Patents

Abstract

PURPOSE:To suppress the generation of a high frequency without increasing the ripple of a DC voltage by connecting a voltage drop compensator in parallel with a smoothing condenser. CONSTITUTION:A voltage drop compensator 13 is connected in parallel with a smoothing condenser 5. The compensator 13 has a resistor 13A, a diode 13B connected in parallel with it, and a capacitor 13C connected in series with the resistor 13A. Since the charging/discharging current of the condenser 5 has large maximum value but flows through the maximum current momentarily, part of the capacity of the condenser 5 is assigned for the capacitor 13C of the compensator 13. The capacitor 13C is gradually charged through the resistor 13A to suppress a high frequency and abruptly discharges through the diode 13B at the maximum current time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a control device for an AC elevator driven by an AC motor, and in particular to one that uses an inverter to control the speed of the motor. This makes it possible to ease the restrictions on Eig Drop.

[Conventional technology]

Already, AC elevators use a converter to convert AC power from a commercial power supply into DC power, an inverter to convert this into variable voltage/variable frequency AC power, and use the converted AC power to control the speed of the car hoisting induction motor. Are known.

FIG. 3 shows a conventional AC elevator control device disclosed in, for example, Japanese Patent Application Laid-Open No. 58-154395.

In the figure, 1 indicates a commercial three-phase AC power supply, 2a, 2b, and 2c indicate the impedance of each phase, which is the sum of the impedance of the distribution line and the internal impedance of the power supply 1, 3 indicates a circuit breaker, and 4 indicates a three-phase A converter that converts alternating current to direct current. 5 is a smoothing capacitor connected in parallel to the DC output side of the converter 4; 6 is an inverter that converts the smoothed DC to AC with variable voltage and variable frequency; and 7 is a control circuit for controlling the inverter 6. 8 is inverter 6
An induction motor for car hoisting connected to the AC output side of
is a sheave connected to the electric motor 8 either directly or via a speed reduction mechanism (not shown), and a lobe 10 is wound around the sheave 9, with a cage 11 at one end and a counter at the other end. In the elevator control device configured as described above, the weights 12 are coupled to each other.
When circuit breaker 3 is closed, = phase current has impedance 2a
, 2b, 2c to the converter 41: This converter 4 rectifies the phase alternating current to convert it into direct current, and this direct current is smoothed by the action of the smoothing capacitor 5 to become a smooth direct current. Further, the smoothed DC is converted into AC with variable voltage and variable frequency by the inverter 6, and then supplied to the induction motor R8. The voltage and frequency of the alternating current are controlled with high precision by the control circuit 7, which causes the induction motor 8 to rotate and the cage 11 to move up and down.Next, considering the capacity of the smoothing capacitor 5, as is well known, Since a power loss occurs due to the dielectric loss tangent, it is necessary to have a sufficiently large capacity in order to reduce this loss and to minimize the ripple component of the DC voltage. However, as is well known, the charging current of the smoothing capacitor 5 flows only when the three-phase AC voltage is higher than the charging voltage of the smoothing capacitor 5, and since the impedances 2a, 2b, and 2c are generally small, the charging current is not supplied from the three-phase AC power supply 1. The current that flows has a pulse-like waveform rather than a sine wave.

[Problem that the invention seeks to solve]

In the conventional elevator control device configured as described above, when the capacity of the smoothing capacitor 5 is increased in order to reduce the power loss of the smoothing capacitor 5 and to reduce the voltage ripple, the peak value of the charging current increases. Moreover, since the charging current has a pulse-like waveform, it contains many high frequency components. Therefore, there is a problem in that high frequency interference is caused to other devices connected to the three-phase AC power supply.

This invention was made in order to solve the conventional problems as described above, and aims to provide a control device for an AC elevator that can suppress the generation of high frequencies without increasing the ripple component of the DC voltage. .

[Means for solving problems]

The AC elevator control device according to the present invention has a smoothing capacitor connected in parallel with a voltage drop compensation circuit including a resistor, a diode, and a capacitor.

[Effect]

In this invention, the capacitor is gradually charged, and when the elevator is operated under heavy load, the charge accumulated in the capacitor is rapidly discharged, thereby reducing ripples in the DC voltage. Suppresses the generation of high frequencies without increasing them.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a circuit diagram of a control device for an AC elevator according to the present invention. Parts that are the same as those in FIG. I will explain.

That is, the difference from FIG. 3 is that a voltage drop compensation circuit 13 is connected in parallel with the smoothing capacitor 5. This voltage drop compensation circuit 13 includes a resistor 13A, a diode 13B connected in parallel to the resistor 13A, and a capacitor 13C connected in series to the resistor 13A.

Next, the operation of this embodiment configured as above will be explained.

Figures 2 (a) to (c) show the relationship between speed, torque, and power during upward operation with the rated load loaded on the basket 11, where time 0 to t2 is an acceleration period, and time 0 to t2 is an acceleration period;
t3 is a constant speed period, t3 to t4 is a deceleration period, and the electric power reaches its maximum at time 1+ immediately before the end of acceleration.

That is, as is clear from FIG. 2(c), it is understood that the time during which the required electric power of the elevator becomes greater than that at constant speed is instantaneous. - For example, in an elevator with a rated speed of 60 m/min, the time 0-t+ is approximately 1.3 seconds,
The time t1 to t2 is approximately 0.5 seconds, and at constant speed (tz~
The power becomes larger than t3) for only about 1 second. However, the maximum value of electric power is approximately twice that at constant speed, which is quite large.

Next, the charging and discharging current of the smoothing capacitor 5 will be described.

This charging/discharging current can be considered to be approximately proportional to the required power, so the time for the current to become larger than that at constant speed is approximately 1 second, and the maximum current is approximately twice that at constant speed. it is conceivable that. Further, since the magnitude of the ripple component of the DC voltage is also proportional to the magnitude of the charging/discharging current of the smoothing capacitor 5, the same can be said.

As described above, although the maximum value of the charging/discharging current of the smoothing capacitor 5 is large, the time during which the maximum current flows is instantaneous, so a part of the capacity of the smoothing capacitor 5 is allocated to the capacitor 13C of the voltage drop compensation circuit 13. There is no problem. This capacitor 13C is gradually charged via a resistor 13A to suppress the generation of high frequency waves, and at the same time is made to be able to rapidly discharge via a diode 13B at maximum current. The charging time of the capacitor 13C may be set within about 10 seconds, which is the time taken for each floor of the elevator to run for about 5 seconds, and the door opening/closing time of about 5 seconds added thereto. Further, the value of the resistor 13A is selected to satisfy this time.

This makes it possible to suppress the generation of high frequencies without increasing the ripple component of the DC voltage even at maximum power.

Note that the operations of the converter 4 and inverter 6 are the same as those described in FIG. 3, so the explanation thereof will be omitted.

Although one embodiment of the present invention has been described above, the circuit system of the present invention can be applied in a similar manner.

That is, the impedance 28 of the three-phase AC power supply 1 and the distribution line
Because of t 2 b and 2 c, the current flowing through the distribution line at the time of the above-mentioned maximum power also reaches its maximum, and there is a possibility that the voltage at the receiving end is dropping. For this reason, the output voltage of the converter 4 decreases, and the voltage supplied to the induction motor 8 may become insufficient.

Therefore, in order to avoid the above-mentioned problems, the above-mentioned problems are generally dealt with by providing extra capacity for the power transformer or selecting thicker distribution lines, but according to the circuit system of the present invention, the above-mentioned It is possible to compensate for the voltage drop at the receiving end at maximum power even without adopting

That is, the capacitor 13 forming the voltage drop compensation circuit 13
The capacity of C is selected to be sufficiently large, and it is charged through a resistor of 13A when the elevator is stopped or when the load is light.

When the output voltage of converter 4 decreases due to distribution line impedance at maximum power, capacitor 13C
t,: By discharging the accumulated charge through the Goo 1'' 13B, the voltage drop can be compensated and the supply voltage to the induction motor 8 can be made to have no resistance. This has the effect of increasing the capacity and making the distribution line thinner.Also, when an emergency generator is used as a power source, restrictions on its internal impedance can be relaxed, and since the capacitor 13C is gradually charged, It is also possible to reduce the dissonance that occurs.

〔Effect of the invention〕

As described above, according to the present invention, since the voltage drop compensation circuit is connected in parallel with the smoothing capacitor, it is possible to suppress the generation of high frequencies without increasing the ripple component of the DC voltage. By increasing the capacitance of the capacitor that constitutes the voltage drop compensation circuit, restrictions on the impedance of power transformers and distribution lines can be relaxed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a control device for an AC elevator according to the present invention, FIGS. 2(a) to (e) are diagrams showing the relationship between speed, torque, and power in the present invention, and FIG. 3 is a diagram of a conventional AC elevator. It is a circuit diagram of a control device. DESCRIPTION OF SYMBOLS 1... Three-phase AC power supply, 3... Breaker, 4... Converter, 5... Smoothing capacitor, 6... Inverter, 8... Induction motor, 9... Sheave, 11 . . . Cart, 12 . . . Counter weight, 13 . Agent Oiwa Masuo (2 idiots) Shigeru 1 Figure 1g8-・G F > 7% -7 Kel-P agitation procedure amendment (voluntary) Showa 6th draft January 16th

Claims (1)

[Claims] AC is converted to DC by a converter, this DC is smoothed by a smoothing capacitor, and then converted to variable frequency AC by an inverter, which is connected in parallel with the smoothing capacitor in an AC elevator that drives an AC motor for car hoisting. A control device for an AC elevator, characterized in that a voltage drop compensation circuit is connected to compensate for a voltage drop and suppress the generation of high frequencies.