JPS61254086A - Controller for ac elevator - Google Patents

Abstract

PURPOSE:To reduce the size of an AC elevator by consuming a regenerative power in a motor in a range that a motor heat is allowable, and consuming the power through a regenerative resistor over the range. CONSTITUTION:A compensator 16 generates a power drive torque command when an elevator starts. When the elevator enters a decelerating step, the compensator 16 generates a brake torque command, a current value instructing circuit 32 outputs an absolute value of a current in response to the torque command, and a frequency instructing circuit 31 outputs a frequency command necessary for a motor speed. A current command composite circuit 38 combines them, outputs a command value of the output current of an inverter 7, and a PWM unit 36 controls the transistor of the inverter 7. When the regenerative power is returned and a DC side voltage becomes higher than a DC current command value 37, a transistor base drive circuit 39 conducts a transistor 6 to consume the regenerative power by a resistor 5.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an improvement in a control device for an AC elevator that controls an elevator driven by an induction motor. [Prior Art] Driving an elevator car There is a system in which an induction motor is used as the motor for driving the car, and by controlling the slip frequency of the induction motor, the torque of the motor is controlled to drive the car. This is shown in FIGS. 4 and 5.

In the diagram, (1) is the three-phase AC power supply terminal, (2) is the terminal (1)
(2) is a magnetic contactor contact that closes when starting and opens when stopped, and (8) consists of a rectifier circuit that rectifies three-phase AC voltage into DC through contact (2). Converter, (4) is a smoothing capacitor connected to the DC side of converter (8), (6) is a smoothing capacitor (4) at one end
The resistor (6) is the transistor connected to the other end of the resistor (5) and the other end of the smoothing capacitor (4) (η is the transistor and diode connected to both ends of the smoothing capacitor (4). (8) is an inverter (
The three-phase induction motor 1 (9) driven by η is the motor (
The drive sheave for the hoist is driven by the hoist (9).
), @, aR are the heels and comb joints connected to both ends of the main rope respectively, α mark is connected to the electric motor (8) and indicates the rotation speed of the electric motor (8) A speedometer generator that emits a speed signal (13a).

) is a speed command signal, (b) is an adder that outputs a deviation signal between the speed command signal) and the speed signal (13a), and (to) is connected to the adder (b) to improve the response of the speed control system. %G (a) is the transfer function, (ISa
) is the output of the compensation element (to) and the sliding frequency command signal, (b) is the sliding frequency command signal (16a) and the speed signal (13a).
), (g) is a voltage command generator that emits a voltage command signal (18a) from the output of the adder (b), and (to) is a frequency command that also emits a frequency command signal (19a). Generator 2, ■ is an inverter control device that controls the output voltage and output frequency of the IIC-based inverter (η) using a voltage command signal (18a) and a frequency command signal (19a).

In such a configuration, the compensation element (to) outputs a sliding frequency command signal (16a) corresponding to the deviation between the speed command signal 44 and the speed signal (13a), but this sliding frequency command signal (16a) is Corresponds to the torque command signal, and an adder is added to it.
By adding the speed signal (13a) by
The voltage command signal (18a) and the frequency command signal (19a) are adjusted such that the voltage/frequency relationship is approximately constant.
can be determined. Based on these command values, the control device controls the switching of the elements of the inverter (η (if the converter (8) is composed of a thyristor etc., depending on the case, the converter (8) as well), and outputs the slip frequency command signal (
The electric motor (8) is caused to generate a torque corresponding to 16a). In this way, the electric motor (8) is activated and the heel (6) runs, and its speed is automatically controlled with high precision.

FIG. 5 shows a curve (21) of torque versus rotational speed of the electric motor (8). Here, no is the synchronous speed, and the motor (
8) is the operating point when rotated. In general, in an induction machine, near the synchronous speed n0, the torque is at the sliding frequency (for example, n
(equivalent to o-nl or non-n).

[Problem that the invention seeks to solve]

However, in the case of an elevator, when the car (2) is decelerated to a stop and is run downward at a constant speed with a single load,
The electric motor (8) must generate braking force. This is shown in FIG. 2 for a case where the necessary braking torque is TII. In this case, the rotational speed n of the electric motor (8)
2 is also higher than the synchronous speed n0. In such operation, one mechanical energy is converted into electrical energy via the electric motor (8), and regenerated power is returned to the DC side via the inverter (7).

Therefore, there is a risk that the DC side voltage will rise and destroy the elements in the inverter (7). This is protected by resistance (
6) When the transistor (6) is turned on, the regenerated power is consumed by the resistor (6). In addition, there is also one in which a regenerative inverter is provided in place of the resistor (6) and the regenerated power is returned to the power source.

However, in either case, the regenerative power processing device is expensive and the multi-control device becomes large.

Japanese Patent Application Laid-open No. 59-1787 attempted to solve this drawback.
As shown in Publication No. 9 and No. 5B-56866, regenerative power is consumed inside the motor. This method is true because the regenerative power is processed inside the motor without any special equipment, so it is difficult to control. Although there are cases where the device can be made smaller and cheaper, there are also cases where the heat generated by the motor is large, leading to an increase in the size of the motor.

This invention was made to solve the above-mentioned problems, and is intended to suppress the heat generation of the motor within an allowable range, and to make a regenerative power consumption device smaller and cheaper.

[Means for solving problems]

The control device for an AC elevator according to the present invention includes a regenerative power consumption device connected to a DC power supply, and means for controlling the power running torque of the electric motor using a torque command signal according to a deviation between a speed command signal and a speed signal of the electric motor. , and a second means for controlling the braking torque by fixing the slip of the electric motor at a predetermined value using the torque command signal and controlling the frequency and magnitude of the primary voltage or primary current; The apparatus includes a switching device that uses the first means when the torque command signal is positive and switches to the second means when the torque command signal becomes negative.

[Effect]

In the AC elevator control device according to the present invention,
When a special braking torque for deceleration of an elevator is required, the regenerated power is consumed within the motor within the allowable range of motor heat generation, and the rest beyond that is consumed by the regenerative resistor, so the device can be made smaller.

〔Example〕

Examples of the present invention will be described below.

First, the principle of this invention will be described.

Figure 2 shows an electric motor (8) to briefly explain this invention.
This is a simple equivalent circuit of

The machine power P during the first regenerative operation is expressed as an absolute value with a predetermined slip value S' as s'=-s.

On the other hand, the loss PM consumed by the winding resistance r (r any-order resistance) inside the motor is:

PM = (r, +r,) engineering @11
@1111 (2) Therefore, the power PR converted to the DC side and consumed by the regenerative resistor is PR = P, -PM = (++ r, ) 1
・Fist... (3) S' Here, what is the ratio between the power consumed by the regenerative resistor, PR, and the power consumed by the motor, PM?

r□+r2, which has no relation to the magnitude of the current and is a function only of slip. The relationship with slip SK is shown in FIG. 3.

As is clear from the figure, if S=-□.

Since the amount consumed by the regenerative resistance becomes 0, Da=0.

The power consumed at one time and the power consumed by the regenerative resistor are approximately equal.0 In the region where the absolute value of slip 8 is sufficiently small, Figure 3 is far from the actual situation, but in the region where the regenerative power is large. It corresponds well with the actual situation.

In this invention, the heat generated by the motor is a sufficiently allowable loss from the viewpoint of insulation and life span, and the slip S is selected so that the remaining power is consumed by the resistor, thereby suppressing the resistance for regenerative power consumption and reducing the heat generated by the motor. It was also designed to keep it within the allowable range.

A specific embodiment of this invention is shown in FIG.

In the figure, when the torque command is positive, the switch (29a) is connected so that the inverter (η) is controlled by a conventionally known torque control device, and when the torque command is negative, a new control means is connected. A switching means for switching, ian is a frequency command circuit that determines the output frequency of the inverter (η), and ian is a frequency command circuit that determines the output frequency of the inverter (η) so that the motor is driven at a predetermined speed e' (=-s) based on the motor rotation speed. The current value command circuit that determines the absolute value of is a current command synthesis circuit that gives the current to be output from the inverter (γ) as an instantaneous value for each phase from the absolute value of the current and the frequency.

The OR phase is output as shown below: 0, = 0, 311ω. t S phase engineering, 8 = engineering z stn (ωo t+necessaryπ) T phase engineering IT = engineering z sin (0g t+47'3w)
In addition, H is a current detector that detects the current (motor current) actually output from the inverter (η) of each phase for the above command current, and H is a comparator that compares the above current command value with the actual measured value. - is an inverter (7) according to the output of this comparator.
This is a known PWM (Pulse Width Control) device that controls the transistors of the following. Furthermore, - is a preset voltage command value, 2) is a comparator, and - is a transistor base drive circuit.

In the above configuration, when the elevator is started, the output of the compensation element a6) generates a power running torque command, so in this case, the elevator is operated by a known control device. When the deceleration process begins, the braking torque command is generated from the compensation element (to), so the absolute value of the current corresponding to the torque command is output from the current value command circuit, and the required frequency is determined from the motor rotation speed. A command is output from the frequency command circuit 41. Therefore, a current command synthesis circuit synthesizes these and outputs a command value for the output current of the inverter (7) (current to be passed through the motor). This value is compared with the actual current, and the PWM device controls the inverter (7 transistors) so that a current close to the command value flows.

On the other hand, in this embodiment, although regenerated power is returned, when power is returned to the DC side, the DC side voltage increases. This DC side voltage, a predetermined DC side voltage command value, and a comparator.
When the DC side voltage is high, the transistor (6) is made conductive through the transistor base drive circuit and the regenerated power is consumed by the resistor (5).

〔Effect of the invention〕

As explained above, according to the present invention, when special braking torque for elevator deceleration is required, regenerative power is consumed within the motor within the allowable range of motor heat generation, and beyond that is consumed by the regenerative resistor. This allows the device to be made smaller.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a control device for an AC elevator according to an embodiment of the present invention, Figs. 2 and 3 are detailed explanations of the invention, and Fig. 2 is an equivalent circuit diagram of an electric motor. 3
Figure 4 is a diagram of the subbetical characteristic curve, Figure 4 is a configuration diagram of a conventional column, Figure 5
The figure is a torque characteristic curve diagram of the electric motor shown in the FA4 diagram. In the figure, (8) is a converter, (5) is a resistor, (6) is a transistor, (7) is an inverter, (8) is a motor, and 0
! 9 is the speedometer generator % (to) is the compensation element, 4 is the switching means, -) is the torque control device, 1811 is the frequency command circuit, the beak is the current value command circuit, the glance is the current command synthesis circuit, - is the pulse In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] The DC power source is connected to an inverter to convert the DC power into variable voltage and variable frequency AC power, and the converted AC power drives an induction motor to operate the car. a regenerative power consumption device connected to a power source; a first means for controlling the power running torque of the electric motor using a torque command signal according to a deviation between a speed command signal and a speed signal of the electric motor; a second means for controlling the braking torque by fixing the slip at a predetermined value and controlling the frequency and magnitude of the primary voltage or primary current, and when the torque command signal is positive, the first means; 1. A control device for an AC elevator, characterized in that the control device includes a switching device that uses a switching means and switches to the second means when the torque command signal becomes negative.