JPS62262679A - Controller for ac elevator - Google Patents

Abstract

PURPOSE:To prevent the torque of an induction motor from abruptly varying by suppressing the switching of a control state when the motor is brought to a regenerative operation for a short period from a power running to continue the power running so far. CONSTITUTION:A slip frequency command signal 14a output from a compensating element 14 increases as the power drive torque of an induction motor 6 increases and becomes negative when the motor 6 becomes a regenerative operation. A switching unit 18c monitors the polarity of the signal 14a to set contactors 18a, 18b on a contact (a) side when the polarity continues becoming positive or zero for a predetermined period or longer and to set them on a contact (b) side when the polarity reversely continues becoming negative. The unit 18c suppresses the switching of the contactors 18a, 18b when the fact that the signal 14a becomes negative for a short period is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an elevator driven by an induction motor.

[Prior Art] For example, a conventional elevator control device uses an induction motor as an electric motor for driving the elevator and the car, and operates the car by controlling its slip frequency in order to control its torque. It is disclosed in JP-A-59-17879. The configuration of this conventional example is shown in FIG. In the figure, (1) is a three-phase AC power supply terminal, (2) is connected to this three-phase AC power supply terminal, and (9) is connected to this three-phase AC power supply terminal.
A magnetic contactor contact that opens when the system starts up and opens when it stops;
(3) is a converter that converts the Sanwa AC power obtained through the electromagnetic contactor contact (2) into DC. A smoothing capacitor (4) is connected between the output terminals of the converter (3), and the smoothing capacitor (4) smoothes the output of the converter (3) and supplies it to the inverter (5).

The inverter (5) is a pulse width modulation inverter that converts constant DC voltage into variable voltage and variable frequency AC voltage, and this AC power drives a three-phase induction motor (hereinafter referred to as induction motor) (6). The induction motor (6) further drives a drive transverse wheel (7) of the hoist.

A main rope (8) is wound around this driving sheave (7), and a cage (9) is connected to one end of the main rope (8), and a counterweight (10) is connected to the other end.

On the other hand, (11) is a tachometer that detects the rotational speed of the induction motor (6) and outputs a speed signal (lla) representing this rotational speed. This speed signal (lla) and speed command signal (12) are added to an adder (13).

The adder (13) outputs a deviation signal obtained by subtracting the speed signal (l la) from the speed command signal (12), and outputs this to the adder (15) through the compensation element (14).

The above-mentioned compensation element (14) is for improving the response of the speed control system, and as shown in the block, the transfer function G (
s), and its output is the slip frequency command signal (
14a). This perfect frequency command signal (14a)
and the speed signal (lla) passed through the contactor (18b) are added by an adder (15). (16) is an adder (15
) input the output (15a) and output the voltage command signal (16a).
(17) is a frequency command generator that also generates a frequency command signal (17a), (17)
8) is a switching device having contacts (18a) and (18b), and when the slip frequency command signal (14a) is positive or zero, the contacts (18a) and (18b) are brought into contact with the contact a side, respectively. , slip frequency command signal (14a)
When is negative, the contacts (18a) and (18b) are brought into contact with the respective contacting sides to perform switching control. The gain converter (19) is connected to the contact point to which the contactor (18a) is switched and contacted.

When the output (15a) of the adder (15) is input, an output having a value set according to the value of this input is generated.

Further, when the contactor (18b) is switched from the illustrated position, the power control device (20) is connected to the contact point S, inputs the speed signal (lla), and generates the induction electric motor fi (6).
A frequency command signal is generated such that the regenerated power regenerated to the DC side becomes zero.

The inverter control device (21) sends a voltage command signal (16a)
.

The output voltage and output frequency of the inverter (5) are controlled based on the frequency command signal (17a), the output of the gain converter (19), and the frequency command signal of the power control device (20).

The operation of the conventional device having the above configuration will be explained.

When the induction motor (6) is running, the speed command signal (12)
The adder (1
The slip frequency command signal (14a) calculated in step 3) is positive, so the contacts (18a) and (18b) are in contact with the positions shown, that is, on the contact a side.

Therefore, the frequency command signal (14a) and the speed signal (
lla) are added by an adder (15), and the output signal (15a) is input to a voltage command generator (1G) and a frequency command generator (17).

Voltage command generator (16) and frequency command generator (17)
The voltage command signal (16a) and frequency command signal (17a) generated are controlled so as to satisfy a relationship in which the output voltage and the output frequency are substantially constant. The inverter control device (21) controls each switching element constituting the inverter (5) based on these command signals to cause the induction motor (6) to generate torque corresponding to the slip frequency command signal (14a). Controlled AC power is supplied to the induction motor (6).

By the way, when the elevator (9) is decelerated to a stop, mechanical energy is converted into electrical energy via the induction motor (6).

The regenerated power is returned to the DC side through the inverter (5). At this time, if the inverter (5) is controlled so that the above-mentioned output voltage/output frequency is approximately constant, the first regenerative energy is stored in the smoothing capacitor (4), increasing its voltage, and this capacitor (4) There is a risk of damaging itself and the inverter (5).

Therefore, during regenerative operation of the induction motor (6), switching device If (1
8) and switches the contacts (18a) (18b) to the contact side. As a result, the full frequency command signal (L4a) is input as is to the gain converter (19).

The output is used as a voltage command signal by the inverter control device i!
! (21) is added.

In addition, the power control bag hW (2, 0) is the speed signal (lla)
As input, a frequency command signal is applied to the inverter control device (21) so that the regenerated power becomes zero.

Note that control in which the first regenerative power becomes zero means that all of the mechanical energy of the rotating system, including the induction motor (6), is transferred to the induction motor (6).
) is nothing more than consuming it inside. The operating principle of the power control device (20) that generates the frequency command signal for this purpose will be explained with reference to the equivalent circuit of the induction motor shown in FIG.

Referring to FIG. 4, the electric power P□ consumed inside the induction motor (6) is P,=V2g,+r□(V/Z)2+r,(V/Z)"
...”(1) However, Z=v”(x□+x2+r□+r2/S)”
(2) Here, ■ is the AC input voltage, Z is the induction motor (6
) is the total impedance - go is the excitation conductance,
rl, r2 are -water resistance and secondary resistance (-order conversion value) of the induction motor (6), X engineering, x2 are -order leakage reactance and secondary leakage reactance (-order conversion value) of the induction motor (6) , S is the slip of the induction motor (6).

On the other hand, the electric power P2 generated as one-time regenerative electric power is.

P, = (V/Z)” ・(1-3/5)rz −
---(3) Here.

Pyu+P2=0...
...(4) If the slip S is controlled to satisfy equation (4), all mechanical energy will be consumed inside the induction motor (6).

Therefore, by substituting the above equations (1) and (3) into equation (4), a linear equation is obtained.

By finding S that satisfies equation (5) regardless of rz, the slip S that generates braking force without transmitting or receiving electric power can be found. Furthermore, if the speed signal (lla) is given, the frequency command signal to the inverter (5) is determined. Therefore, it can be seen that only the speed signal (lla) needs to be given to the power control device (20). Note that bll in FIG. 4 is an excitation susceptance.

Thus, when the induction motor (6) is running in the forward direction, the torque is controlled by the slip frequency command signal (14a) corresponding to the deviation between the speed command signal (12) and the speed signal (Ila), while during regenerative braking, the torque is controlled by the speed signal ( Protection of the smoothing capacitor (4) and the inverter (5) is achieved by controlling the frequency command signal given to the inverter (5) by ffi to make the regenerated power of the induction electric motor fi (6) zero.

[Problems to be Solved by the Invention] The conventional AC elevator control device is configured as described above, so that even if the polarity of the slip frequency command changes for a short period of time, the one selection device will follow the polarity. From the first control state to the second control state.

Or vice versa, it performs switching control, so on the guidance! 1
The torque of the III machine changed discontinuously within a short period of time.

This kind of torque fluctuation, which worsens the ride comfort of the elevator, occurs when the slip frequency becomes negative for a short period of time, for example, for a few losses to several 100 m5, and then becomes pressure again, that is, when the induction motor enters the regenerative state. This problem is likely to occur when the induction motor subsequently becomes inactive, and such a situation is likely to occur during upward deceleration.

This invention was made to solve the above-mentioned problems, and provides a control device for an AC elevator that can suppress rapid torque fluctuations of an induction motor that occur in a short period of time and can improve the ride comfort of the elevator. The purpose is to obtain.

[Means for Solving the Problems] An AC elevator control device according to the present invention is driven by variable voltage and variable frequency AC power supplied from an inverter, and rotates an induction motor coupled to an elevator car. A first controlling the torque of the induction motor via the inverter according to the polarity of a slip frequency command signal corresponding to a deviation between a speed signal indicating the speed and a speed command signal commanding the rotational speed of the induction motor. and a second control state in which the regenerative power of the induction motor is controlled by controlling the frequency command signal input to the inverter, and the polarity of the slip frequency command signal is reversed only for a predetermined period. When this occurs, the switching device suppresses the switching from the first control state to the second control state or vice versa.

[Function] The switching device according to the present invention suppresses the switching of the control state when the induction motor changes from, for example, power operation to short-term regenerative operation, and performs control so as to continue the current power operation. As a result, the induction motor is controlled to prevent sudden torque fluctuations.

[Example 1] An example of the present invention will be described below with reference to the drawings. Second
The figure is a block diagram of a control device for an AC elevator according to the present invention. In FIG. 1, (18c) is a switching device, and the output of the compensation structure (14), that is, the frequency command signal (14a) and the speed command (12) are input as input signals. The contacts (18a) and (18b) are switched and controlled by the output of the cutting device (18c).

In addition, in FIG. 1, the same reference numerals as those in FIG. 4 described above indicate the same or corresponding parts.

Next, the operation will be explained. The adder (13) outputs the deviation between the speed command signal (12) and the speed signal (lla). The compensation element (14) compensates for this deviation and outputs a frequency command signal (14a). Therefore.

A switching device (18e) has the property that the slip frequency command signal (14a) increases as the forward torque of the induction motor (6) increases, and its polarity becomes negative when the induction motor (6) enters regenerative operation. monitors the polarity of such a frequency command signal (14a), and when the polarity remains positive or zero for a predetermined period or more, it closes both contacts (18a) and (18b). Contact a
conversely, when the polarity becomes negative, the contacts (18a) and (18b) are both set to the contact side (second control state). However, when the switching device (18c) detects that the slip frequency command signal (14a) becomes negative only within the predetermined period, that is, only for a short period of time, the switching device @ (18c)
) switching is suppressed.

FIG. 2 is a waveform diagram showing the relationship between the slip frequency command signal (14a) and the speed command signal (12). As shown in the figure, the speed command signal (12) increases from time t to t2, becomes constant speed from time 2 to t2, and becomes constant from time t to time t.
It decreases from 4 to t5. Correspondingly, the Suberi frequency command signal (14a) changes from zero to a substantially constant first level from time t to t2, and from time t to t,
It becomes a second level lower than the first level at ~t, 4, and decreases toward zero at 1 time t4~t. However, at times t to t6, the slip frequency command signal (14a) shows a negative value, indicating that this period is a regenerative operation. As shown, this period is
M'! This period is sufficiently shorter than the time required for the jJ machine (6) to change from a constant speed state to a stopped state, or vice versa, and is shorter than a predetermined period, so switching device 1i (18c
) does not perform switching of contacts (18a) and (18b).

Note that the switching device (18c) uses the slip frequency command signal (1
4a) may be integrated, and the above-mentioned determination may be made on the integral value obtained thereby (for example, the shaded area in the figure). If there is no polar reversal in the slip frequency command signal (14a) within the integration period, this integral value is determined by the induction motor (6).
Since the load on the server increases, the state of the load can be determined from this.

Further, in the above embodiment, a case has been described in which the state of the load of the elevator is judged by the slip frequency command signal (14a) to determine whether or not switching is possible. The determination may be made based on the output of this weighing device, and the same effect as in the above embodiment can be achieved.

[Effects of the Invention] As described above, according to the present invention, according to the polarity of the slip frequency command signal corresponding to the deviation between the speed signal indicating the rotational speed of the induction motor and the speed command signal, When selecting either a first control state in which the torque of the induction motor is controlled, or a second control state in which the regenerative power of the induction motor is controlled by controlling the frequency command signal input to the inverter, When the polarity of the slip frequency command signal is reversed only for a predetermined period, switching from the first control state to the second control state or vice versa is suppressed, and the previous control state is Since the structure is configured to continue, rapid torque fluctuations of the induction motor can be reduced, and the riding comfort of the elevator can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a control device for an AC elevator according to an embodiment of the present invention, FIG. 2 is a waveform diagram of the operation of the control device for an AC elevator shown in FIG. 1, and FIG. 3 is a diagram of a conventional AC elevator control device. FIG. 4, a block diagram showing the control device, is an equivalent circuit of the induction motor (6) shown in FIG. 3. In the figure, (5) is an inverter, (6) is an induction motor, (9) is a cage, and (18c) is a switching device. Note that the same cylinder numbers in Figure 5 indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A speed signal indicating the rotational speed of an induction motor that is driven by variable frequency AC power from a variable voltage supplied from an inverter and coupled to the elevator car, and a speed command signal that commands the speed of the induction motor. a first controlling the torque of the induction motor via the inverter according to the polarity of the slip frequency command signal corresponding to the deviation between
A second controller for controlling the regenerative power of the induction motor by controlling the control state of the motor and the frequency command signal input to the inverter.
In a control device for an AC elevator having a control state, when the slip frequency command signal reverses the polarity only for a predetermined period, the control device changes from the first control state to the second control state, or vice versa. 1. A control device for an AC elevator, comprising a switching device configured to suppress switching to. (2) The switching device is configured to determine whether or not the polarity is reversed with respect to an integral value obtained by integrating the slip frequency command signal for a predetermined period.
A control device for an AC elevator as described in Section 1.