JPS6321429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for controlling an elevator driven by an induction motor.

There is an elevator car in which an induction motor is used as an electric motor to drive the car, and by controlling the slip frequency of the induction motor, the torque of the electric motor is controlled to drive the car. This is shown in FIGS. 1 and 2.

In the figure, 1 is a three-phase AC power supply terminal, 2 is an electromagnetic contactor contact that is connected to terminal 1 and closes when the car 11 is started and opens when the car 11 is stopped, which will be described later. 4 is a smoothing capacitor connected to the DC side of the converter 3, 5 is a resistor whose one end is connected to one end of the smoothing capacitor 4, and 6 is the other end of the resistor 5 and the smoothing capacitor 4. transistor connected to the other end,
7 is an inverter connected to both ends of the smoothing capacitor 4 and configured with transistors and diodes, which is a well-known pulse width modulation type inverter that converts a constant DC voltage into AC of an arbitrary voltage and arbitrary frequency;
1 is a three-phase induction motor driven by an inverter 7; 9 is a driving sheave of a hoist driven by an electric motor 8; 10 is a main rope wound around the sheave 9;
Reference numerals 1 and 12 denote a car and a counterweight respectively connected to both ends of the main rope 10, 13 a generator for a speedometer which is connected to the electric motor 8 and emits a speed signal 13a indicating the rotational speed of the electric motor 8, and 14 a speed command signal. , 15
is an adder that outputs a deviation signal between the speed command signal 14 and the speed signal 13a, 16 is a compensation element connected to the adder 15 to improve the response of the speed control system, G(s) is a transfer function, and 16a is compensation element 16
17 is an adder that outputs the sum of the slip frequency command signal 16a and the speed signal 13a, 18 is a voltage command generator that outputs a voltage command signal 18a from the output of the adder 17, and 19 is the same. A frequency command generator 20 that emits a frequency command signal 19a is an inverter control device that controls the output voltage and output frequency of the inverter 7 based on the voltage command signal 18a and the frequency command signal 19a.

That is, the speed command signal 14 and the speed signal 13a
A slip frequency command signal 16a corresponding to the deviation is output, and this slip frequency command signal 16a corresponds to a torque command signal. By adding the speed signal 13a to this by the adder 17, the voltage command signal 18a and the frequency command signal 19
a can be determined. Based on these command values, the control device 20 performs switching control on the elements of the inverter 7 (and in some cases, the converter 3 when the converter 3 is composed of a thyristor, etc.),
The electric motor 8 is caused to generate a torque corresponding to the slip frequency command signal 16a. The electric motor 8 is now activated and the car 11 runs, and its speed is automatically controlled with high precision.

FIG. 2 shows a curve 21 of torque versus rotational speed of the electric motor 8. Here, n ₀ is the synchronous speed, which is the operating point when the motor 8 rotates at a rotational speed corresponding to the output frequency of the inverter 7. Generally, in an induction machine, near the synchronous speed n ₀ , the torque is proportional to the slip frequency (e.g. corresponds to n ₀ −n ₁ or n ₀ −n ₂ ). Therefore, the quantity n ₀ corresponding to slip x frequency
If −n ₁ is controlled, the torque can be controlled.

Now, in the case of an elevator, when the car 11 is decelerated to a stop, when the car 11 is caused to descend at a constant speed with a heavy load, etc., the electric motor 8 must generate a braking force. This is shown in FIG. 2 for a case where the required braking torque is _T2 . In this case, the rotational speed n ₂ of the electric motor 8 is higher than the synchronous speed n ₀ . In such operation, mechanical energy is converted to electrical energy via the electric motor 8, and regenerated power is returned to the DC side via the inverter 7. Therefore, there is a possibility that the DC side voltage increases and the elements in the inverter 7 are destroyed. A resistor 5 protects this, and when the transistor 6 is turned on, the regenerated power is consumed by the resistor 5. Also, resistance 5
In some cases, a regenerative inverter is installed instead, and the regenerated power is returned to the power source.

However, in either case, it is inevitable that the regenerative power processing device will be expensive.

This invention aims to improve the above-mentioned problems, and has a special device that controls the torque by controlling the slip frequency when the electric motor is running in power, and controls the regenerative power by controlling the frequency during regenerative braking. An object of the present invention is to provide a control device for an AC elevator that can process regenerated power without any problems.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

In the figure, 23 is a switching device that brings contacts 23a and 23b into contact with contact point a when the sliding frequency command signal 16a is positive (including zero), and brings them into contact with contact point b when the signal 16a becomes negative; Contact 23
A gain converter is connected between contact b of contact a and the control device 20 and outputs a value set according to the input value; 25 is a gain converter connected between contact b of contact 23b and the control device 20;
This is a power control device connected between Other than the above, the configuration is the same as in FIG. 1.

Next, the operation of this embodiment will be explained.

First, the principle will be explained with reference to FIG.

FIG. 4 is a well-known Highland circle diagram that can graphically determine the characteristics of an induction motor.

In the figure, points P ₀ -P ₁ -P _n are the power running region (induction motor region), and points P _n -P ₂ -P ₃ -P _e are the regenerative braking region (induction generator region). For example, when the electric motor 8 is operating at point _P1 , the electrical input is proportional to P1 _{- c1} , the generated torque is proportional to _P1 - _b1 , and the mechanical output is proportional to _P1 - _a1 . Also, when driving at point P ₂ in the regenerative braking region, the electrical output is P ₂ −c ₂ and the generated torque is P ₂
−b ₂ , the mechanical input is proportional to P ₂ −a ₂ , respectively.
The slips are a ₁ b ₁ /P ₁ b ₁ and a ₂ b ₂ /P ₂ b ₂ , respectively. Now, when the electric motor 8 is operated at point _P3 , the electrical output is zero, the generated torque is _P3 - _b3 , the mechanical input is _P3 - _a3 , and the slip is _a3b3 / _{P3 .} b ₃ .
In other words, if the operating point is set to _P3 , the motor 8 can generate braking force without transmitting or receiving active power. The magnitude of the generated torque can be controlled by controlling the magnitude of the circle diagram, that is, the voltage. Note that another operating point at which braking force can be obtained without transfer of active power can be found from the same figure as the point where the circle intersects with the horizontal axis, but this is not practical because the braking torque is limited.

When the electric motor 8 is running, the deviation between the speed command signal 14 and the speed signal 13a is positive, the slip frequency command signal 16a is positive, and the switching device 23 does not operate.
Since the contacts 23a and 23b are both in contact with the contact point a, the operation in FIG. 3 is similar to that in FIG. 1.

When the electric motor 8 enters braking, the slip frequency command signal 16a becomes negative, so the switching device 23 operates,
Both contacts 23a and 23b are switched to contact b. Now, the power control device 25 inputs the speed signal 13a, and outputs a frequency command signal such that the regenerated power becomes zero to the control device 20. On the other hand, the slip frequency command signal 16a is transmitted to the gain converter 2
4, and its output is output to the control device 20 as a voltage command signal.

Here, if the frequency at which the regenerated power becomes zero is determined from the equivalent circuit of the induction motor shown in FIG. 5, it can be seen that it is independent of the applied voltage.

In Fig. 5, the power consumed inside the electric motor 8 is P ₁
is P ₁ = V ² g ₀ + r ₁ (V/Z) ² + r ₂ (V/Z) ² ... However, Z = √ ( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² ... Here, V : AC input voltage Z : Total impedance of the motor 8 g ₀ : Excitation conductance r ₁ , r ₂ : Primary resistance and secondary resistance of the motor 8 (primary conversion value) x ₁ , x ₂ : Primary leakage reactance and secondary resistance of the motor 8 Next leakage reactance (primary conversion value) s: Slip of electric motor 8 On the other hand, the electric power P _g generated as regenerative power is P _g = (V/Z) ²・(1-s/s) r ₂ ... Here, P If the slip s is controlled so that ₁ +P _g =0..., all the mechanical energy will be consumed inside the electric motor 8.

Substituting the formula and formula into the formula, s = r ₂ / r ₁ + g ₀ Z ² ... However, Z = Z (s), and by finding s that satisfies the formula regardless of the input voltage V, power transfer and reception can be performed. If the slip s that generates the braking force is determined without the inverter 7 and the speed signal 13a is given, the frequency command signal to the inverter 7 is determined. Therefore, it can be seen that only the speed signal 13a needs to be given to the power control device 25. Note that b ₀ in the figure is the excitation susceptance.

Now, when the contacts 23a and 23b are switched, the frequency command signal in which no regenerative power is generated and the voltage command signal corresponding to the slipping frequency command signal are respectively given to the inverter 7, as described above. At this time, if the above switching is performed when the sliding frequency command signal 16a is zero, the voltage immediately after switching is zero, so even if the frequency is switched in a stepwise manner, the torque will not change in a stepwise manner. There is no change, and the torque smoothly transitions from powering torque to braking torque.

FIG. 6 shows another embodiment of the invention.

In this embodiment, the third
It is similar to the figure.

In the simple equivalent circuit shown in Fig. 5, slippage without transfer of active power is generally required regardless of the applied voltage, but when considering the nonlinearity of the iron core, the switching loss of the inverter 7, etc., the above slippage has no effect. Therefore, the power control device 25 calculates the slippage without the transfer of active power using the applied voltage and speed as inputs.

Note that the calculated results are stored in a storage device (not shown).
It is also possible to output a required frequency command signal depending on the voltage and speed.

As explained above, in this invention, when driving an induction motor that operates a car by replacing DC power with AC power using an inverter, when the motor is running, a torque signal corresponding to the deviation between the speed command signal and the speed signal is used to generate a torque. During regenerative braking, the speed signal controls the frequency command signal given to the inverter so that the absolute value of motor slippage is greater than the value determined by the formula, and this switching is controlled by the torque command signal. Since the switching is performed when the torque reaches zero, the regenerated power can be processed without any special equipment, and this switching can be performed smoothly without any torque fluctuation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional AC elevator control device, FIG. 2 is a torque characteristic curve diagram of the induction motor of FIG. 1, and FIG. 3 is an embodiment of an AC elevator control device according to the present invention. The configuration diagram, Figure 4, is the Highland circle diagram of the induction motor in Figure 3, and Figure 5.
This figure is also a simplified equivalent circuit diagram, and FIG. 6 is a block circuit diagram showing another embodiment of the present invention, which corresponds to the circuit portion of FIG. 3. 3...Converter, 4...Smoothing capacitor, 7
...Inverter, 8...Three-phase induction motor, 11...
... Car, 13 ... Speedometer generator, 13a ... Speed signal, 14 ... Speed command signal, 15, 17 ...
Adder, 18... Voltage command generator, 19... Frequency command generator, 20... Inverter control device, 2
3...Switching device, 25...Power control device. In addition,
Identical parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1. Connecting a DC power source to an inverter to convert the DC power into AC power with variable voltage and variable frequency, and using the converted AC power to drive an induction motor to operate the car. A first means for controlling the torque of the electric motor by a torque command signal according to a deviation between a speed command signal and a speed signal of the electric motor, and a first means for controlling a frequency command signal given to the inverter by the speed signal. , where the primary resistance value of the motor is r ₁ , the primary conversion value of the secondary resistance is r ₂ , the excitation conductance is g ₀ , and the total impedance is Z, the absolute value of the slip of the motor is r ₂ /r ₁ +g The second value is controlled to be larger than the value determined by ₀ Z ² .
means, and a switching means for using the first means when the torque command signal is positive and switching the first means to the second means when the torque command signal becomes zero. A control device for an AC elevator, characterized in that: