JPH0332311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rotational speed control device for an induction motor using a Servius control device.

[Background of the invention]

The configuration of a conventional induction motor rotation speed control device is shown in FIG.

In the figure, 1 is a main contactor for turning on and off the induction motor, and 2 is the induction motor.

Further, a generator 3 is attached to the induction motor 2 for detecting the number of revolutions, and the voltage generated by the generator 3 is inputted to the Cerbius control device 4.

5 is a secondary switching contactor that connects the secondary circuit of the induction motor 2 to the Servius control device 4; 6 is a secondary switching contactor that connects the secondary circuit of the induction motor 2 to the secondary resistors 7 ₁ to 7 _o It is.

8 is a control motor for increasing or decreasing the secondary resistance, 9 is a contactor that rotates the control motor 8 in a direction to decrease the secondary resistance and increase the rotation speed of the induction motor, and 10 is the control motor 8. This is a contactor that rotates the induction motor 2 in a direction that decelerates the induction motor 2.

Here, the secondary resistances ₇₁ to _7o are also used for starting the induction motor 2, and the control motor 8 sequentially decreases the resistance value to start the induction motor 2.
Accelerate and then switch to Servius operation.

This procedure will be explained in more detail.

When starting the induction motor 2, the secondary switching contactor 6 of the induction motor 2 is turned ON, and the secondary switching contactor 5 on the Serbius side is turned OFF.

Further, the secondary resistors 7 ₁ to 7 _o are kept at the starting position, that is, the position of maximum resistance. In this state, the main contactor 1 is turned on, and then the control motor 8 is rotated to sequentially decrease the secondary resistances 7 ₁ to 7 _o , and when the specified rotation speed (for example, the maximum speed) is reached, the secondary switching contact is made. 5, open the secondary switching contactor 6, and switch to Servius operation.

If the Servius control device 4 cannot be used due to a malfunction, etc., the secondary switching contactor 5 can be replaced in the above procedure.
The rotational speed of the induction motor is controlled by adjusting the resistance values of the secondary resistors 7 ₁ to 7 _o by the rotation of the control motor 8 without turning on the induction motor.

In controlling the rotation speed of such an induction motor,
Switching the operation mode during operation of the induction motor 2 has the following restrictions.

That is, first of all, when switching from operation using the secondary resistances 7 ₁ to 7 _o to operation using the Cerbius control device 4, the speed operated by the Cerbius control device 4 is the same as the induction during operation with the secondary resistances 7 ₁ to 7 _o . When the secondary switching contactor 6 is opened and the secondary switching contactor 5 is turned on when the speed is higher than the speed of the electric motor 2, the current of the inverter in the Cerbius control device 4 becomes an overcurrent, and the converter and inverter in the Cerbius control device 4 become overcurrent. The circuit breaker inserted in the circuit connecting the two will trip. However, if the induction motor 2 is operated at a higher speed than the Serbius controller 4, there is no electrical problem.

Second, when switching from operation using the Cerbius control device 4 to operation using the secondary resistances 7 ₁ to 7 _o , the rotational speed of the induction motor 2 determined by the values of the secondary resistances 7 ₁ to 7 _o is the same as the induction motor 2 before switching. If the rotation speed is higher than the rotation speed of the electric motor 2, a lash current (starting current) flows through the induction motor 2 to switch the operation mode.
The main contactor 1 may trip due to overcurrent, and the induction motor 2 may stop. However, secondary resistance 7 ₁
~7 _o If the notch is lower than the rotation of the induction motor 2, there is no electrical problem.

In either of the above two cases, even if the operation mode is switched without any electrical problems,
The rotation speed changes at the same time as switching, causing disturbance to the load on the induction motor and affecting the plant.

For this reason, conventionally, the selection of whether to control the rotation speed of the induction motor in the operation mode using the secondary resistance or the operation mode using the Cerbius control device was made before starting the induction motor, and the main The circuit is configured so that switching is not possible after the contactor is turned on, with the exception of switching from operation using the secondary resistance to operation using the Cervius control device upon completion of starting, and switching from full speed operation using the Cerbius control device to secondary resistance due to a secondary short circuit of the induction motor. There were only two cases of switching operations due to In these two cases, the rotation speed of the induction motor after switching the operation mode is clear,
This is possible because it is guaranteed in advance that the change in the rotational speed of the induction motor due to switching of the operation mode is slight.

Conventionally, in such a configuration, even if an attempt is made to switch from Servian mode to secondary resistance mode for some reason (for example, for the purpose of maintenance or modification of the Servian controller) during operation by the Servian controller, the induction motor is stopped or the induction motor is stopped at full speed. The speed increases to
The only option was to increase the secondary resistance to its final notch before switching the operating mode.

These methods cannot be used in devices where the load cannot be stopped (drinking water distribution pumps, etc.), and even if secondary resistance is provided as a backup, its effectiveness will be halved.

For this purpose, instead of the starting resistor (secondary resistor), a speed adjustment resistor (for example, using a liquid resistor) that can be used continuously is used to change the resistance value of the speed adjustment resistor. A position detector is provided to track and detect the position, and the resistance value of the speed adjusting resistor is always adjusted and on standby according to the speed of the induction motor, and when a failure occurs in the Cerbius control device, A speed control device for an induction motor using a Cerbius control device in which operation is switched from the Cerbius control device to operation using a speed adjustment resistor, and the speed adjustment resistor is adjusted according to the set speed of the speed setting device of the Cerbius control device. has been proposed (Tokuko Sho
54−5483).

However, in the above-mentioned device, although the operation mode can be switched without changing the rotational speed of the induction motor, it has the disadvantage that the hardware configuration becomes complicated.

[Purpose of the invention]

An object of the present invention is to provide an induction motor that can switch the induction motor between operation using a Servius control device and operation using a secondary resistance at an arbitrary rotation speed without changing the rotation speed of the induction motor with a simple configuration. An object of the present invention is to provide a rotation speed control device.

[Summary of the invention]

The present invention provides a rotation speed control device for an induction motor that has both a secondary resistance for rotation speed control and a Servius control device, in which the arrangement of the secondary resistance is arranged so that the rotation angle of the control motor is proportional to the rotation speed of the induction motor. By nonlinearly dividing the induction motor into two, it is possible to bumplessly switch between operation using the Servian control device and operation using the secondary resistance during operation of the induction motor.

[Embodiments of the invention]

FIG. 2 shows the configuration of an embodiment of the rotation speed control device according to the present invention. Note that the same elements as in FIG. 1 are given the same reference numerals. In the figure, a potentiometer 11 that generates an electric signal proportional to the rotation angle of the control motor 8 is attached to the control motor 8 that drives the secondary resistors 7 ₁ to 7 _o , and the output signal of the potentiometer 11 is is input to the switching control device 12. Switching control device 12
Switching control of the secondary side switching contactors 5 and 6 for switching between the Cerbius operation mode and the secondary resistance operation mode, and the switching control of the contactors 9 and 10 for increasing and decreasing the resistance values of the secondary resistances ₇₁ to _7o . Performs switching control.

Also, a generator 3 that detects the rotation speed of the induction motor 2
The output of is also input to the switching control device 12. The configuration and operation of this switching control device 12 will be described later.

The main point of the present invention is that the secondary resistances 7 ₁ to 7 in FIG.
Rather than dividing the 7 _o array evenly, it is divided non-linearly so that the rotation angle of the control motor 8 is proportional to the rotation speed of the induction motor 2.

First, FIG. 3 shows the speed characteristic curve of the induction motor 2 when the arrangement of secondary resistors is equally divided, and FIG. 4 shows the relationship between the notch and the rotation speed at this time.

The speed characteristic curve changes proportionally, so when the resistance value is multiplied by m, the horizontal axis becomes a curve multiplied by m, and the rotational speed is determined at the intersection with the load torque curve L.

In such a uniform resistance arrangement, the notch of the secondary resistance and the rotation speed of the induction motor 2 are not proportional, and in order to obtain the rotation speed from the rotation angle of the notch or control motor 8, a nonlinear compensation function generator is used. It is not always economical.

Next, in Figure 5, the resistance values of the secondary resistance are 1, 1.7, 4,
Showing the speed characteristic curve when arranged at a ratio of 20,
The relationship between the notch of the secondary resistance and the rotational speed of the induction motor 2 at that time is shown in FIG.

As is clear from these figures, if the secondary resistors are arranged so that the rotation angle of the control motor 8 and the rotation speed of the induction motor 2 are proportional, the rotation angle of the control motor 8 can be adjusted to the rotation shaft of the control motor 8. Since the rotation speed of the induction motor 2 can be detected by the value of the potentiometer 11, the switching logic of the secondary switching contactors 5 and 6 can be easily configured.

Hereinafter, a switching control device will be described which performs switching control between the operation mode by the Serbius control device 4 and the operation mode by the secondary resistance when the secondary resistances are arranged in such a non-linear manner.

In FIG. 2, first, when switching from operation using the secondary resistors 7 ₁ to 7 _o to operation using the Serbius controller 4, the rotation speed of the Serbius controller 4 is controlled by the actual rotation speed signal of the induction motor 2 until a switching operation command is issued. Hold the pattern. Then, the switching control device 12 can immediately switch the switching mode from the secondary switching contactor 6 to the secondary switching contactor 5 without causing any electrical problems or changes in the load. be exposed.

Next, when switching from the operation using the Serbius control device 4 to the operation using the secondary resistances 7 ₁ to 7 _o , when a switching operation command is issued, the rotation speed of the induction motor 2 and the potentiometer 11 are controlled by the drive of the control motor 8. Switching from the secondary switching contactor 5 to the secondary switching contactor 6 is performed at the time when the rotational speed signal of the control motor 8 detected by the rotation speed signal coincides with the rotation speed signal of the control motor 8, thereby realizing bumpless switching of the operation mode.

Specific means for realizing the above functions will be described next.

First, the switching operation from the operation using the secondary resistors ₇₁ to _7o to the operation using the Servius control device 4 will be explained with reference to FIG. In the figure, a rotation speed setting follow-up circuit 20 of the Servius control device 4 includes a changeover switch 21 and an analog memory 22.

While the induction motor 2 is operating in the secondary resistance mode, the contents of the analog memory 22 follow the actual rotation speed of the induction motor 2, so the rotation speed pattern to the Servius control device 4 matches the actual rotation speed. The switching from the secondary switching contactor 6 to the secondary switching contactor 5 is carried out immediately.

Second, the switching operation from the operation using the Servius control device 4 to the operation using the secondary resistors 7 ₁ to 7 _o will be explained with reference to FIG. 8. In the figure, contactors 5 and 42 are first in the ON state, and contactors 6 and 6 are in the ON state.
When the induction motor 2 enters the Serbius mode operation state, the secondary resistance 7 ₁
~7 _o is increased to excite the excitation coil 34L of the contactor 10, which decreases the rotational speed of the induction motor 2.

As a result, the secondary resistance returns to its maximum position (the lowest rotational speed).

Next, the excitation coil 3 that drives the contactor 9 when the mode switching operation to operation is performed on the secondary resistance 7 ₁ to 7 _o .
4R is excited, thereby forcing the control motor 8 that drives the secondary resistors 7 ₁ to 7 _o to rotate in the speed increasing direction. This speed increase continues until the comparator 31 operates.

On the other hand, this forced speed-up only requires a certain period of time after switching to the operation mode using the secondary resistors 7 ₁ to 7 _o , and a cut circuit is incorporated therein depending on the timer 33.

Furthermore, a potentiometer 1 indicates the output voltage of the generator indicating the actual rotation speed of the induction motor 2, and the rotation angle of the control motor 8 that drives the secondary resistors ₇₁ to _7o .
1 output voltage is input to the comparator 31,
This comparator detects whether the two power voltages match.

On the other hand, when the induction motor 2 is switched to the operation mode using the secondary resistors 7 ₁ to 7 _o while being operated by the Serbius control device 4, the rotational speed of the induction motor 2 and the rotational speed of the secondary resistors 7 ₁ to 7 _o match. At this point, the excitation coil 6 is excited by the output of the comparator 31, and the contactor 6 is turned on. As a result, the contact point 34
OFF, the excitation coil 42 is deenergized, the contactor 5 is turned OFF, and the operation is switched from the Serbius control device 4 to the operation using the secondary resistors 7 ₁ to 7 _o .

As explained above, according to this embodiment, in an induction motor that has both a Servian control device for rotation control and a secondary resistance, switching between the Servian operation mode and the secondary resistance operation mode is possible with a simple hardware configuration. This can be done without affecting the rotation speed.

〔Effect of the invention〕

According to the present invention, there is provided a simple rotational speed control device that can switch an induction motor between operation using a Servian control device and operation using a secondary resistance at an arbitrary rotational speed without changing the rotational speed of the induction motor. This can be achieved with a hardware configuration.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional rotation speed control device for an induction motor, Fig. 2 is a block diagram showing an embodiment of the rotation speed control device according to the present invention, and Fig. 3 is a block diagram showing an example of the arrangement of secondary resistances. Figure 4 is a diagram showing the relationship between the secondary resistance notch and the rotation speed of the induction motor in this case, and Figure 5 is a diagram showing the speed characteristics of the induction motor when divided into A diagram showing the speed characteristics when divided, Figure 6 is a diagram showing the relationship between the notch of the secondary resistance and the rotation speed of the induction motor in this case, and Figure 7 is a diagram showing the configuration of the main parts of the Cerbius control device. , FIG. 8 is a block diagram of the switching control device. 2... Induction motor, 3... Generator, 4... Servius control device, 5, 6... Secondary switching contactor, 7 ₁ to 7 _o ...
Secondary resistance, 8... Control motor, 11... Potentiometer, 12... Switching control device.

Claims (1)

[Claims] 1. A Servius control device and a secondary resistance connected to the secondary side of the induction motor via a switching means, a control motor that adjusts the resistance value of the secondary resistance, and an electric signal proportional to the rotation angle of the control motor. a signal generator that generates a rotation speed, a rotation speed detection means that detects the rotation speed of the induction motor, and a rotation speed detection means that takes in the outputs of the signal generator and the rotation speed detection means so that the induction motor can reach an arbitrary rotation speed while being operated by the Cerbius control device. When switching to the operation mode using secondary resistance, the secondary side of the induction motor is connected to the secondary resistance side when the rotation speed corresponding to the rotation angle of the control motor matches the rotation speed of the induction motor. In the rotation speed control device for an induction motor having a control means for switching the switching means, the arrangement of the secondary resistances is nonlinearly divided so that the rotation angle of the control motor and the rotation speed of the induction motor are proportional. A rotation speed control device for an induction motor, characterized by: