CN101615873A - Frequency relay - Google Patents

Abstract

The invention discloses a frequency relay, which is characterized by comprising: the device comprises a frequency measuring circuit, a setting input unit, a relay unit and a control unit; after receiving the frequency signal of the YZR motor rotor sent back by the frequency measuring circuit, the frequency signal is converted into a specific frequency value to be compared with a frequency set value of the YZR motor rotor which is input by a setting input unit and enables the relay to operate, and when the frequency of the YZR motor rotor sent back by the frequency measuring circuit reaches the frequency set value, a control signal is sent to the relay unit to enable the relay in the relay unit to operate. Compared with the traditional control mode of a YZR type three-phase asynchronous winding type motor, the switching device provided by the invention has the advantage that the frequency relay is more accurately controlled than the time relay. In addition, the motor rotor resistance switching device is simple in structure, convenient to produce, low in cost and suitable for wide popularization in the field of motor rotor resistance switching.

Description

frequency relay

technical field

The invention relates to a YZR motor rotor resistance switching device, in particular to a frequency relay which uses a frequency relay to control the YZR motor rotor resistance switching.

Background technique

YZR three-phase asynchronous wound motors are often used in industrial equipment such as metallurgical machinery and cranes. In the control of YZR three-phase asynchronous wound motor, resistors need to be connected in series in the rotor circuit to control its starting torque and reduce its starting current. However, when the YZR three-phase asynchronous wound motor needs to run at full speed, it is necessary to cut off the resistance connected in series in the rotor circuit. Cutting needs to be switched step by step. At present, the traditional control of YZR three-phase asynchronous wound motor rotor resistance is cut off step by step by using the delay function of the time relay. Since the delay time of the time relay is set artificially based on experience, as shown in Figure 1, it is a schematic diagram of the principle of traditional gear control resistance switching. When the time relay of the S1 gear reaches the closing time, it is considered that the motor reaches the S1 gear control speed. , the gear position S1 is closed (equivalent to short-circuiting S1), so that the gears S1, S2, S3 and S4 are switched sequentially when the motor reaches the rated speed, so as to limit the motor current to not exceed the standard. This kind of control is often accompanied by the fact that the set time is too short, and the resistance is cut off prematurely, so that the switching current of the motor exceeds its allowable maximum current, causing the motor to heat up seriously, and the torque of the motor will exceed the starting torque, which will give a great impact to the mechanical mechanism. , shorten the life of the entire transmission chain. If the set time is too long and the resistance is cut off too late, the starting time will be too long, which is not conducive to the use and control of the equipment, and reduces the efficiency of the equipment. As shown in Figure 3, the control effect of the motor rotor cut resistance time relay control mode As shown in the figure, when the actual motor switches the rotor resistance, the switching torque and current impact it bears are extremely irregular (see paragraphs ab, cd, ef, gh), and in most cases it is far greater than the rated value of the motor. This is because the switching condition is controlled by the time relay, but in practice, the adjustment of the time relay is completely based on empirical values (see bc, de, fg paragraphs), which is not very accurate. In addition, due to the different action of the load in different running directions, the adjustment of the time is more difficult. In the downward direction, because the load is the acceleration torque, the deceleration of the motor is large, and the setting time is short, which is beneficial to the motor. But in the upward direction, Since the load is a resistance torque, the deceleration of the motor is small, and the setting time is short, which is the same as the resistance load, or even worse. Conversely, if the setting time is long, it may be suitable in the upward direction, but in the downward direction, the long time will cause the motor to run at an overspeed, which will bring unsafe operation to the equipment.

Contents of the invention

In view of the above problems, the present invention develops a control device based on the traditional resistance cutting control mode of the motor, and takes the motor rotor frequency as the resistance cutting condition. The specific technical means are as follows:

A frequency relay is characterized in that it comprises:

The frequency measurement circuit is used to filter the input frequency signal of the YZR motor rotor, filter out the harmonic component, DC component and interference signal, and perform analog/digital conversion after the restored signal is amplified. The digital signal is transmitted to the control unit;

Set the input unit, which is used to input the setting signal to the control unit, that is, the frequency setting value of the rotor of the YZR motor whose relay operates;

The relay unit, after receiving the control signal, closes the corresponding open point or opens the closed point to realize the connection or cut-off of the rotor resistance;

The control unit, after receiving the frequency signal of the YZR motor rotor returned by the frequency measurement circuit, converts it into a specific frequency value, making it the same as the frequency setting value of the YZR motor rotor input by the setting input unit to make the relay act. In comparison, when the frequency of the YZR motor rotor returned by the frequency measurement circuit reaches the above-mentioned frequency setting value, a control signal is sent to the relay unit to make the relay in the relay unit act.

The relay unit includes more than one relay, and the corresponding setting input unit can input more than one frequency setting value of the rotor of the YZR motor to activate the relay to the control unit.

The control unit also detects the frequency of the rotor of the YZR motor to judge the running state of the motor. When it is in the corresponding gear position, the detected frequency is far from the actual set value, and the display unit prompts an alarm, and controls the power switch for power-off protection .

Compared with the traditional control method of YZR type three-phase asynchronous winding motor, the frequency relay provided by the present invention has more precise control than the time relay. Corresponding control, so that no matter what the situation, the resistance switching point is a fixed switching point. Setting an appropriate switching point can speed up the speed response time of the motor without causing the motor to suffer from overload and overcurrent, which greatly improves the operation safety of the motor. The frequency relay can also be used to protect the running state of the motor. When the motor is running in a certain state, it can be judged whether it is in a controlled state by detecting the rotor frequency of the motor. When it is out of control, it can prompt an alarm and perform power-off protection. In addition, the structure is simple, easy to produce and low in cost, and is suitable for wide popularization in the field of motor rotor resistance switching.

Description of drawings

Figure 1 is a schematic diagram of the principle of traditional gear position control resistor switching;

Fig. 2 is a schematic structural view of the switching device of the present invention;

Fig. 3 is a schematic diagram of the implementation process of the motor rotor cutting resistance adopting the time relay control mode;

Fig. 4 is a schematic diagram of the frequency setting value of the embodiment of the switching resistance of the present invention being a single resistance;

Fig. 5 is a schematic structural diagram of an embodiment of a single-resistor switching device according to the present invention;

Fig. 6 is a schematic diagram of the frequency setting value of the embodiment of the present invention where the switching resistance is four resistances;

Fig. 7 is a schematic structural diagram of an embodiment of the switching resistance of the present invention with four resistance switching devices;

Fig. 8 is a schematic diagram of the implementation process of using the time relay control method to cut the resistance of the motor rotor.

Detailed ways

As shown in Figure 2, the frequency relay includes: it is used to filter the input frequency signal of the YZR motor rotor, filter out the harmonic component, DC component and interference signal, and amplify the restored signal Carry out analog/digital conversion and transmit the converted digital signal to the frequency measurement circuit in the control unit; it is used to input the setting signal to the control unit, even if the relay operates the setting input unit of the frequency setting value of the YZR motor rotor; it is used for After receiving the control signal, the corresponding open point is closed or the closed point is opened to realize the relay unit that connects or cuts off the rotor resistance; and after receiving the frequency signal of the YZR motor rotor returned by the frequency measurement circuit, the It is converted into a specific frequency value, and compared with the frequency setting value of the YZR motor rotor input by the setting input unit to make the relay operate, when the frequency of the YZR motor rotor returned by the frequency measurement circuit reaches the above frequency setting value , A control unit that sends a control signal to the relay unit to make the relay in the relay unit act. The frequency measurement circuit is an integrated circuit of an isolation circuit, a filter and an analog/digital converter; the input unit is set as an external input device, which can be realized by using a touch screen integrated with a display unit and an input unit; the relay unit can use more than one For the relay group, the corresponding setting input unit can also input more than one frequency setting value of the YZR motor rotor that makes the relay act to the control unit to control the switching of different gears of the motor resistance; the control unit is the main control device, which can be Processing equipment such as single-chip microcomputer and PLC, the following embodiments adopt single-chip microcomputer to realize.

Embodiment 1: As shown in Figure 4 and Figure 5, it is a single-speed control of the motor. When measuring, connect the detection input end of the frequency measurement circuit to the rotor terminal of the YZR three-phase asynchronous wound motor, and pass through the frequency measurement circuit. The filter filters out the harmonic component, DC component and interference signal in the input voltage signal to restore the frequency of the power supply under test. After being processed by the op amp and analog/digital conversion, it is handed over to the single chip microcomputer for processing and calculation, and finally calculates The frequency of the power supply is compared with the switching frequency value input by the single-chip microcomputer according to the setting input unit. When the measured frequency reaches the set value, the single-chip computer controls the corresponding relay action to complete the control of gear switching (as shown in Figure 4 Indicates that when the frequency reaches point a, the controller sends a control signal to the relay, and the corresponding relay completes the switching of the resistance).

Embodiment 2: As shown in Fig. 6, Fig. 7 and Fig. 8, its wiring mode and device setting are the same as those of Embodiment 1, the difference is that the switching control of 4 gears is used here, that is, the relay unit 4 relays are required to complete the switching tasks of 4 gears, and the input unit is set accordingly to input the frequency values of 4 suitable switching points. As shown in Figure 6, four switching points a, b, c and d are input to the controller by setting the input unit. It is an automatic process to complete the resistance switching of the YZR three-phase asynchronous wound motor with this device, as shown in In the case of switching rotor resistance shown in Figure 8, it can be seen that when the actual motor switches rotor resistance, the switching torque and the current it bears are extremely regular (see paragraphs ab, cd, ef, and gh). Through parameter setting, your motor can have sufficient torque when the rotor resistance is switched, and the motor rotor current can also be controlled within an appropriate range.

In addition, the control unit also detects the frequency of the rotor of the YZR motor to judge the running state of the motor. When it is in the corresponding gear, the detected frequency is far from the actual set value, and the display unit prompts an alarm, and controls the power switch for power-off protection. .

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (3)

1, a kind of frequency relay is characterized in that comprising:

Frequency measurement circuit, be used for will input the frequency signal of YZR motor rotor carry out Filtering Processing, harmonic component, DC component and interference signal are filtered, and the signal after the reduction is carried out carrying out after the processing and amplifying digital data transmission after mould/number conversion will be changed in control unit;

Input unit is set, is used for to control unit input setting signal, even the frequency setting value of the YZR motor rotor of the actuating of relay;

Relay unit is receiving opening of the closure of making war accordingly after the control signal or close point, rotor resistance is connected or cut away realizing;

Control unit, behind the frequency signal that receives the YZR motor rotor that frequency measurement circuit passes back, be translated into concrete frequency numerical value, its frequency setting value with the YZR motor rotor that makes the actuating of relay that the input unit input is set is compared, after the frequency of the YZR motor rotor that frequency measurement circuit is passed back reaches the said frequencies set point, send control signal to relay unit, make the actuating of relay in the relay unit.

2, a kind of frequency relay according to claim 1, it is characterized in that comprising in the described relay unit more than one relay, the corresponding setting input unit can be imported the more than one frequency setting value that makes the YZR motor rotor of the actuating of relay to control unit.

3, a kind of frequency relay according to claim 1; it is characterized in that described control unit is also by detecting the frequency of YZR motor rotor; to judge the running status of motor; when at corresponding gear; detection frequency and actual set value differ far and report to the police by the display unit prompting, and the control mains switch carries out power-off protection.

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