CN211183845U - Frequency conversion switching power frequency device for motor dragging load - Google Patents
Frequency conversion switching power frequency device for motor dragging load Download PDFInfo
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- CN211183845U CN211183845U CN201922234230.5U CN201922234230U CN211183845U CN 211183845 U CN211183845 U CN 211183845U CN 201922234230 U CN201922234230 U CN 201922234230U CN 211183845 U CN211183845 U CN 211183845U
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Abstract
The utility model discloses a frequency conversion switching power frequency device for motor drags load, the circuit comprises a main circuit, a control system, control system makes main pump motor M be in the mode of raising the frequency through selecting the suitable reduction gear of velocity ratio during normal operating mode during operation, set up programmable controller P L C, speed sensor, the timer, when realizing main pump motor M outage back rotational speed to 75% quota rotational speed, the automatic output separating brake instruction is to high-pressure vacuum contactor KM1 in the main circuit, KM2, treat to receive high-voltage switch QF1, high-pressure vacuum contactor KM2 separating brake state and time delay Tc time after the automatic output high-pressure vacuum contactor KM3 switching-in instruction realizes the frequency conversion and cuts the power frequency, Tc represents the shift time, by calculating the time value that main pump motor M outage back rotational speed drops to the quota rotational speed more than 75%, then finely tune on the basis of numerical value, guarantee to obtain with the phase place is unanimous in the phase place of main pump motor M induced electromotive force at the shift moment, realize.
Description
Technical Field
The utility model relates to a frequency conversion switches power frequency control technical field, especially is used for the motor to drag the frequency conversion of load and switches power frequency device.
Background
In the industrial application field, the starting and the speed regulation of high-power heavy-load equipment generally adopt a mode of dragging a high-voltage asynchronous motor by a high-voltage frequency converter, for some equipments requiring high reliability and stability in the process flow, users usually require the high-voltage inverter to be equipped with an automatic power frequency switching device, so that the high-voltage inverter can be automatically switched to a power frequency bypass operation when the inverter fails, therefore, the continuous operation of the production equipment is ensured to the maximum extent, but in practical application, various factors (the rotating speed of the motor is reduced, the influence of the induced electromotive force of the stator of the motor) cause great impact to be generated in the switching process, particularly when a high-power motor drags a heavy-load low-speed constant-torque load, due to the load characteristic, the rotating speed of the motor is reduced quickly after power failure, and if the switching time Tc is not properly selected, a large impact is generated in the switching process, so that the normal operation of a power grid and the service life of equipment are influenced.
Therefore, the utility model provides a new scheme to solve the problem.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a not enough to prior art exists, the utility model aims at providing a frequency conversion switches power frequency device for motor drags load, has solved effectively and has produced very big problem of assaulting by frequency conversion automatic switch to power frequency in-process when solving high-power motor and taking this type of load.
The technical scheme includes that the main circuit comprises a main circuit and a control system, wherein the main circuit comprises a high-voltage switch QF1, a frequency converter cabinet VFD, an automatic power frequency bypass cabinet BY and a main pump motor M, and the main circuit is characterized in that the automatic power frequency bypass cabinet BY comprises a disconnecting link isolating switch QS1, a disconnecting link isolating switch QS2, a high-voltage vacuum contactor KM1, a high-voltage vacuum contactor KM2 and a high-voltage vacuum contactor KM3, and the automatic power frequency bypass cabinet BY realizes the switching of the operation of the frequency converter to the operation of a power frequency power grid under the control of the control system.
Preferably, one end of the high-voltage switch QF1 is connected with a 6KV bus, the other end of the high-voltage switch QF1 is divided into two paths, one path is connected to the left end of the frequency converter through a high-voltage vacuum contactor KM1 and a disconnecting switch QS1, the other path is connected to the left end of the automatic power frequency bypass cabinet BY, the right end of the automatic power frequency bypass cabinet BY is connected with one end of a normally open contact of a high-voltage vacuum contactor KM3, the right end of the frequency converter is connected with one end of a normally open contact of a high-voltage vacuum contactor KM2 through a disconnecting switch QS2, the other end of the normally open contact of the high-voltage vacuum contactor KM3 and the.
Preferably, the control system comprises a speed reducer, and the main pump motor M is in an up-conversion mode when working under normal working conditions by selecting the speed reducer with a proper speed ratio;
the control system comprises a programmable controller P L C, a rotating speed sensor and a timer, and is characterized in that when the rotating speed of a main pump motor M reaches 75% of limit rotating speed after power failure, switching-off instructions of the high-voltage vacuum contactor KM1 and the high-voltage vacuum contactor KM2 are automatically output, and after receiving the switching-off states of the high-voltage switch QF1 and the high-voltage vacuum contactor KM2 and delaying Tc time, a switching-on instruction of the high-voltage vacuum contactor KM3 is automatically output to realize frequency conversion and power frequency switching, wherein Tc represents switching time.
The utility model discloses an at first select the suitable reduction gear of velocity ratio to make main pump motor M be in the mode of raising frequency at normal operating mode during operation, secondly set up programmable controller P L C, speed sensor, the time-recorder, when realizing rotational speed to 75% quota rotational speed after main pump motor M outage, automatic output high pressure vacuum contactor KM1, high pressure vacuum contactor KM2 separating brake instruction, treat to receive high tension switch QF1, high pressure vacuum contactor KM2 separating brake state and time delay Tc time after automatic output high pressure vacuum contactor KM3 combined floodgate instruction realize frequency conversion and cut the power frequency, Tc represents switching time, by calculating the time value that main pump motor M outage back rotational speed falls to the quota rotational speed more than 75%, then finely tune on the basis of numerical value, guarantee phase place and the unanimous gained of mains voltage phase place of motor M response electromotive force constantly switching, with this realization frequency conversion automatic smooth switch to operation.
Drawings
Fig. 1 is a main circuit structure diagram of the present invention.
Detailed Description
The foregoing and other technical and scientific aspects, features and advantages of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying fig. 1. The structural contents mentioned in the following embodiments are all referred to the attached drawings of the specification.
Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.
The frequency conversion power frequency switching device for the motor to drive the load comprises a main circuit and a control system, wherein the main circuit comprises a high-voltage switch QF1, a frequency converter cabinet VFD, an automatic power frequency bypass cabinet BY and a main pump motor M, and is characterized in that the automatic power frequency bypass cabinet BY comprises a disconnecting switch QS1, a disconnecting switch QS2, a high-voltage vacuum contactor KM1, a high-voltage vacuum contactor KM2 and a high-voltage vacuum contactor KM3, the automatic power frequency bypass cabinet BY realizes that the main pump motor M automatically outputs a switching instruction of the frequency converter to the power frequency power network when the frequency converter fails under the control of the control system, the specific control system immediately and automatically outputs a switching-off instruction of the high-voltage vacuum contactor KM1 and the high-voltage vacuum contactor KM2, and automatically outputs a switching-on instruction of the high-voltage vacuum contactor KM2 after receiving the switching-off state of the high-voltage switch QF1 and the high, when the received switching-on states of QF1 and KM3 indicate that the process of frequency conversion and power frequency switching is finished, an alarm signal is output at the same time.
Furthermore, one end of the high-voltage switch QF1 is connected with a 6KV bus, the other end of the high-voltage switch QF1 is divided into two paths, one path is connected to the left end of the frequency converter through a high-voltage vacuum contactor KM1 and a disconnecting switch QS1, the other path is connected to the left end of the automatic power frequency bypass cabinet BY, the right end of the automatic power frequency bypass cabinet BY is connected with one end of a normally open contact of the high-voltage vacuum contactor KM3, the right end of the frequency converter is connected with one end of the normally open contact of the high-voltage vacuum contactor KM2 through a disconnecting switch QS2, the other end of the normally open contact of the high-voltage vacuum contactor KM3 and the other end of the normally open contact of the high-voltage vacuum contactor KM2 are connected to the main pump motor M, and a frequency conversion mode is selected when the high-voltage switch QF 1; the high-voltage switch QF1 and the high-voltage vacuum contactor KM3 are closed, the high-voltage vacuum contactors KM1 and KM2 are operated at power frequency when disconnected, the disconnecting switch QS1 and QS2 are disconnected when the frequency converter is overhauled, personnel are prevented from getting electric shock, and because the output end of the frequency converter is not allowed to be connected with a power supply, very reliable interlocking measures need to be taken for the high-voltage vacuum contactors KM2 and KM 3.
Further, the control system comprises a speed reducer, the main pump motor M is in an up-conversion mode when working under normal working conditions by selecting the speed reducer with a proper speed ratio, and the application of the coal oil slurry feeding pump is taken as an example as follows:
m-6 level frequency conversion and frequency modulation of a main pump motor are 0-75 Hz and 50-987 rpm/min;
reducer ratio-15.389: 1;
normal pump condition-flow 24-60 m3H, outlet pressure: 20.1Mp, pump speed: 33 to 83 rpm/min.
According to the corresponding relation between the flow rate and the rotating speed of the pump and the rotating speed of the motor, calculating the time-varying frequency modulation range of the normal working condition of the pump: 25.9-65 Hz, actually measuring the output power of the motor: 158.2-397 KW.
Selecting a speed reducer with the speed ratio of 15.389:1, and when the oil-coal slurry feeding pump works at the maximum flow rate of 60m3When the speed is/h, the main pump motor M operates at 65 Hz;
the control system comprises a programmable controller P L C, a rotating speed sensor and a timer, and is characterized in that when the rotating speed of a main pump motor M reaches 75% of limit rotating speed after power failure, switching-off instructions of the high-voltage vacuum contactor KM1 and the high-voltage vacuum contactor KM2 are automatically output, and after receiving the switching-off states of the high-voltage switch QF1 and the high-voltage vacuum contactor KM2 and delaying Tc time, a switching-on instruction of the high-voltage vacuum contactor KM3 is automatically output to realize frequency conversion and power frequency switching, wherein Tc represents switching time.
Furthermore, the Tc time is calculated by calculating a time value of the rotational speed of the main pump motor M after power failure decreasing to 75% or more of rated rotational speed, and then fine-tuned on the basis of the numerical value to ensure that the phase of the induced electromotive force of the main pump motor M at the time of switching is consistent with the phase of the power supply voltage, the impact current is mainly affected by slip from the operation with the power frequency and the induced electromotive force of the motor, the process of switching the power frequency in a variable frequency manner is that firstly the rotational speed of the motor after power failure is detected by a rotational speed sensor, the programmable controller P L C and a timer calculate the time value of the rotational speed of the motor after power failure decreasing to 75% or more of rated rotational speed, then fine-tuned on the basis of the numerical value to ensure that the phase of the induced electromotive force of the motor at the time of switching is consistent with the phase of the power supply voltage, the power frequency is switched when the rotational speed of the motor reaches 75% of rotational speed after power failure, the motor M is operated at the switching time of 65Hz and controlled at the time of about 200ms, the operation of the main pump motor M at the time of 50Hz and the former is controlled at the time of 150ms, the time is longer than that the amplitude of the induced electromotive force of the former and the impact current is more preferably considered in the case of switching the inertia of the switching, and the switching of the case of the switching of the power.
In the following, the detailed description will be given by taking the example of the application to the coal oil slurry feeding pump, and the performance parameters of the coal oil slurry feeding pump are first described as follows: the three-plunger reciprocating pump is used for conveying high-temperature, high-pressure and high-solid-content oil-coal slurry media, the flow rate of the pump is large, the lift is high, the load torque is large, and the performance and main parameters are as shown in a table 1:
TABLE 1 oil coal slurry feed Pump Performance parameters
The coal oil slurry feeding pump is a heavy-duty low-speed operation device, belongs to an anti-resistance constant-torque load, namely the direction of load torque is always opposite to the operation direction of the device and hinders the operation of a motor, the output torque of a main pump motor M is not related to the rotating speed and is only in direct proportion to the pressure of an outlet pipeline, the flow rate of the pump is in direct proportion to the rotating speed, the coal oil slurry feeding pump is a reciprocating pump and conveys materials in a low-pressure section into a sealed high-pressure container, and therefore the outlet pipeline has high pressure after the machine is stopped in operation. When the pump is restarted, a large load torque needs to be overcome, meanwhile, the inertial shutdown time is short, and the pump can be completely stopped within 1-2 seconds through actual measurement;
secondly, introduce the oil coal slurry charge pump and need automatic switch to power frequency operation process because of the converter trouble when normal work, because load characteristic, the motor rotational speed descends very fast after the outage, if switching time Tc selects inappropriately, the switching process produces very big impact, consequence and reason that too big impulse current caused:
the consequence is 1, when the power transformer is equipped, the reserve capacity needs to be fully considered, and great electric energy waste is brought to the power grid;
2, the excessive impact current impacts the power grid to influence the normal operation of other equipment on the same power grid, and power supply switches of other equipment may trip due to undervoltage; 3, the dynamic torque is very large in the starting process, and the mechanical impact on the production is also very large in the acceleration process of the dragging system, so that the service life of the machine is influenced.
The reason is that 1 is influenced by the decrease of the motor speed
The motor enters a free parking process after being powered off, the rotating speed of the motor is attenuated according to an exponential law, the parking time is related to the characteristics of a load and the rotary inertia of a rotor of equipment, and the values of the rotating speed of the motor, which changes along with the time after the motor is powered off, corresponding to several parking times are listed in table 2:
TABLE 2 calculated values of the rotational speed at different moments after the motor is de-energized
At the switching time, if the rotation speed of the motor has dropped a lot, the slip between the actual rotation speed and the synchronous rotation speed of the rotor is large, the dynamic torque is also large, and the speed at which the rotor winding cuts the rotating magnetic field and the induced electromotive force and the induced current generated thereby are large, so that a large impact current is generated. According to practical experience, the surge current caused by slip is within an acceptable range when the motor speed is greater than 75% of the rated speed at the switching moment.
2, influence of electromotive force induced by motor stator
After the motor is powered off, an electromagnetic transition process exists on the stator winding, and the process is represented as follows:
2.1 self-induced electromotive force of stator winding disappears immediately
After the motor is powered off, the current of the stator winding and the magnetic field of the stator winding disappear immediately, the energy of the stator winding is consumed on an electric arc between contacts at the moment when the high-voltage vacuum contactor KM2 is switched off, and the self-induction electromotive force of the stator winding disappears along with the disappearance of the magnetic field.
2.2 attenuated DC Current in the rotor winding
The rotor winding is a self-forming loop, the self-inductance electromotive force of the rotor winding prevents the current from disappearing, the current of the rotor winding has a decay process and does not alternate any more, and the initial value depends on the current value of the rotor at the moment of power failure. The decaying current produces a decaying dc magnetic field.
2.3 the electric Motor is in a synchronous Generator State
The attenuated DC magnetic field of the rotor is cut by the stator winding, and three-phase induced electromotive force is generated in the stator winding, and the magnitude of the induced electromotive force is very close to the power supply voltage at the moment of power supply disconnection.
2.4 induced electromotive force variation with time by stator winding
After the motor is powered off, the motor enters an electromagnetic transition process, and the magnitude of the induced electromotive force of the stator winding is exponentially attenuated. Although the electromagnetic transition times required for motors of different capacities vary, they are substantially on the order of magnitude. Table 3 lists the values of the induced electromotive force of the stator winding of the two electromagnetic transition time motors with time.
TABLE 3 calculated values of stator electromotive force at different moments after motor power-off
The electromagnetic transition time is generally above 2 seconds, as can be seen in table 3: if the frequency conversion cutting frequency time is more than 1 second, the effect of the induced electromotive force of the stator winding can be ignored, and if the frequency conversion cutting frequency time is less than 0.5 second, the effect can not be ignored.
For the case that the switching time is far shorter than the motor transition process time, the action of the stator winding induced electromotive force must be considered, the amplitude of the stator electromotive force after the motor is powered off becomes smaller along with the time, and the period becomes larger along with the reduction of the rotating speed.
At the switching time, if the stator electromotive force and the power supply voltage are in the same direction, no surge current flows, and otherwise, a large surge current flows. It is therefore important to capture the same directional moment of the stator emf and the supply voltage.
Finally, a speed reducer with a proper speed ratio is selected to enable the main pump motor M to be in a frequency boosting mode when the main pump motor M works under a normal working condition; the following takes the application of the coal oil slurry feed pump as an example:
m-6 level frequency conversion and frequency modulation of a main pump motor are 0-75 Hz and 50-987 rpm/min;
reducer ratio-15.389: 1;
normal pump condition-flow 24-60 m3H, outlet pressure: 20.1Mp, pump speed: 33 to 83 rpm/min.
According to the corresponding relation between the flow rate and the rotating speed of the pump and the rotating speed of the motor, calculating the time-varying frequency modulation range of the normal working condition of the pump: 25.9-65 Hz, actually measuring the output power of the motor: 158.2-397 KW.
Selecting a speed reducer with the speed ratio of 15.389:1, and when the oil-coal slurry feeding pump works at the maximum flow rate of 60m3At/h, the main pump motor M operates at 65Hz, and at the same flow rate, as compared to a retarder with a selected speed ratio of 11.891, the main pump motor M operates at 50Hz, as compared to the following two cases:
the impact current is mainly influenced by slip running with power frequency and motor induced electromotive force, the process of frequency conversion switching power frequency is that firstly the rotating speed sensor detects the rotating speed of the motor after power failure, the programmable controller P L C and the timer calculate the time value of the rotating speed of the motor after power failure dropping to over 75 percent of the limit rotating speed, then fine adjustment is carried out on the basis of the value, the phase of the motor induced electromotive force is ensured to be consistent with the phase of the power supply voltage at the switching moment,
when the rotating speed of the motor is 75% of the rated rotating speed after power failure, the power frequency is switched, the switching time of the main pump motor M when the motor runs at 65Hz needs to be controlled to be about 200ms, the time of the main pump motor M when the motor runs at 50Hz needs to be controlled to be about 150ms, the time required by the main pump motor M is longer than that required by the main pump motor M, and the amplitude of the induced electromotive force of the motor of the main pump motor M is reduced along with the extension of the time, so that the impact current of the motor is less influenced by the current of the induced electromotive force under the influence of the same slip, in addition, the main pump motor can also realize the switching at about 50Hz after the power failure, the switching effect with small slip is better, the proper switching time selection needs to be comprehensively considered by combining the actual conditions of equipment, the load inertial shutdown time and the like, so far, a control signal is output to a main circuit driving high-voltage vacuum contactor KM1 and a high-voltage vacuum contactor KM2, tc represents switching time, and when receiving the switching-on states of QF1 and KM3, the process of frequency conversion and power frequency switching is completed, and meanwhile, an alarm signal is output.
The utility model discloses when using, control system output control signal is to main circuit drive high-pressure vacuum contactor KM1, high-pressure vacuum contactor KM2 separating brake instruction, wait to receive QF1, high-pressure vacuum contactor KM2 separating brake state and time delay Tc time after the automatic output KM3 instruction of closing brake, Tc represents the switching time, when receiving QF1, KM3 closing brake state represents frequency conversion and cuts the power frequency process completion, wherein control system includes the reduction gear, make main pump motor M be in the raising frequency mode when normal operating mode work through selecting the reduction gear that the velocity ratio is suitable, still include programmable controller P L C, a speed sensor, the time-recorder, realize when main pump motor M outage back rotational speed to 75% amount rotational speed, the automatic output high-pressure vacuum contactor KM1, high-pressure vacuum contactor KM2 separating brake instruction, wait to receive high-voltage switch QF1, high-pressure vacuum contactor KM2 separating brake state and time delay Tc time after the automatic output high-pressure vacuum contactor 3 instruction of closing brake state realize frequency conversion and cut frequency conversion, Tc represents the switching time, the rotational speed limit value of the rotational speed that the rotational speed of working speed of motor M calculated by the motor M behind the outage behind the calculation is reduced to the main pump phase position.
Claims (1)
1. The frequency conversion switching power frequency device for the motor to drive the load comprises a main circuit and a control system, wherein the main circuit comprises a high-voltage switch QF1, a frequency converter cabinet VFD, an automatic power frequency bypass cabinet BY and a main pump motor M, and is characterized in that the automatic power frequency bypass cabinet BY comprises a disconnecting switch QS1, a disconnecting switch QS2, a high-voltage vacuum contactor KM1, a high-voltage vacuum contactor KM2 and a high-voltage vacuum contactor KM3, and the automatic power frequency bypass cabinet BY realizes the switching of the operation of the frequency converter to the operation of a power frequency power grid under the control of the control system;
one end of the high-voltage switch QF1 is connected with a 6KV bus, the other end of the high-voltage switch QF1 is divided into two paths, one path is connected to the left end of the frequency converter through a high-voltage vacuum contactor KM1 and a disconnecting switch QS1, the other path is connected to the left end of the automatic power frequency bypass cabinet BY, the right end of the automatic power frequency bypass cabinet BY is connected with one end of a normally open contact of a high-voltage vacuum contactor KM3, the right end of the frequency converter is connected with one end of a normally open contact of a high-voltage vacuum contactor KM2 through a disconnecting switch QS2, and the other end of the normally open contact of the high-voltage vacuum contactor KM 3;
the control system comprises a speed reducer matched with the main pump motor M, and the main pump motor M is in an up-conversion mode when working under normal working conditions by selecting the speed reducer with a proper speed ratio;
the control system comprises a programmable controller P L C, a rotating speed sensor and a timer, and is characterized in that when the rotating speed of a main pump motor M reaches 75% of limit rotating speed after power failure, switching-off instructions of a high-voltage vacuum contactor KM1 and a high-voltage vacuum contactor KM2 are automatically output, and after receiving the switching-off states of a high-voltage switch QF1 and the high-voltage vacuum contactor KM2 and delaying Tc time, a switching-on instruction of the high-voltage vacuum contactor KM3 is automatically output to realize frequency conversion and power frequency switching, wherein Tc represents switching time;
the Tc time is obtained by calculating the time value of the rotating speed of the main pump motor M which is reduced to over 75 percent of rated rotating speed after power failure, and then carrying out fine adjustment on the basis of the numerical value to ensure that the phase of the induced electromotive force of the main pump motor M is consistent with the phase of the power supply voltage at the switching moment.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112682310A (en) * | 2020-12-18 | 2021-04-20 | 江西三川节能股份有限公司 | Cement plant high temperature fan economizer system |
| CN114289168A (en) * | 2021-12-29 | 2022-04-08 | 内蒙古超牌新材料股份有限公司 | Depolymerizing machine system and starting method thereof |
| CN117072461A (en) * | 2023-10-18 | 2023-11-17 | 上海阿波罗机械股份有限公司 | Method and system for switching motors of circulating water pump of nuclear power station |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112682310A (en) * | 2020-12-18 | 2021-04-20 | 江西三川节能股份有限公司 | Cement plant high temperature fan economizer system |
| CN114289168A (en) * | 2021-12-29 | 2022-04-08 | 内蒙古超牌新材料股份有限公司 | Depolymerizing machine system and starting method thereof |
| CN114289168B (en) * | 2021-12-29 | 2023-05-09 | 内蒙古超牌新材料股份有限公司 | Method for starting depolymerizer system |
| CN117072461A (en) * | 2023-10-18 | 2023-11-17 | 上海阿波罗机械股份有限公司 | Method and system for switching motors of circulating water pump of nuclear power station |
| CN117072461B (en) * | 2023-10-18 | 2024-01-26 | 上海阿波罗机械股份有限公司 | Method and system for switching motors of circulating water pump of nuclear power station |
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Denomination of utility model: Frequency conversion switching power frequency device for motor driving load Effective date of registration: 20220927 Granted publication date: 20200804 Pledgee: Societe Generale Bank Co.,Ltd. Qingpu Branch of Shanghai Pledgor: SHANGHAI FIRST FLUID MACHINERY CO.,LTD. Registration number: Y2022980016665 |
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Date of cancellation: 20230920 Granted publication date: 20200804 Pledgee: Societe Generale Bank Co.,Ltd. Qingpu Branch of Shanghai Pledgor: SHANGHAI FIRST FLUID MACHINERY CO.,LTD. Registration number: Y2022980016665 |
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