Method and device for effectively reducing electric energy consumption in bar continuous rolling
By adjusting the excitation current mode in the continuous rolling production of bars and detecting the mill status with a programmable controller and inverter, the problem of power waste during the rolling mill is solved, and the reduction of power consumption and economic benefits are achieved.
Patent Information
- Application Number
- CN202510504522.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-22
- Publication Date
- 2025-08-15
AI Technical Summary
In the existing continuous rolling production of bars, the main motor of the rolling mill still maintains the rated excitation current when it is no load, resulting in unnecessary power loss and increasing production costs.
The excitation current mode of the bar continuous rolling mill is adjusted to a low when no load, and the rolling parts are restored to the rated value before rolling into the mill. The rolling mill state is detected in real time through a programmable controller and inverter to realize dynamic adjustment of the excitation current and reduce the no-load power consumption.
Without affecting the dynamic adjustment performance of the rolling mill, the power loss under no load is significantly reduced and economic benefits are improved.
Smart Images
Figure CN120498328A_ABST
Abstract
Description
Technical Field
[0001] This patent application belongs to the field of automatic control technology for metallurgical equipment, and more specifically, relates to a method for effectively reducing power consumption in continuous rolling of bars. Background Art
[0002] In existing continuous bar rolling production, the excitation current of the rolling mill's main motor is always maintained at its rated value, regardless of whether the mill is loaded or unloaded. However, when the mill is unloaded, its no-load torque is very low. The air gap flux generated by the low stator excitation current is sufficient to ensure that the stator and rotor of the rolling mill's main motor do not lose step (consistent speed). If the rated excitation current is still high when the mill is unloaded, it will cause unnecessary energy loss and inevitably increase the company's production costs. The rolling mill's operating power consumption accounts for the largest proportion of the entire production line. Therefore, reducing the mill's power consumption during the no-load period can significantly reduce the power consumption per ton of steel produced, with significant economic benefits. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a method and device for effectively reducing the power consumption in continuous rolling of bars. The method changes the traditional working mode in which the excitation current of the main motor of the continuous rolling mill of bars is always maintained at the rated value to a working mode in which a lower excitation current is maintained when the mill is no-loaded, and the excitation current of the main motor is restored to the rated value before the rolled piece is rolled into the rolling mill. This method can effectively reduce the power loss in the no-load state without affecting the dynamic adjustment performance of the rolling mill, thereby achieving the purpose of reducing costs and increasing efficiency.
[0004] In order to solve the above problems, the technical solution adopted by the present invention is: A method for effectively reducing power consumption in continuous bar rolling includes two aspects: grouping rolling mills and single rolling mills (rolling mills are not grouped). The working process is as follows: When the rolling mill is automatically started in groups, the excitation current of the rolling mill is controlled to be the rated value, and after the start-up, the excitation current of the rolling mill is converted to a small no-load excitation current; when the hot rolled pieces arrive upstream of the controlled rolling mill (detected by the hot metal detector or the load signal of the upstream rolling mill), the excitation current of the main motor of the controlled rolling mill is delayed and controlled to increase from the no-load excitation current to the rated excitation current; the motor maintains the rated excitation current during the loading process of the rolling mill; after the rolled pieces leave the rolling mill, the excitation current of the main motor of the rolling mill is converted from the rated value to the no-load excitation current; when the rolling mill stops, in order to ensure sufficient electromagnetic braking torque, the excitation current of the main motor of the rolling mill is immediately converted to the rated value.
[0005] When the rolling mills are not grouped, the excitation current is not converted when a single rolling mill is started, operated, or stopped, and the excitation current always remains at the rated value.
[0006] Judgment of no-load and loaded status of rolling mill The output electromagnetic torque values of the main motor of the rolling mill under no-load and loaded conditions are significantly different. The working status of the rolling mill can be accurately judged based on the amplitude change of the real-time electromagnetic torque.
[0007] Figure 2 As shown, the programmable controller detects the electromagnetic torque of the main motor of the controlled rolling mill in real time. When the real-time electromagnetic torque is greater than the load characteristic value, it is judged that the rolling mill is in a loaded state; when the real-time electromagnetic torque is less than the load characteristic value, it is judged to be in an unloaded state.
[0008] 2. Excitation current conversion of rolling mill main motor The rolling mill has four operating states: start-up, no-load operation, loaded operation, and stop. The corresponding transition processes are: transition from stop state to start state, transition from start-up completion to no-load state, transition from no-load to loaded state, transition from loaded to no-load state, and transition during stop.
[0009] The transition from the stop state to the start state begins when the programmable controller issues the rolling mill start command, and the excitation current of the rolling mill main motor maintains the rated excitation value to ensure sufficient starting torque.
[0010] The rolling mill starts and switches to the no-load state. When the programmable controller detects that the rolling mill speed reaches the given speed value, it determines that the starting process is completed and the main motor excitation current is immediately converted to the no-load excitation current.
[0011] The conversion from no-load to loaded state, the trigger signal for the conversion from no-load excitation current to rated excitation current during normal production is the upstream reliable signal of the rolling mill (such as upstream thermal inspection or upstream rolling mill loaded signal). Figure 2 In the process, the programmable controller receives the upstream trigger signal ( Figure 2 After point a), delay T2 ( Figure 2 Point c) controls the rated excitation current output of the inverter of the rolling mill. Since the excitation current has a certain adjustment time (T3) from low excitation to rated excitation, the selection of the upstream trigger signal should ensure the crossing time T1 (from the trigger signal to the controlled rolling mill load) Figure 2 (a to b) is greater than the sum of the adjustment time T3 for converting the no-load excitation current to the rated excitation current and the conversion margin time T4. Otherwise, the trigger signal at the upstream front end should be selected. T2 meets the following conditions: T2≤T1-(T3+T4) Where: The workpiece transit time T1 is equal to the distance from the trigger signal to the center of the controlled mill roll divided by the rolling speed of the upstream mill. The adjustment time T3, from no-load excitation current to rated excitation current, is related to the dynamic performance of the transmission system and is generally less than 1 second. T4 is related to the difference between the upstream mill speed and the actual workpiece speed and is generally 2-3 seconds.
[0012] Conversion from loaded to no-load state: When the rolling mill changes from loaded to no-load state (point d in the figure) and there is no upstream trigger signal, the programmable controller controls the inverter to output a low no-load excitation current.
[0013] The excitation current conversion during parking: from the moment the programmable controller issues a stop command, the main motor excitation current immediately resumes the rated excitation current to ensure that sufficient braking torque is provided. After the rolling mill speed is zero, the inverter output pulse is blocked and the current output is zero.
[0014] 3. No-load excitation current selection When the rolling mill is idling, the excitation current value of the main motor should meet the no-load torque requirements of the rolling mill at this time.
[0015] In addition, the present invention also discloses a device for effectively reducing power consumption in continuous rolling of bars, including a programmable controller, an inverter, a main motor of a controlled rolling mill, and a communication network. The programmable controller and the inverter are connected through the communication network, the inverter is electrically connected to the main motor, and the inverter drives the main motor to provide power for the rolling mill.
[0016] Due to the adoption of the above technical solution, the beneficial effects achieved by the present invention are: This method changes the traditional working mode in which the excitation current of the main motor of the bar rolling mill is always kept at the rated value to a working mode in which a lower excitation current is maintained when the rolling mill is no-loaded, and the excitation current of the main motor is restored to the rated value before the rolled piece is rolled into the rolling mill. This method can effectively reduce the power loss in the no-load state without affecting the dynamic adjustment performance of the rolling mill, thereby achieving the purpose of reducing costs and increasing efficiency.
[0017] This method only reduces the excitation current of the main motor when the rolling mill is idling, does not affect the dynamic adjustment performance during normal rolling, can significantly reduce power consumption, has significant economic benefits, and has extremely high promotion and application value in the industry. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of the composition of the electrical device of the present invention.
[0019] Figure 2 It is a control process curve diagram of the present invention.
[0020] The following are marked in the figure: Programmable controller 1, inverter 2, rolling mill main motor 3, communication network 4.
[0021] Upstream rolling mill torque and current curve 5, controlled rolling mill torque and current curve 6, upstream rolling mill in loaded state 7, controlled rolling mill in loaded state 8, upstream rolling mill loaded start signal a, controlled rolling mill excitation current conversion delay trigger signal c, controlled rolling mill loaded start signal b, controlled rolling mill loaded end signal d, the time T1 for the rolled piece to pass from the trigger signal of the upstream rolling mill to the controlled rolling mill, the delay time T2 for the excitation current conversion of the controlled rolling mill, the adjustment time T3 for the conversion of the no-load excitation current to the rated excitation current, and the conversion margin time T4. DETAILED DESCRIPTION
[0022] The present invention is further described in detail below with reference to the embodiments.
[0023] A method for effectively reducing power consumption in continuous bar rolling, such as Figure 2 , including the case of rolling mill groups and single rolling mill, When the rolling mills are grouped: when the rolling mills are automatically started in groups, the controlled rolling mills are in the transition from the stop state to the start state, and the excitation current of the main motor of the controlled rolling mill is the rated excitation current; after the start is completed, the controlled rolling mills are in the transition from the start completion state to the no-load state, and the excitation current of the controlled rolling mills is converted to a small no-load excitation current; when the hot-rolled pieces arrive from the upstream of the controlled rolling mills, the controlled rolling mills are in the transition from the no-load state to the loaded state, and the excitation current of the main motor of the controlled rolling mills is increased from the no-load excitation current to the rated excitation current by delay control; the motor of the controlled rolling mills maintains the rated excitation current during the loading process; after the rolled pieces leave the rolling mills, the controlled rolling mills are in the transition from the loaded state to the no-load state, and the main motor of the controlled rolling mills is converted from the rated excitation current to the no-load excitation current; when the rolling mills stop, in order to ensure sufficient electromagnetic braking torque, the excitation current of the main motor of the controlled rolling mills is immediately converted to the rated excitation current; When a single rolling mill is started, operated or stopped, the excitation current is not converted and the excitation current always maintains the rated value.
[0024] The no-load and loaded states of the rolling mill are judged by the amplitude change of the real-time electromagnetic torque of the main motor of the controlled rolling mill. When the real-time electromagnetic torque is greater than the load characteristic value, the rolling mill is judged to be in the loaded state; when the real-time electromagnetic torque is less than the load characteristic value, the rolling mill is judged to be in the no-load state.
[0025] In the no-load state, the electromagnetic torque is 2%-5% of the rated electromagnetic torque; in the loaded state, the electromagnetic torque is more than 18% of the rated electromagnetic torque, and the load characteristic value is 10% of the rated electromagnetic torque.
[0026] The arrival of hot rolled pieces upstream of the controlled rolling mill is detected and judged by the hot metal detector or the trigger signal carried by the upstream rolling mill.
[0027] When the controlled rolling mill is in the transition from no-load to loaded state, The delay time of the excitation current conversion of the controlled rolling mill is recorded as T2. When the upstream trigger signal ( Figure 2 After the upstream and middle mills start to load the signal (point a), the delay is T2 ( Figure 2 The excitation current conversion delay trigger signal of the controlled rolling mill (point c) controls the rolling mill to output the rated excitation current. The adjustment time of converting the no-load excitation current of the controlled rolling mill to the rated excitation current is recorded as T3 (abbreviated as the excitation current conversion time), the conversion margin time is recorded as T4, and the time for the rolled piece to pass from the trigger signal of the upstream rolling mill to the controlled rolling mill is recorded as T1. Therefore, the selection of the upstream trigger signal should ensure the passing time T1 ( Figure 2 The time from the load start signal a of the upstream mill to the load start signal b of the controlled mill is greater than the sum of the adjustment time T3 for converting the no-load excitation current to the rated excitation current and the conversion margin time T4, that is, T1>T3+T4. Otherwise, the trigger signal at the front end of the upstream should be selected, and T2 meets the following conditions: T2≤T1-(T3+T4).
[0028] The time T1 for the rolled piece to pass from the trigger signal of the upstream rolling mill to the controlled rolling mill is equal to the distance between the trigger signal and the center of the roller of the controlled rolling mill divided by the rolling speed of the upstream rolling mill; the adjustment time T3 for converting the no-load excitation current to the rated excitation current is related to the dynamic performance of the transmission system, and is generally within 1 second; the conversion margin time T4 is related to the difference between the rolling speed of the upstream rolling mill and the actual speed of the rolled piece, and can generally be 2-3 seconds.
[0029] The present invention also discloses a device for effectively reducing power consumption in continuous bar rolling, which is described by taking a Siemens S7-1500 programmable controller 1, an S120 inverter 2, and a main motor 3 of a continuous bar roughing mill group (1# rolling mill, 2# rolling mill) as an example.
[0030] like Figure 1 As shown in FIG, the programmable controller 1 is connected to the inverter 2 via a communication network 4, the inverter 2 is electrically connected to the main motor 3, and the inverter 2 drives the main motor 3 to provide power for the rolling mill.
[0031] The specific method involves the programmable controller S7-1500 determining the no-load and loaded states of the roughing mill. When the mill is no-load, it controls the S120 inverter to output a low excitation current to the main motor. Before the mill is loaded, the excitation current is increased to the rated excitation current. This significantly reduces energy loss in the no-load state while ensuring normal rolling. The programmable controller S7-1500 adjusts the main motor's excitation current by changing the transmission parameters of the S120 inverter.
[0032] 1. Judgment of no-load and loaded status of rolling mill The electromagnetic torque output by inverter 2 differs significantly between the no-load and loaded states of the rolling mill. Programmable controller 1 (S7-1500) determines the mill's operating status based on the amplitude of the electromagnetic torque jumps output by inverter 2: the no-load electromagnetic torque of the roughing mill is 2%-5% of the rated torque, while the loaded torque is above 18%. Programmable controller 1 uses 10% of the rated electromagnetic torque as the load characteristic value. When the electromagnetic torque exceeds this value, the mill is considered loaded; when the electromagnetic torque is below this value, the mill is considered no-load.
[0033] 2. Excitation current conversion The transition from the stop state to the start state, once the programmable controller 1 issues a rough rolling group start command, S120 controls the excitation current of the rolling mill main motor 3 to maintain the rated value.
[0034] When the startup is completed and the state is converted to no-load state, S7-1500 detects in real time that the speed of the main motor has risen to the given speed value, and determines that the startup of the rolling mill is completed, and immediately controls the inverter 2 to reduce the excitation current of the main motor 3 of the rolling mill to the no-load excitation current.
[0035] Combine Figure 2 , the conversion from no-load to loaded state, the ratio of the distance between the first and second rough rolling mills to the rolling speed of the first mill is the rolling piece crossing time T1, which is longer than the adjustment time T3 of the second mill excitation current from low to high (about 1 second). In order to save energy to the greatest extent, the holding time of the no-load excitation current should be extended as much as possible. Therefore, when the first mill is loaded ( Figure 2 Point a) Delay T2 ( Figure 2 At point c), S7-1500 controls the rolling mill inverter to output rated excitation current to the second main motor. After T3+T4 time (T3 can be 1 second, T4 can be 2 seconds), the second rolling mill starts to carry load ( Figure 2 The controlled rolling mill has a load starting signal (point b).
[0036] During the transition from loaded to no-load state, the torque of the second rolling mill is reduced to below the loaded characteristic value ( Figure 2 At point d, the load end signal of the controlled rolling mill is output, and S7-1500 controls inverter 2 to output no-load excitation current for the second main motor.
[0037] Figure 2 The area between point b and point d shows the two states of the upstream mill being in the loaded state 7 and the controlled mill being in the loaded state 8. The torque current curve 5 of the upstream mill and the torque current curve 6 of the controlled mill can be seen from the curve. Figure 2 It can be seen in.
[0038] Conversion during parking: When S7-1500 issues a stop command, it controls inverter 2 to output rated excitation current for the second main motor. When the speed of the second rolling mill drops to zero, inverter 2 blocks the output pulse, the current is zero, and the rolling mill stops.
[0039] During signal conversion, the S7-1500 programmable controller 1 modifies the value of P1580 in the S120 parameter via asynchronous communication to change the excitation current supplied to the main motor by inverter 2. To prevent motor noise and excessive current fluctuations caused by sudden changes in excitation current, the smoothing parameter P1582 in the S120 excitation current setting should be modified. A recommended setting is 100-200 milliseconds.
[0040] When a single rolling mill is started, operated or stopped, the excitation current is not converted and the excitation current always remains at the rated value.
[0041] 3. No-load excitation current selection When the mill is unloaded, the main motor's excitation current must meet the mill's no-load torque requirements. The no-load torque of a roughing mill is approximately 2%-3% of the rated torque. An excitation current equal to 50% of the rated value (the lower limit of the S120 inverter parameter P1580) can meet the mill's no-load drive requirements. Therefore, when the S120's P1580 parameter is unloaded, set it to 100% (corresponding to 50% of the main motor's rated excitation current) and when loaded, set it to 0 (corresponding to 100% of the main motor's rated excitation current).
Claims
1. A method for effectively reducing power consumption in continuous bar rolling, characterized in that: The process is: When the rolling mills are automatically started in groups, the controlled rolling mills are in the transition from the stopped state to the started state, and the excitation current of the main motor of the controlled rolling mills is the rated excitation current; After the start-up is completed, the controlled rolling mill is in the transition from the start-up completion state to the no-load state, and the excitation current of the controlled rolling mill is converted into the no-load excitation current; When the hot rolled pieces from the upstream of the controlled rolling mill arrive, the controlled rolling mill is in the transition from no-load to loaded state, and the excitation current of the main motor of the controlled rolling mill is increased from the no-load excitation current to the rated excitation current by delay control; The motor of the controlled rolling mill maintains the rated excitation current during the loaded state; after the rolled piece leaves the rolling mill, the controlled rolling mill is in the transition from loaded to no-load state, and the main motor of the controlled rolling mill is converted from the rated excitation current to the no-load excitation current; when the rolling mill stops, in order to ensure sufficient electromagnetic braking torque, the excitation current of the main motor of the controlled rolling mill is immediately converted to the rated excitation current; When a single rolling mill is started, operated, or stopped, the excitation current is not converted and the excitation current always remains at the rated value.
2. The method for effectively reducing power consumption by continuous bar rolling according to claim 1, characterized in that: The no-load and loaded states of the rolling mill are judged by the amplitude change of the real-time electromagnetic torque of the main motor of the controlled rolling mill. When the real-time electromagnetic torque is greater than the load characteristic value, the rolling mill is judged to be in the loaded state; when the real-time electromagnetic torque is less than the load characteristic value, the rolling mill is judged to be in the no-load state.
3. The method for effectively reducing power consumption by continuous bar rolling according to claim 2, characterized in that: The load characteristic value is 10% of the rated electromagnetic torque.
4. The method for effectively reducing power consumption by continuous bar rolling according to claim 1, characterized in that: The arrival of hot rolled pieces upstream of the controlled rolling mill is detected and judged by the hot metal detector or the trigger signal carried by the upstream rolling mill.
5. The method for effectively reducing power consumption in continuous bar rolling according to claim 1, characterized in that: When the controlled rolling mill is in the transition from no-load to loaded state, The delay time of the controlled rolling mill excitation current conversion is recorded as T2. After receiving the upstream trigger signal, the delay T2 controls the rolling mill to output the rated excitation current. The adjustment time for converting the no-load excitation current to the rated excitation current is recorded as T3, and the conversion margin time is recorded as T4. The time for the rolled piece to pass from the trigger signal of the upstream rolling mill to the controlled rolling mill is recorded as T1. T1>T3+T4, otherwise the trigger signal from the upstream front end is selected. T2 meets the following conditions: T2≤T1-(T3+T4).
6. The method for effectively reducing power consumption by continuous bar rolling according to claim 5, characterized in that: The adjustment time T3 for converting the no-load excitation current to the rated excitation current is within 1 second; the conversion margin time T4 is 2-3 seconds.
7. A device for effectively reducing power consumption in continuous bar rolling, used to implement the method according to any one of claims 1 to 6, characterized in that: It includes a programmable controller, an inverter, a main motor of the controlled rolling mill, and a communication network. The programmable controller and the inverter are connected through the communication network, the inverter is electrically connected to the main motor, and the inverter drives the main motor to provide power for the rolling mill.
8. The device for effectively reducing power consumption in continuous bar rolling according to claim 7, characterized in that: The programmable controller model is S7-1500 and the inverter model is S120 inverter.