Control method for preventing variable frequency motor from burning loss
Technical Field
The invention relates to the technical field of automatic control of a slab heating furnace, in particular to a control method for preventing burning loss of a variable frequency motor, and particularly relates to a safety control method for an electric band-type brake of a heating furnace loading and tapping machine.
Background
The heating furnace charging and discharging machine is the key equipment essential to the heating furnace of the steel mill at home and abroad at present. The steel loading machines arranged on the two sides of the inlet and outlet of the heating furnace mainly support the plate blank on the roller way of the inlet furnace through the lifting arm and the translation arm and stably place the plate blank in the heating furnace, and the steel discharging machines also mainly support the plate blank heated in the heating furnace through the lifting arm and the translation arm and stably place the plate blank on the roller way of the outlet furnace.
In the action process of the heating furnace loading and tapping machine, the lifting arm and the translation arm of the heating furnace loading and tapping machine move to a certain position and braking is completed by an electric band-type brake.
A loading machine and a tapping machine of a 5m thick plate heating furnace of a certain iron and steel enterprise respectively undertake the translation and lifting actions of the loading machine and the tapping machine by two variable frequency motors, and the variable frequency motors are driven by Siemens 6SE70 series frequency converters. As shown in fig. 1, the brakes of the loading and tapping machine are all external electric band-type brake mechanisms 1, when the loading and tapping machine variable frequency motor 2 receives a starting instruction, the external electric band-type brake mechanisms 1 are opened (namely, the band-type brake pads 3 are released), and the loading and tapping machine variable frequency motor 2 drives the gear box 4 to enable the lifting arm or the translation arm to lift the slab to move to a calculation position.
When the electric band-type brake mechanism of the lifting arm is insensitive and the gap is unreasonable, the arm can freely descend due to the dead weight of the plate blank and the loading and tapping machine.
When the electric band-type brake mechanism of the translation arm is insensitive and the gap is unreasonable, the slab positioning has deviation, and the normal loading and tapping tasks cannot be completed. And a new band-type brake spare part must be replaced or the gap must be adjusted on the machine to meet normal loading and tapping.
However, in actual production, the gap of the electric band-type brake must be adjusted on the machine, and multiple times of fine adjustment are required to meet the actual production requirements. When the loading and tapping machine is normally started, an electric band-type brake command is sent to an MCC (motor control center) disc by a PLC (programmable logic controller), the MCC outputs a 24V DC power supply to the field electric band-type brake, and meanwhile, the MCC sends a state signal of opening the band-type brake to the PLC as a starting position of a control word of a translation and lifting frequency converter of the tapping machine, and meanwhile, a speed given value of the PLC is sent to the frequency converter.
When the electric band-type brake is adjusted on line, a band-type brake instruction is forced at the PLC, a control word of the frequency converter is set to be started, and the frequency converter does not receive a speed given value, so that the exciting current of the motor is greatly increased, and the motor is heated and damaged in insulation. More serious, when the clearance is adjusted after the band-type brake is replaced on line, the motor is heated and burnt out, and the production line is stopped for a long time.
When electronic band-type brake clearance of on-the-spot online adjustment, need be at converter standby state, if the repeated start, stop the converter come the cooperation experiment, adopt the mode that has a power failure to the converter although can avoid exciting current increase phenomenon, nevertheless be unfavorable for online adjustment, unusual treatment time of meeting greatly increased, consuming time power.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a control method for preventing the burning loss of the variable frequency motor, which redesigns the opening feedback signal state of the band-type brake and the starting command logic of a control word of a frequency converter, and avoids the heating and insulation damage of the motor caused by the online adjustment of the electric band-type brake.
In order to achieve the purpose, the invention adopts the following technical scheme:
a control method for preventing burning loss of a variable frequency motor comprises the following steps:
the loading and tapping machine action control process comprises the following steps:
1) the loading and tapping machine receives a starting command;
2) the variable frequency motor starts to act;
3) and the PLC judges whether the loading and tapping machine moves in place, if so, the next step of action is started, and if not, the variable frequency motor continues to act.
And starting the next action in the step 3), namely, controlling the actions of the variable frequency motor and the band-type brake of the loading and tapping machine.
The loading and tapping machine variable frequency motor and band-type brake action control process comprises the following steps:
1) the band-type brake receives a PLC action instruction;
2) if the brake action condition is met, if so, the PLC sends a brake action command to the MCC, and the step 3 is entered, and if not, the brake action is closed;
3) opening the contracting brake;
4) if the PLC receives the operation instruction of the loading and tapping machine, if so, the PLC sends a variable frequency control word to start, and the step 5 is entered, and if not, the PLC blocks the variable frequency control word to start;
5) the PLC sends a set speed to the frequency converter device;
6) outputting by a frequency converter device;
7) the variable frequency motor acts;
8) and (4) whether loading and tapping are carried out or not, calculating the position, if so, stopping the output of the frequency converter device, closing the contracting brake when the power is lost, otherwise, continuously outputting the frequency converter device, and continuously opening the contracting brake when the power is obtained.
The control method for preventing the burning loss of the variable frequency motor eliminates the control defect of equipment, avoids the accidents of heating and insulation damage of the motor caused by online adjustment of the electric brake, greatly improves the stability of the variable frequency motor, provides guarantee for the normal production of a rolling mill in the subsequent process and simultaneously reduces the maintenance cost of the equipment.
Drawings
FIG. 1 is a schematic view of the field arrangement of a band-type brake mechanism of a charging and discharging machine of a conventional heating furnace;
FIG. 2 is a flow chart of the operation control of the loader and the tapping machine in the control method of the invention.
FIG. 3 is a flow chart of control of the actions of a variable frequency motor and a band-type brake of the loading and tapping machine in the control method of the invention.
Detailed Description
The technical scheme of the invention is further explained by combining the drawings and the embodiment.
Referring to fig. 2 and fig. 3, a control method for preventing burning loss of an inverter motor according to the present invention includes:
the loading and tapping machine action control process comprises the following steps:
1) the loading and tapping machine receives a starting command;
2) the variable frequency motor starts to act;
3) and the PLC judges whether the loading and tapping machine moves in place, if so, the next step of action is started, and if not, the variable frequency motor continues to act.
Preferably, the next action in the step 3) is started, namely, the control flow of the loading and tapping machine variable frequency motor and the band-type brake action is obtained.
The loading and tapping machine variable frequency motor and band-type brake action control process comprises the following steps:
1) the band-type brake receives a PLC action instruction;
2) if the brake action condition is met, if so, the PLC sends a brake action command to an MCC (motor control center) and enters step 3, and if not, the brake action is closed;
3) opening the contracting brake;
4) if the PLC receives the operation instruction of the loading and tapping machine, if so, the PLC sends a variable frequency control word to start, and the step 5 is carried out, and if not, the PLC blocks the variable frequency control word to start;
5) the PLC sends a set speed to the frequency converter device;
6) outputting by a frequency converter device;
7) the variable frequency motor acts;
8) and (4) whether loading and tapping are carried out or not, calculating the position, if so, stopping the output of the frequency converter device, closing the contracting brake when the power is lost, otherwise, continuously outputting the frequency converter device, and continuously opening the contracting brake when the power is obtained.
In conclusion, the control method redesigns the state of the contracting brake opening feedback signal and the starting command logic of the frequency converter control word, and avoids the heating and insulation damage of the motor caused by online adjustment of the electric contracting brake. The control defect of the equipment is eliminated, the accidents of motor heating and insulation damage caused by online adjustment of the electric band-type brake are avoided, the stability of the variable frequency motor is greatly improved, the guarantee is provided for the normal production of a rolling mill in the subsequent process, and meanwhile, the maintenance cost of the equipment is also reduced.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.