Abstract: This article mainly introduces the application of the special frequency converter for elevator in the mine winch. The frequency conversion electronic control system is an electrical system that upgrades the original speed regulation control method of the hoisting mechanism of mine winch featuring winding motor rotor in series with resistance. At the same time, MICNO KE300A-06 special frequency converter for elevator is used carry out frequency conversion control of the mine winch, and the energy consumption brake device is used to consume the regenerative energy generated by the mine winch in the state of regenerative power generation.
Key words: MICNO; KE300A-06 special frequency converter for elevator; Energy consumption braking device; Mine winch renovation system
The mine winch is an important link in the coal mining production process. The coal or gangue excavated from each underground working face is transported by the transportation equipment through the underground roadway to the underground car yard, and then lifted to the ground by the lifting equipment. The lifting of personnel, the transportation of materials and equipment all need to be completed by lifting equipment. It is the hub connecting the underground production system of the mine and the industrial square on the ground. "The winch is the throat of the mine" vividly describes the important role of mine hoisting.
1. Load characteristics of the mine winch
When the heavy object rises, the motor needs to overcome various resistances (including the gravity and friction of the heavy object, etc.), which is a resistance load.
When the heavy object is lowered, since the heavy object itself has the ability to descend thanks to the acceleration of gravity (potential energy), when the gravity of the heavy object is greater than the frictional resistance of the transmission mechanism, the gravity (potential energy) of the heavy object itself is the driving force for the descent. The motor becomes the receiver of energy, so it belongs to the power load.
2. The requirements of the mine winch motor for the drive
① Large starting torque and good speed regulation characteristics.
② Strong overload capacity.
③ It can output large torque at low frequency, and the winch cannot slide when suspended.
④ The motor generates a large amount of regenerative energy when it is put down, and it is required to be able to handle the regenerative energy of the motor reasonably.
3. Disadvantages of traditional control system of mine winch
① High energy consumption
The traditional speed regulation method of mine winch is winding motor rotor in series with resistance. This kind of control system consumes a large amount of slip power on the resistance connected in series with the rotor (generally it can account for more than 30% of the total energy consumption), resulting in a large amount of waste of electric energy, which is not desirable in terms of energy saving and economy.
② Poor speed regulation performance
This speed regulation method belongs to the step-by-step speed regulation, and the decrease of the speed is realized by the energy consumption of the external resistance of the rotor. The most important thing is that the lower the speed, the softer the mechanical properties of the motor and the lower the output torque. In addition, the step-by-step speed regulation has a great impact on the motor and mechanical equipment, the equipment is not running smoothly, the speed regulation is discontinuous, it is easy for the winch to fall off the road, and the failure rate is high. For the 24-hour continuous production mode of coal mines, the economic loss is large.
③ Poor system reliability
Ø The contactor is frequently opened and closed (the contactor is frequently opened and closed under the condition of high current), which often causes the sintering of the contactor and the burning of the coil.
Ø The protection measures are not perfect, and the motor is prone to burn out.
Ø The brake bears a relatively large impact, the brake skin is severely worn, and it is easy to cause the brake not to function well, and it needs to be repaired and replaced frequently.
④ High maintenance cost
Ø Contactors, winding motor rotor brushes, and slip rings often require maintenance and replacement, which cost a lot.
Ø The reducer and brake are subject to great impact and often require maintenance.
Ø The characteristics of this speed regulation method itself eventually lead to limited production efficiency (frequent failures in shutdown and maintenance status), heavy maintenance workload, and increased use and maintenance costs.
4. Advantages of frequency conversion electronic control system of mine winch
① The frequency converter has good speed regulation performance, large starting torque, hard mechanical characteristics and accurate positioning.
② The frequency converter runs smoothly and has little impact on the reducer and brake, which reduces the maintenance workload of the equipment and prolongs the service life of the elevator.
③ After using the frequency converter, there is no need to use a contactor, and the winding motor can also be changed to a squirrel-cage motor without maintenance of brushes and slip rings
④ The frequency converter has high operating efficiency, and has perfect protection, monitoring and self-diagnosis functions for the motor and system. If it is combined with PLC control, the reliability of the mine winch electric control system can be greatly improved.
(1) Overview of field equipment
A coal mine in Qitaihe has a mine winch. The winch parameters are: motor rated power is 280KW, motor rated voltage is 380V, motor rated frequency is 50Hz, motor rated speed is 966r/min, motor control mode: speed adjustment by the method of winding motor rotor in series with resistance.
(2) Configuration of the frequency converter
According to the load characteristics, rated parameters and actual operating conditions of the mine winch equipment in the field, it is determined through research and discussion that the following frequency conversion feedback electronic control system is configured for its renovated equipment, and its main parameters are as follows:
|System frequency converter||KE300A-06-350G-T4 (350KW/650A/380V)||1 unit|
|Energy braking unit||MDB-160-4 (rated current: 80A, peak current: 160A)||3 units|
|Braking resistor||5Ω, 70KW||3 units|
|DC reactor||DCL-0800-050U-0.6A (350KW-380V (AC voltage drop 6.6V)||1 unit|
3. Frequency conversion renovation system of mine winch
There are two control cabinets in the energy-saving renovation system, which are composed of frequency converter, energy braking device, PLC, contactor, etc. The specific functions are summarized as follows:
(1) After the system is renovated, the frequency conversion braking control mode of the hoist motor and the original power frequency control mode of rotor in series with resistance can be freely switched, and the two control modes are switched and electrically interlocked with each other to ensure the safety of the system.
(2) After the system is renovated, the original operation mode and habits of the mine winch are retained, that is, the original gear control and operation mode of the cam controller are retained. In this way, the normal operation of the mine winch operator is not affected, and the inspection of the special equipment of the mine winch is guaranteed.
(3) The frequency conversion braking electronic control system of the hoisting mechanism has various protection functions against short circuit, over-voltage, over-current, phase loss, overload, etc., to maximize the protection of the hoisting mechanism of the mine winch.
(4) The system adopts the frequency converter to drive the motor of the hoisting mechanism. When the motor drives the potential load down, the motor will be in the state of regenerative power generation. The energy braking device will consume the regenerative energy of the motor when the motor is in the power generation state, so as to ensure the normal operation of the frequency conversion system, and at the same time greatly save the electric energy.
The schematic diagram of the system is as follows:
Ø The control system of elevator gives the forward and reverse switching signals of the frequency converter: when the D1 terminal and the COM terminal are closed, the frequency converter will start to run forward (up); if it is disconnected, the frequency converter will be stopped; when the D2 terminal and the COM terminal are closed, the frequency converter will start to run in reverse (down), and if it is disconnected, the frequency converter will be stopped.
Ø The control system gives the switch signal to accelerate the frequency converter: when the D3 terminal and the COM terminal are closed, the frequency converter will accelerate.
Ø The frequency converter feeds back a normally open "brake output" switch signal to the control system. When the operating frequency of the frequency converter reaches the set value, the control system can release the holding brake to ensure that there is no "slip hook" phenomenon. At the same time, it is associated with the fault output of the frequency converter and outputs the normally closed signal. When a fault occurs, the brake signal can be disconnected.
4. On-site pictures
The KE300A-06 frequency converter of MICNO has achieved very good results such as high efficiency and low failure rate in the field use, and has been unanimously recognized by customers. The advantages are summarized as follows:
(1) Compared with the traditional non-speed-regulated elevator, the ride comfort is greatly improved. It ensures the comfort and safety at the moment when the brake is opened, there is no "overshoot" phenomenon in the upward movement, and there is no "weightlessness" at the moment of downward movement.
(2) Since the system adopts the low-speed braking, the relative rotating friction of the brake is small, which greatly prolongs the service life of the brake.
(3) High low frequency torque.
(4) It effectively eliminates the transmission impact of the mechanism and prolongs the service life of gears, rollers, bearings and racks. Because the frequency conversion system has the function of current limiting, the impact current to the power grid when the motor is started is reduced, and the mutual influence between the electrical equipment is alleviated.
(5) The frequency conversion speed control system has perfect safety protection functions against under-voltage, over-voltage, over-torque, over-current, etc., to ensure the reliability and safety of the entire electronic control system.
The application of MICNO KE300A-06 frequency converter in the mine winch actually solves the control problem of the mine winch very well. The automation level of the hoisting winch equipment in the coal mining industry has been improved, and the upgrading of industrial equipment in the coal mining industry has been accelerated. And the use of frequency converter control makes the system control simpler. The control system has multiple protections, which ensures the comfort and safety at the moment when the brake is opened. There is no "overshoot" phenomenon in the upward movement, and there is no "weightlessness" at the moment of downward movement. The system is more secure and reliable.