What are the applications of frequency converters in mine hoists?

This article mainly introduces the application of Xin Kerui C500 inverter in the mine hoist of Changce Silver Mine in Yizhang County. The original system of the mine hoist of Changce Silver Mine adopts the speed regulation method of winding asynchronous motor rotor circuit series resistance. It is upgraded and transformed by C500 inverter, which greatly reduces the failure rate of the system, reduces electric energy and improves production efficiency.

1. Introduction

Mine hoist is an important equipment in the mining production process: personnel lifting, material and equipment transportation need to be completed through it. Mine hoist is called the "throat of the mine" and is the hub connecting the underground operation of the mine and the ground. As an important equipment in the mine, the reliability, safety and economic requirements of the mine hoist are all of great concern.

2. Requirements for electrical transmission of mine winches

1. Load characteristics of mine winches

When the heavy object rises, the motor needs to overcome various resistances (including the gravity and friction of the heavy object, etc.), which belongs to the resistance load. When the heavy object is lowered, since the heavy object itself has the ability to descend according to the acceleration of gravity (potential energy), therefore, when the gravity of the heavy object is greater than the friction resistance of the transmission mechanism, the gravity (potential energy) of the heavy object itself is the driving force for the descent, and the motor becomes the recipient of energy, so it belongs to the power load.

2. Requirements of the mine winch motor for the driver

① Large starting torque and good speed regulation characteristics;

② Strong overload capacity;

③ Able to output large torque at low frequency and cannot slip when suspended;

④ When lowered, the motor generates large regenerative energy, and it is required to be able to reasonably handle the motor regenerative energy.

3. Disadvantages of the traditional control system of the mine winch

① High energy consumption

The traditional speed regulation method of the mine winch is the speed regulation of the winding motor rotor series resistance. A large amount of slip power of this control system is consumed by the resistor 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 electric energy waste, which is not desirable from the perspective of energy saving and economy.

② Poor speed regulation performance

The rotor series resistance speed regulation method belongs to step speed regulation, and its speed reduction is achieved by consuming energy through the external resistance of the rotor. The most important thing is that the lower the speed, the softer the mechanical characteristics of the motor and the smaller the output torque. In addition, the step speed regulation has a great impact on the motor and mechanical equipment, the equipment runs unsteadily, the speed regulation is discontinuous, it is easy to fall off the track, and the failure rate is high. For the 24-hour continuous production mode of the mine, the economic loss is large.

③ Poor system reliability

(1) Frequent opening and closing of the contactor (frequent opening and closing of the contactor under high current conditions) often causes sintering of the contactor contacts and burning of the coil.

(2) Imperfect protection measures, prone to motor burning.

(3) The brake is subject to relatively large impact, the brake pad is severely worn, and the brake is prone to loosening, and frequent maintenance and replacement are required.

④ High maintenance cost

(1) Contactors, wound-rotor motor rotor brushes, and slip rings often require maintenance and replacement, which is costly.

(2) Reducers and brakes are subject to large impacts and often require maintenance.

(3) The characteristics of the rotor series resistance speed control method itself ultimately lead to limited production efficiency (often failures and shutdown, maintenance status), large maintenance workload, and increased maintenance costs.

4. Advantages of using C500 inverters for mine hoists

① The inverter has good speed regulation performance, large starting torque, hard mechanical characteristics, and accurate positioning.

② The inverter runs smoothly, has little impact on the reducer and brake, reduces the maintenance of the equipment, and extends the service life of the hoist.

③ After using the inverter, there is no need to use a contactor. At the same time, the wound motor can also be changed to a squirrel cage motor, and there is no need to maintain the brushes and slip rings.

④ The inverter has high operating efficiency and has perfect protection, monitoring and self-diagnosis functions for the motor and system. If combined with PLC control, it can greatly improve the reliability of the mine winch electric control system.

⑤ The internal series resistance is removed to save energy.

III. Application of C500 inverter in mine hoist

1. Overview of on-site equipment

2. According to the load characteristics and control requirements of the mine winch equipment, the main configuration of the variable frequency feedback electric control system is as follows:

3. Mine winch frequency conversion feedback energy-saving transformation system

After the mine winch system is transformed, the mine winch hoisting mechanism motor is steplessly regulated, which greatly improves the control performance of the hoisting mechanism and reduces the huge impact on the motor and mechanical parts. At the same time, energy feedback feeds the regenerated energy of the hoisting motor back to the power grid, greatly saving electricity, reducing the ambient temperature of the on-site equipment, and extending the service life of the electrical equipment. The

energy-saving transformation system has two control cabinets, which are composed of frequency converters, energy feedback devices, PLCs, contactors and other parts. Its specific functions are summarized as follows:

1. After the system transformation, the frequency conversion control mode of the hoisting motor and the original rotor series resistance power frequency control mode can be switched freely. The switching of the two control modes is electrically interlocked to ensure the safety of the system operation.

2. After the system transformation, the original operation mode and habits of the mine winch are retained, that is, the gear control and operation mode of the original cam controller are retained. In this way, it will not affect the normal operation of the mine winch operator, and ensure that the special equipment of the mine winch is qualified for inspection.

3. The frequency conversion system of the hoisting mechanism has multiple protection functions such as short circuit, overvoltage, overcurrent, phase loss, overload, overtemperature, etc., which can protect the hoisting mechanism of the mine winch to the maximum extent.

4. The system uses a frequency converter to drive the hoisting mechanism motor. When the motor drags the potential load downward, the motor will be in a regenerative power generation state, and the braking resistor consumes the excess power generated to ensure the safe operation of the system. The schematic diagram of the system principle is as follows:



4. System debugging

① PLC program and control circuit debugging.

After the equipment is installed, the control circuit is powered on, and the main circuit is not powered on. Debug the control circuit and PLC program to ensure that the control circuit and PLC logic control are correct and that all components operate normally.

② Frequency converter debugging.

a Disconnect the mine winch motor from the reducer, and the frequency converter uses V/F control mode to run at no load, and drive the motor to ensure that the motor runs stably and normally, and the frequency converter output voltage and current are normal.

B Disconnect the mine winch motor from the reducer, and the frequency converter uses PG-free vector control mode to perform rotary self-learning to obtain motor parameters. Then use the no-PG vector control mode to run the motor without load, and adjust the corresponding parameters to ensure the stable operation of the motor and the normal output voltage and current of the inverter.

c. Connect the winch motor to the reducer, use the no-PG vector control mode for the inverter, and run the inverter with load to ensure the stable operation of the motor.

d. Set some parameters of the inverter

③ Energy feedback device debugging.

Carry out no-load lowering and heavy-load lowering tests of the mine winch, correctly set the feedback action voltage value of the energy feedback device, and ensure the normal operation of the frequency converter and energy feedback system.

④ Overall debugging and operation of the system.

The entire system is tested as a whole to ensure that the mine winch is hoisted and lowered with no load and heavy load, the speed of each gear meets the requirements, the gear shift is normal, and the frequency converter and energy feedback device operate normally. And carry out the power and variable frequency switching test to ensure normal switching and normal power frequency operation.

IV. The effect and customer evaluation of the application of IPC variable frequency feedback electronic control system in the energy-saving transformation of mine winches

The actual operation of the system proves that the application of IPC variable frequency feedback electronic control system in the energy-saving transformation of mine winches does not change the original operation mode of the mine winch, and the original handbrake can basically no longer be used, which simplifies the operation.

The system operates stably and reliably, with excellent speed regulation performance, large starting torque and low-frequency torque output; when the lifting mechanism is lowered, the excess electric energy in the motor regenerative power generation state is fed back to the power grid, which greatly saves electric energy.

The customer is very satisfied with the use of IPC variable frequency feedback electronic control system in the energy-saving transformation of mine winches. After actual measurement, the IPC variable frequency feedback electronic control system can save more than 28% of electricity compared with the original mine winch winding motor rotor series resistance speed control method.

V. Conclusion

The application of C500 inverter in the energy-saving transformation of mine winches has improved the automation level of hoisting winch equipment in the mining industry and accelerated the industrial equipment upgrade of the mining industry. It has played a very positive role in improving the production capacity of the mining industry and ensuring the safe production of the mining industry.

More importantly, the mine hoisting winch equipment is a large-scale mining equipment, and its energy consumption accounts for a large proportion of the total energy consumption of the entire mine production. Compared with the winding motor rotor series resistance speed control system, the variable frequency feedback electronic control system can greatly save electricity, truly reduce the production cost of the mining industry and generate economic benefits.