Mining electric locomotives are crucial transportation equipment in mine operations and tunnel construction. They possess advantages such as high traction, strong overload capacity, high speed, and low maintenance costs, playing a significant role in subway construction in major cities. This article primarily introduces the successful application of the Hipumont HD30-4T250-D frequency converter in a 150-ton DC mining electric locomotive, and how frequency conversion speed regulation technology can improve locomotive control characteristics and achieve a flexible driving experience.
1. Industrial and mining electric locomotive system
The electric locomotive emerged to meet the demands of railway transportation for large carrying capacity, high speed, and greater environmental adaptability. Mining and industrial electric locomotives, using DC power, have lower power and speed compared to mainline electric locomotives. However, their flexible control and self-contained energy capabilities make them widely used for short-distance ore transportation in mines and for transporting rock debris in tunnel construction.
The DC electric locomotive for industrial and mining operations consists of a control room, a transmission system, and a battery pack. The control room controls the locomotive's operation; the transmission system is powered by two 110kW AC motors, which are driven to the wheel hubs via reducers; the brake pads are powered by a 4kW compressor; and the battery pack consists of 48 12V lead-acid batteries connected in series, providing power to the entire locomotive system.
DC mining electric locomotives have two operating conditions: when running under full load, the motor needs to operate within the 0-50Hz range, at which point the maximum operating speed is around 40 km/h, requiring sufficient torque output; when running under no-load, the motor needs to operate within the 0-70Hz range, at which point the maximum operating speed must reach 60 km/h.
The following diagram is a simplified diagram of an electric locomotive system.
2 Application Solutions
Traditional electric locomotives use chopper speed control technology, which is still used in many mines in China. However, the currently popular variable frequency speed control technology will completely revolutionize DC-powered mining electric locomotive drive technology. Variable frequency speed control offers precise control accuracy, with motor operating frequency accuracy down to 0.01Hz; it provides higher energy efficiency, saving electricity compared to conventional starting methods through soft starting; and it has a wider speed range, allowing the locomotive to operate at full load and empty speeds, with higher speeds required during empty operation, where the motor can operate within the 0-70Hz range.
2.1 System Configuration
The 150-ton DC mining locomotive uses two 110kW AC motors to power the left and right wheel hubs, while a 4kW air compressor provides the brake pressure for opening the brake pads. In our solution, we use a 250kW frequency converter to drive both main motors via a one-to-two configuration, and the 4kW frequency converter controls the air compressor via PLC commands. The application scheme for the frequency converter is shown in the following diagram:
2.2 Parameter Configuration
For applications where one inverter drives two motors simultaneously, V/f control must be used. This control method ensures that the acceleration/deceleration times and speeds of the two motors remain consistent during operation.
Main motor drive frequency converter parameter table
Parameter number | Parameter name | Setting value |
|---|---|---|
F00.10 | Frequency setting channel selection | 3 (AI Analog Value Setting) |
F00.11 | Command settings for channel selection | 1 (Terminal Operation Command Channel) |
F03.01 | Acceleration time 1 | 10S |
F03.02 | Deceleration time 1 | 10S |
F05.10 | Minimum given line 1 | 10% |
F08.00 | Motor 1 Rated Power | 250kW |
F08.02 | Motor 1 rated current | 530A |
F08.07 | Motor 1 stator resistance | 0.009Ω |
F08.08 | Motor 1 rotor resistance | 0.01Ω |
F08.09 | Motor 1 leakage inductance | 0.3mH |
F08.10 | Motor 1 mutual inductance | 4.8mH |
F08.11 | Motor 1 No-load excitation current | 12.5A |
F15.00 | DI1 terminal function selection | 2 (FWD function) |
F15.01 | DI2 terminal function selection | 3 (REV function) |
F15.02 | DI3 terminal function selection | 46 (External Reset Input) |
F15.03 | DI4 terminal function selection | 20 (Forward jog 1 command control input) |
F15.04 | DI5 terminal function selection | 21 (Reverse Jog 1 command control input) |
F15.20 | RLY1 Relay Function Selection | 09 (Frequency Level Detection Signal 1) |
F15.30 | FDT1 detection method | 1 (Detected by output frequency) |
F15.31 | FDT1 level | 5Hz |
F15.32 | FDT1 lag | 0Hz |
F16.02 | AI2 function selection for analog input | 2 (Frequency Setting Channel) |
F16.08 | Analog input AI2 bias | -8% |
F16.09 | Analog input AI2 gain | 1.4 |
F17.00 | Data format | 3 (1-7-2 format, no checksum, ASCII) |
F17.02 | Baud rate selection | 3 (9600bps) |
F23.37 | Carrier frequency setting | 2K |
1. Complete the debugging of the inverter control terminal signals.
The inverter parameter d00.50 allows for easy monitoring of whether each switch input is normal; the analog input is a 4-20mA current signal.
When debugging, allow sufficient margin for the mechanical pull rod to avoid it failing to reach the lowest or highest frequency. When debugging analog signals, adjust the bias first, then the gain.
2. Complete the terminal function parameter settings.
First, correctly set the appropriate frequency range, acceleration/deceleration control parameters, and brake relay output frequency point. Then, assign the frequency to the analog quantity. Finally, set the control command to terminal control.
3. Start system debugging
During debugging, gradually increase the output frequency, monitor the current and the balance of the three-phase output; quickly decelerate to check the bus voltage and observe whether the braking unit operates; finally, set the acceleration and deceleration time in the technical requirements, and perform operations such as forward, reverse, forward jog, reverse jog, and emergency braking.
2.4 Debugging Results
1. The locomotive operates at a maximum frequency of 70Hz, with stable speed and rapid acceleration and deceleration response.
2. Accurately output brake-holding commands when the frequency output is less than 5Hz.
3. The maximum no-load operating current is around 120A, which meets the locomotive's technical specifications.
4. The PLC output control commands to the frequency converter drive the air compressor to run well, and the entire locomotive power commissioning successfully passed the acceptance criteria.
3. Conclusion
The DC-powered electric locomotive for industrial and mining operations uses frequency conversion technology for speed regulation, and all indicators meet the locomotive's technical requirements. The advanced frequency conversion technology offers significant advantages over traditional chopper speed control in terms of energy saving and high-speed operation.
