Advantages of DTC Technology in Lifting Equipment
DTC (Direct Torque Control) technology, as an advanced inverter control method, enables the direct and precise regulation of motor torque and flux. It effectively addresses the pain points of traditional control technologies—such as slow response speeds, poor stability, and low energy efficiency—when applied to lifting equipment. Its core advantages can be elaborated from five key dimensions: operational efficiency, control precision, adaptability to working conditions, system maintenance, and economic benefits, as detailed below:
1. Operational Efficiency: Fast and Accurate Torque Response to Reduce Idle Waiting
The core requirement of lifting equipment is frequent start-stops and rapid load changes (e.g., lifting/lowering heavy objects, adjusting operating positions), which demands an extremely high dynamic torque response speed.
DTC technology eliminates the need for complex coordinate transformations (such as the rotational transformation used in traditional vector control) and the simplification of motor mathematical models. Instead, it calculates and controls electromagnetic torque directly in the stator coordinate system, achieving a dynamic response speed of < 2ms—far faster than the tens of milliseconds required by traditional control systems.
DTC technology eliminates the need for complex coordinate transformations (such as the rotational transformation used in traditional vector control) and the simplification of motor mathematical models. Instead, it calculates and controls electromagnetic torque directly in the stator coordinate system, achieving a dynamic response speed of < 2ms—far faster than the tens of milliseconds required by traditional control systems.
- Practical Scenario: When lifting steel bars or cement at construction sites, DTC technology allows cranes to respond instantly to “lifting” commands. It quickly increases torque to meet load requirements, avoiding the waiting time caused by the “slow start” of traditional systems. Compared with traditional control methods, operational efficiency can be improved by approximately 30%, making DTC particularly suitable for high-frequency, fast-paced lifting operations.
2. Control Precision: Precise Speed and Position Regulation to Ensure Operational Safety
In precision lifting scenarios (e.g., transporting high-value equipment, fragile components, or installing precision instruments), “zero sway and high-precision positioning” are critical.
DTC technology uses stator flux orientation and directly adjusts stator flux and electromagnetic torque via a two-position “bang-bang controller,” enabling:
DTC technology uses stator flux orientation and directly adjusts stator flux and electromagnetic torque via a two-position “bang-bang controller,” enabling:
- Precise Low-Speed Control: Even when heavy objects move at an extremely low speed of 0.1 r/min, sway caused by torque ripple can be avoided;
- Millimeter-Level Positioning: For example, when lifting engines in automobile factories, positioning errors can be controlled within ±1 mm. This ensures engines are accurately aligned with installation stations, reducing defect rates caused by positioning deviations.
3. Adaptability to Working Conditions: Strong Low-Speed Performance and Robustness for Complex Environments
Lifting equipment often operates under complex conditions, including low-speed heavy loads, harsh environments (high temperatures, dust, humidity), and sudden load changes (e.g., spreaders suddenly hooking heavy objects, wind load interference). The adaptability advantages of DTC technology are particularly notable:
- High Torque Output at Low Speeds: Traditional control systems tend to suffer from “insufficient torque” or “speed fluctuations” at low speeds. However, by precisely controlling stator flux, DTC maintains an output of over 95% of the rated torque even in the low-speed range (below 5 Hz), with a torque ripple rate of less than 3% (traditional control typically exceeds 8%). For instance, during container loading and unloading at ports, DTC enables “slow lowering and precise alignment,” preventing cargo collisions.
- Strong Robustness (Anti-Interference Capability): DTC uses stator flux as the controlled variable, and its calculation model is not affected by changes in rotor parameters (e.g., rotor resistance, inductance). Even amid grid voltage fluctuations (within ±15%), high temperatures (e.g., in hot-rolling workshops of steel plants), or dusty environments (e.g., mine cranes), the system operates stably. This reduces the failure rate by approximately 40% compared with traditional control systems.
4. System Maintenance: Simplified Structure to Cut Costs and Ease Debugging
Traditional vector control requires complex current decomposition, rotational transformation, and PI current controllers, resulting in cumbersome system structures and high debugging difficulty. In contrast, DTC technology simplifies the system through the following designs:
- It eliminates the “rotational transformation” and “current closed-loop control” links, directly generating SVPWM (Space Vector Pulse Width Modulation) waveforms using torque and flux control signals;
- The controller’s hardware structure is more compact, reducing the number of sensors and the computational burden of complex algorithms.
This not only lowers equipment manufacturing costs by approximately 10%-15% but also simplifies debugging. Technicians do not need to perform complex parameter tuning (e.g., rotor parameter identification), shortening debugging time by more than 50%. Additionally, it reduces the complexity of later maintenance and the time required for fault diagnosis.
5. Economic Benefits: High Energy Efficiency to Reduce Long-Term Operating Costs
Lifting equipment is a high-energy-consumption device, especially under conditions with frequent start-stops and large load fluctuations. The on-demand energy supply feature of DTC technology significantly reduces energy consumption:
- Principle: It adjusts the motor’s torque and speed in real time based on the load, avoiding energy waste from the “big horse pulling a small cart” phenomenon in traditional systems (e.g., maintaining high speeds and high currents even under light loads);
- Practical Effect: Field tests in ports, steel plants, and other scenarios show that lifting equipment using DTC technology reduces energy consumption by 15%-25% compared with traditional equipment. For example, a 160 kW bridge crane operating 8 hours a day (with an electricity cost of 0.8 CNY per kWh) can save approximately 71,700 CNY in annual electricity bills (calculation: 160×8×365×0.2×0.8), delivering significant long-term economic benefits.
Conclusion
With its core advantages—fast response, high precision, strong adaptability, easy maintenance, and high energy efficiency—DTC technology perfectly meets the core needs of lifting equipment: safety, efficiency, and economy. Currently, it is widely used in various types of lifting equipment, including bridge cranes, tower cranes, port gantry cranes, and mine hoists. As inverter technology advances, DTC can also integrate with the Internet of Things (IoT) and intelligent diagnosis systems to further enable intelligent operation and maintenance of lifting equipment, offering broad application prospects.