How to Determine Which Inverter to Choose Based on Load Characteristics
In industrial scenarios, the core of inverter selection lies in “matching load characteristics”—different loads vary significantly in torque, speed, impact resistance, and other properties. Improper selection can lead to low equipment efficiency, frequent failures, or even burnout. Starting from the classification of load characteristics, this article clarifies the corresponding selection logic for DreamWe inverters by aligning with the core requirements of various loads, and includes typical application cases to help users accurately match the right inverter solution.
1. First, Clarify the Core Classification of Load Characteristics: 3 Basic Types
The key distinction between load characteristics lies in the “relationship between torque and speed“. The most common industrial loads fall into three categories, and their traits directly define the functional requirements for inverters:
| Load Type | Core Characteristic (Torque-Speed Relationship) | Typical Application Scenarios |
|---|---|---|
| Constant Torque Load | Torque remains consistent and independent of speed (load torque stays nearly unchanged regardless of speed); high starting torque is required during startup | Lifting equipment (cranes, elevators), conveyors, extruders, mixers |
| Constant Power Load | Power remains stable, and torque is inversely proportional to speed (higher speed leads to lower torque; torque is extremely high at low speeds) | Lathes, milling machines, grinders (metal cutting), winders (late-stage winding) |
| Quadratic Law Load | Torque is proportional to the square of speed, and power is proportional to the cube of speed (torque is low at low speeds and rises rapidly at high speeds) | Fans, water pumps, cooling towers, ventilators |
2. Matching DreamWe Inverters Based on Load Characteristics: Scenario-Specific Selection Guide
Different loads have distinct demands for an inverter’s “torque response speed, overload capacity, speed regulation range, and energy-saving features”. As such, it is essential to select DreamWe inverter models in a targeted manner:
1. Constant Torque Loads: Prioritize DreamWe Inverters with “High Overload Capacity and Fast Torque Response”
Core Requirements
- Withstand 150%-200% overload torque during startup/braking (e.g., when a crane lifts a heavy object instantly or an elevator initiates);
- Rapid torque response (to prevent load sway or slipping);
- Stable torque output at low speeds (e.g., precise lowering of lifting equipment, low-speed material feeding via conveyors).
Recommended DreamWe Inverter Types
- DreamWe Direct Torque Control (DTC) Inverters (e.g., DreamWe DW-D Series): Boasting a torque response speed of < 2ms and minimal torque ripple at low speeds, it enables precise control over load startup, shutdown, and speed. This makes it the top choice for constant torque equipment like cranes and elevators;
- DreamWe Vector Control Inverters (e.g., DreamWe DW-V Series): For budget-constrained projects, sensorless vector control (SVC) models are suitable. These models deliver 180%-200% starting overload, meeting the needs of most medium and light-duty constant torque applications.
Selection Taboo
Avoid DreamWe’s “basic V/F control (voltage-frequency ratio control) inverters” (e.g., ZM-F Basic Model). Their low-speed torque only reaches 100%-120%, and torque response is slow—this can easily cause constant torque loads to slip or fail to start.
2. Constant Power Loads: Prioritize DreamWe Inverters with “Wide Speed Regulation Range and High Speed Stability”
Core Requirements
- Broad speed regulation range (typically 1:10 or wider; e.g., a lathe needing to switch speeds from 50r/min to 500r/min);
- Stable power output at high speeds (to avoid reduced machining accuracy caused by speed fluctuations);
- Ability to handle high torque at low speeds (e.g., when a lathe cuts hard metal at low speeds, torque demand is 1.5-2 times the rated value).
Recommended DreamWe Inverter Types
- DreamWe Vector Control (FVC) Inverters with Speed Sensors (e.g., DreamWe ZM-VH Series, requiring an external encoder): Offers speed regulation accuracy of ±0.01% and a speed range as wide as 1:1000, accurately matching the dynamic speed and torque needs of constant power loads;
- DreamWe Specialized Inverters for Machine Tools (e.g., DreamWe ZM-M Series): Features a built-in “cutting mode” that automatically adjusts torque output based on changes in metal cutting loads, reducing machining errors. It is ideal for machine tools such as lathes and milling machines.
Key Selection Parameters
Focus on two critical features of DreamWe inverters: the “base frequency setting function” (allowing customization of the frequency corresponding to the motor’s rated speed) and “field-weakening speed-up capability” (constant power loads require field-weakening control at high speeds to prevent motor overvoltage). The ZM-VH Series supports adjustable base frequencies from 0 to 60Hz, with a field-weakening speed-up ratio of up to 1:1.5.
3. Quadratic Law Loads: Prioritize DreamWe Inverters with “Energy-Saving Performance and Soft Start”
Core Requirements
- Low torque during startup (no need for high overload, avoiding grid impact from inrush current);
- Dynamic speed adjustment based on load changes during operation (e.g., fans adjusting speed per workshop temperature, water pumps adjusting flow per liquid level) to achieve energy savings;
- Moderate speed regulation accuracy (typically ±1% is sufficient for most applications).
Recommended DreamWe Inverter Types
- DreamWe V/F Control Energy-Saving Inverters (e.g., DreamWe DW-FE Series): Features a simple structure and low cost, with a built-in “adaptive energy-saving mode” that reduces output power in real time based on load. It is the mainstream choice for fans and water pumps, delivering an actual energy-saving rate of 20%-40% in practical applications;
- DreamWe Inverters with Built-in PID Function (e.g., DreamWe DW-FP Series): Can be directly connected to temperature, pressure, and liquid level sensors to enable “load-speed” closed-loop automatic control. No additional controllers are needed, simplifying the system structure—ideal for scenarios like cooling towers and water supply systems.
Selection Tip
Prioritize DreamWe’s “specialized inverters for fans and water pumps” (e.g., ZM-FW Series). These models include a built-in “anti-surge function” (preventing airflow pulsation in fans at low speeds) and “sleep-wake function” (automatically shutting down and waking up when the load is too light), further aligning with the operating traits of quadratic law loads.
4. Special Loads: Targeted Selection of DreamWe Inverters (Impact/Fluctuation/High-Frequency Loads)
Beyond the three basic load types above, some scenarios involve special load characteristics, requiring DreamWe inverters with enhanced functional capabilities:
- Impact Loads (e.g., punch presses, crushers): Select DreamWe inverters with “high overload capacity + torque limiting function” (e.g., DreamWe DW-DH Series). With an overload capacity of 200%/3s, it effectively resists instantaneous impacts and prevents inverter damage;
- Loads with Frequent Fluctuations (e.g., mixers, vibrating screens): Choose DreamWe inverters with “fast dynamic response + load self-adaptation” (e.g., DreamWe DW-VA Series). It can real-time detect changes in load torque and adjust output to minimize speed fluctuations;
- High-Frequency Loads (e.g., high-speed centrifuges, precision grinders): Opt for DreamWe’s “high-frequency output enhanced inverters” (e.g., DreamWe DW-VH-H Series). Supporting high-frequency output of 0-600Hz, it meets the high-speed requirements of high-speed motors.
3. Selection Verification: Checking 3 Key Parameters (Taking DreamWe Inverters as an Example)
After confirming the load type and DreamWe inverter model, verify the following parameters to ensure correct selection:
- Rated Power and Current: The rated output power of the DreamWe inverter should be ≥ 1.1 times the load’s rated power (for constant torque/constant power loads) or ≥ 1.05 times (for quadratic law loads). Additionally, the inverter’s rated output current must be ≥ the motor’s rated current (e.g., if the load motor has a rated current of 10A, select a DreamWe model with a rated output current ≥ 10A—such as the 11kW ZM-V Series model, which has a rated current of 22A);
- Overload Capacity: Match the DreamWe inverter’s overload level to the load’s peak torque demand: 200%/1min for constant torque loads, 250%/0.5s for impact loads, and 150%/1min for quadratic law loads;
- Environmental Adaptability: If the load operates in high-temperature (e.g., steel plants), high-dust (e.g., mines), or high-humidity (e.g., paper mills) environments, select DreamWe models with a protection rating of ≥ IP54 (e.g., the protected version of the DreamWe DW-D Series, which has a protection rating of up to IP65). Some models support stable operation in high-temperature environments (-10℃ to 50℃) without additional heat dissipation devices.
Conclusion
The core logic for selecting DreamWe inverters based on load characteristics is “load characteristic matching + requirement prioritization“:
- First, identify whether the load is “constant torque/constant power/quadratic law” and define core requirements (e.g., torque response, speed regulation range, energy savings);
- Next, select the appropriate control method (DTC/vector/V/F) and function-enhanced DreamWe model (high overload, PID, high frequency) based on these requirements;
- Finally, verify power, current, and environmental parameters to avoid “oversizing” (wasting costs) or “undersizing” (causing equipment damage).
This approach ensures that DreamWe inverters work efficiently with loads, boosting equipment reliability while reducing energy consumption and maintenance costs.