Generator recovery of electrical load and classification of generators
I. Nature of electrical load and generator classifications:
Type of electrical load
1. Resistive load
Compared to power supplies, a load is resistive (such as ovens, etc.) when there is no phase difference between load current and load voltage. In simpler terms, a purely resistive load that operates solely through resistive components is referred to as a resistive load.
2.感性负载 - Inductive Load
Typically, loads with inductive parameters are referred to as inductive loads. Specifically, a load with a current lagging the voltage by a phase shift is considered inductive, such as transformers, motors, air compressors, drills, fans, refrigerators, air conditioners, and other similar loads. In the case of lighting fixtures, those that illuminate through gas conduction are inductive loads, including: fluorescent lights, high-pressure lights, lamps, metal halide lamps, etc.
3. Capacitive Load
A load with capacitive parameters, i.e., one that conforms to the voltage lagging current characteristic, is generally referred to as a capacitive load. During charging and discharging, the voltage cannot change abruptly. The corresponding power factor is negative, as in computers, energy-saving lamps, and LED lights.
4. Non-linear load
Non-linear loads refer to loads containing rectifying equipment. In electronic circuits, voltage and current do not maintain a linear relationship; during the connection and operation of the load, the relationship between voltage and current is often variable. Non-linearity refers to a lack of linear relationship between independent and dependent variables, which can be represented by curves or other relationships. Common typical non-linear loads include: soft starters (thyristor motor starters), switch-mode power supplies, UPS systems, inverter components, battery chargers, variable frequency controlled motors, cranes, elevators, pumps, etc., in manufacturing process control, electronic data and image equipment such as television and radio transmitting equipment, controllable lighting equipment, rectifiers, fluorescent lamps, and so on.
The impact of non-linear loads on generators: When a generator set is driven by non-linear loads and the selection does not match properly, it mainly manifests in the following types of failure phenomena:
The output voltage of the generator set suddenly increased to over 440V and became unstable.
2. The generator set's measuring instruments or controller detects an output frequency of 40~60Hz, which is unstable.
3. Generator sets exhibit severe mechanical resonance when abnormal frequencies or voltages occur, resulting in rhythmic swaying and fluctuating noises, forcing the protection devices of the diesel generator sets to activate or necessitating manual shutdown for safety.
4. High-order harmonics from non-linear loads cause abnormal conductor heating, and in severe cases, can damage the excitation circuit of the generator and the AVR.
5. Load equipment will automatically shut off the power switch due to abnormal voltage or frequency detection. If it's an UPS load, the backup battery bank will discharge to the load or supply power directly to the load from the bypass.