Three Main Reasons for Nonlinear Error of Diesel Generator

New advances in diesel generator technology and fuel system will make diesel engine, heavy transportation, agriculture, standby power supply, and other systems desirable in recent years. Cummins, Caterpillar, and other leading diesel generator engines develop analog control systems to monitor their functions.

The simulation of diesel generator control system, the power supply of small household appliances, such as diesel generator, is a little like a small building facility. Digital control is very useful for critical equipment that requires more complex and backup power distribution systems, mixed linear and nonlinear load requirements, and uninterrupted power supply needs.

1.Working principle of DC speed measuring diesel generator: in no-load, the output voltage of DC speed measuring diesel generator is the armature induced electromotive force. Obviously, the output voltage is proportional to the speed. In addition, the output of DC speed measuring diesel generator is a pulsating voltage, and its alternating component has obvious influence on speed feedback control system and high-precision solution device.

2.Error analysis of diesel generator: it is difficult to strictly maintain the proportional relationship between the output voltage and speed of the DC speed measurement diesel generator in practice. The actual output characteristics are solid lines in the figure. The reasons for this nonlinear error are mainly the following three aspects:

(1) Armature reaction DC speed measurement When the diesel generator is loaded, the armature current will produce armature reaction, and the demagnetization effect of the armature reaction will make the air gap flux Φ Reduce 0 to reduce the output voltage. From the perspective of output characteristics, the slope will decrease, and the larger the armature current, the more significant the demagnetization effect of the armature reaction. The slope of output characteristics will decrease more significantly, and the output characteristics will become straight lines into curves.

(2) Influence of temperature If the DC speed measuring diesel genset is used for a long time, its excitation winding will heat up, and its winding resistance value will increase with the increase of temperature, so the excitation current will decrease, resulting in the decrease of air gap magnetic flux, output voltage and characteristic slope. The higher the temperature rises, the more significant the decrease in slope, causing the characteristic to bend downward. A manganese copper or constantan resistor with a large resistance value and a small temperature coefficient can be connected in series in the excitation circuit to reduce the resistance change caused by temperature changes, thereby reducing the linear error caused by temperature.

(3) If the total resistance of the armature circuit includes the contact resistance between the brush and the commutator, the output voltage is always affected by the contact resistance voltage drop and changes with the load current. When the input speed is low, the contact resistance is large, making the output voltage that is already small smaller, resulting in a large linear error; When the current is high, the contact resistance is small, and the value tends to be basically stable, the linear error is relatively much smaller.