From the concept of a motor, a DC motor is a DC motor that converts DC electrical energy into mechanical energy, or a DC generator that converts mechanical energy into DC electrical energy; a rotating electrical machine whose output or input is DC electrical energy is called a DC motor, which is an energy A motor that realizes the mutual conversion of DC electrical energy and mechanical energy. When it operates as a motor, it is a DC motor, which converts electrical energy into mechanical energy; when it operates as a generator, it is a DC generator, which converts mechanical energy into DC electrical energy.

For rotating motors, harmonic currents or harmonic voltages will cause additional losses in the stator windings, rotor circuits and iron cores, resulting in a reduction in the overall energy conversion efficiency of the motor. Harmonic current can increase the copper consumption of the motor, so under severe harmonic load, the motor will generate local overheating, increase vibration and noise, and increase temperature rise, resulting in accelerated aging of the insulation layer and reduced equipment life. Some fans asked, AC motors will have harmonics, whether DC motors also have this problem?

The magnitude and direction of the alternating current will change periodically with time, and the running average value in one cycle is zero, and the waveform is usually sinusoidal, while the direct current does not change periodically. Alternating current is a magnetic base, which is generated mechanically. Any alternating current must have electromagnetic properties, and there is a magnetic core material. Direct current is chemical-based, whether photovoltaic or lead-acid, mainly converts chemical energy into electrical energy.

The conversion of alternating current to direct current is through rectification and filtering to obtain pulsating direct current. The direct current is converted into alternating current through oscillation and inversion, and various sine wave alternating currents are obtained.

The main reasons for the generation of harmonics include the distortion of the fundamental current and the generation of harmonics due to the sinusoidal voltage being applied to the nonlinear load. The main nonlinear loads are UPS, switching power supply, rectifier, frequency converter, inverter, etc. The harmonics of the DC motor mainly come from the power supply. The reason for the harmonics of the AC rectifier and DC power equipment is that the rectifier equipment has a valve voltage. When it is less than the valve voltage, the current is zero.

In order to provide a stable DC power supply for this type of electrical equipment, energy storage elements such as filter capacitors and filter inductors are added to the rectifier equipment to increase the valve voltage and stimulate the generation of harmonics. In order to control the voltage and current of the DC electrical equipment, thyristor is used in the rectifier equipment, which makes the harmonic pollution of such equipment more serious, and the harmonic order is relatively low.

By Jessica