What are the characteristics of inverter motors

The characteristics of inverter motors are as follows:

1. Electromagnetic design.

Compared with ordinary asynchronous motors, the main performance parameters considered in the design of variable frequency motors are overload capacity, starting performance, efficiency and power factor. Whereas, for variable frequency motors, the critical slip rate is inversely proportional to the power supply frequency. It can be started directly when the critical slip rate is close to 1.

As a result, overload capacity and start-up performance no longer need to be thought about too much. However, the key question to be solved is how to improve the adaptability of the motor to non-sine wave power supplies.

The approach is generally as follows:

Minimize stator and rotor resistance. Reducing the stator resistance reduces the fundamental copper loss to compensate for the increase in copper loss caused by higher harmonics.

In order to suppress the higher harmonics in the current, it is necessary to increase the inductance of the motor appropriately. However, the rotor groove leakage resistance is larger, and the skin effect is also larger, and the copper loss of higher harmonics is also increased. Therefore, the size of the motor leakage impedance should take into account the rationality of impedance matching in the whole speed control range.

The main magnetic circuit of the variable frequency motor is generally designed to be unsaturated, one is to consider the higher harmonics will deepen the saturation of the magnetic circuit, and the other is to consider that the output voltage of the inverter is appropriately increased in order to increase the output torque at low frequency.

2. Structural design.

In the structural design, the influence of non-sinusoidal power supply characteristics on the insulation structure, vibration, noise cooling mode and other aspects of the variable frequency motor is mainly considered, and the following issues are generally paid attention to:

The insulation grade, generally F or higher, strengthens the insulation strength of ground insulation and wire turns, especially considering the ability of insulation to withstand impulse voltage.

For the vibration and noise problems of the motor, it is necessary to fully consider the rigidity of the motor mechanism and the whole, and try to increase its natural frequency as much as possible to avoid the phenomenon of vibration with each force wave.

Cooling method: Forced ventilation cooling is generally adopted, that is, the main motor cooling fan is driven by an independent motor.

To prevent shaft current, bearing insulation measures should be used for motors with a capacity of more than 160kw. When the current generated by other high-frequency components is combined, the shaft current will increase greatly, resulting in bearing damage, so insulation measures should generally be taken.

For the constant power variable frequency motor, when the speed exceeds 3000 min, a special grease with high temperature resistance should be used to compensate for the temperature increase of the bearing.

1. The function of the inverter is to realize the variable speed operation of the motor and adjust the power of the motor, so as to achieve power saving; 2. The function of the inverter can also reduce the voltage fluctuation of the power line.

The energy saving of the inverter is mainly manifested in the application of fans and pumps. In order to ensure the reliability of production, all kinds of production machinery are designed with power drive, and there is a certain amount of surplus. When the motor cannot run at full load, in addition to meeting the requirements of power drive, the excess torque increases the consumption of active power, resulting in a waste of electric energy.

The traditional speed regulation method of fans, pumps and other equipment is to adjust the air supply volume and water supply by adjusting the baffle plate and valve opening of the inlet or outlet, and its input power is large, and a large amount of energy is consumed in the interception process of the baffle and valve. When using inverter speed regulation, if the flow requirement is reduced, the speed of the pump or fan can be reduced to meet the requirements.

There are three main points of energy saving:

The first inverter has a filter capacitor inside, and its storage function can improve the power factor. Second.

The inverter start is a smooth start, avoiding other high-current starts. Third, the inverter can control the speed of the motor, when your motor does not need to rotate so fast, the inverter controls the motor to run the corresponding speed, if your motor can not meet the requirements under the power frequency full 50hz operation, the speed regulation function of the inverter will fail. The third one is not much to save electricity.

Instead, the power consumption of the inverter itself is wasted.

The speed of the motor n

60f/p(1-s)

n: The speed of the motor.

f: Power frequency.

p: The number of pole pairs of the motor.

s: slip rate of the motor.

The rotation speed of the motor is proportional to the frequency, so changing the frequency can change the rotation speed of the motor in proportion. The function of the motor using the inverter is to regulate the speed and reduce the starting current.

In order to generate variable voltages and frequencies, the device first converts the alternating current of the power supply into direct current (DC), a process called rectification. A device that converts direct current (DC) into alternating current (AC) is scientifically called an "inverter". Generally, the inverter is an inverter power supply that converts the DC power supply into an inverter power supply with a certain fixed frequency and a certain voltage.

For inverters with adjustable frequency and voltage, we call them inverters. The waveform output by the inverter is an analog sine wave, which is mainly used for speed regulation of three-phase asynchronous motors, also known as frequency conversion governors. For variable frequency inverters with high waveform requirements mainly used in instrumentation testing equipment, the waveform should be sorted out, and a standard sine wave can be output, which is called variable frequency power supply.

The general inverter power supply is 15 20 times that of the inverter. Since the main device that produces the variable voltage or frequency in the inverter equipment is called "inverter", the product itself is named "inverter", that is: inverter.

The inverter technology is very mature, just choose one.

The functions of the inverter on the motor are as follows:

The inverter integrates high-voltage and high-power transistor technology and electronic control technology, and is widely used. The function of the inverter is to change the frequency and amplitude of the AC motor power supply, so as to change the period of its moving magnetic field, so as to achieve the purpose of smoothly controlling the speed of the motor. The emergence of the inverter has simplified the complex speed control, and the combination of inverter + AC squirrel cage induction motor has replaced most of the work that can only be completed by the DC motor, reducing the volume, reducing the maintenance rate, and making the transmission technology develop to a new stage.

1. When starting, the starting current can be reduced (compared with starting the motor directly without an inverter), 2. Long-term operation is more energy-saving than that without inverter, 3. Stepless speed regulation can be carried out, vector control, V F control, etc. 4. Using the communication function of the inverter, the upper function can monitor the operation of the motor in real time (such as current, speed, etc.).

The mechanical parts with high balance quality and vibration level R (vibration reduction level) have high machining accuracy, and special high-precision bearings are used to enable high-speed operation.

The forced ventilation and heat dissipation system all adopt imported axial fans, which are ultra-quiet, long-life, and have strong wind power. Ensure that the motor is effectively dissipated at any speed, and can achieve long-term operation at high or low speeds.

Compared with the traditional inverter motor, it has a wider speed regulation range and higher design quality, and the high-order harmonic magnetic field is further suppressed through a special magnetic field design to meet the design indicators of wide frequency, energy saving and low noise. It has a wide range of constant torque and power speed regulation characteristics, stable speed regulation, no torque ripple.

The working principle of the variable frequency motor: three symmetrical windings, three symmetrical alternating current, will generate a rotating magnetic field in space, this magnetic field cuts the rotor conductor, will generate induced electromotive force and induced current in the rotor, and the rotation speed is lower than the synchronous speed and rotates in the same direction as the synchronous speed. The inverter motor is to change the speed of the motor by changing the frequency of the input three-phase alternating current, and the inverter is used to regulate the speed.

The variable frequency motor adopts the AC speed regulation mode of "special variable frequency induction motor + frequency converter", which greatly improves the degree of mechanical automation and production efficiency, greatly improves the miniaturization of equipment and increases comfort, and is currently replacing the traditional mechanical speed regulation and DC speed regulation scheme.

The inverter motor is a kind of synchronous motor, and the speed is related to the frequency of the power supply. In addition, a frequency converter is used to turn the power frequency alternating current of 50Hz into alternating current with variable output frequency.