The application problems of inverter motors, the advantages of inverter motors

Yes, there is an option to drag with a variable frequency.

The medium you said will cause the problem of motor stalling, which can be solved, the simple way to do is to use the overcurrent and loss speed protection function of the inverter, when the load exceeds the motor torque, the inverter will reduce the output until the output current is within the rated range, of course, you need to set the inverter according to the actual parameters of the motor, including the rated current of the motor, acceleration and deceleration time to choose a suitable value.

There is no need to purchase a variable frequency motor, and ordinary motors can also meet your requirements. No sensors or anything.

As for how much, this is really difficult, depending on how much power your pump is, if it is only 4kw, then it will be 1500-2500 yuan, and it will be about 3000; This is the ** of the domestic inverter, actually**, you can consult the merchant, ask more, and now** is very transparent.

In the selection of inverter, you can choose according to the motor power (or rated current), if it is a large or high-voltage motor, then you need to explain it clearly to the business.

For medium pumps, your inverter is best to choose a heavy-duty inverter, which is one level larger than the motor, and the inverter control can completely avoid burning the motor! When the current is too large, the frequency converter will generally reduce the frequency first to reduce the output current of the frequency converter (determined by the stall prevention level of the frequency converter) **Problem: Domestic and imported products** are a lot worse It is recommended to choose imported ones to save trouble in later maintenance!

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.

Summary. The influence of the passive rotation of the motor on the inverter mainly depends on the specific situation of the passive rotating motor and the quality of the inverter. In general, passive rotation of the motor will generate back EMF in the inverter and cause current backflow, which may adversely affect the inverter, such as voltage increase, temperature rise, etc.

Therefore, the passive rotation of the motor should be avoided as much as possible, and devices such as brakes can be used to limit the rotation of the motor. If the passive rotation of the motor cannot be avoided, it is necessary to choose a high-quality inverter with feedback current control and overcurrent protection to ensure that the motor and the inverter have better matching and electrical performance, and reduce the impact of passive rotation on the inverter.

The influence of the passive rotation of the motor on the inverter mainly depends on the specific situation of the passive rotating motor and the quality of the inverter. Generally speaking, the passive rotation of the motor will generate back electromotive force in the inverter and cause current backflow, which may adversely affect the inverter, such as voltage increase, temperature rise, etc. Therefore, the passive rotation of the motor should be avoided as much as possible, and the brakes and other devices can be used to limit the rotation of the motor.

If the passive rotation of the motor cannot be avoided, it is necessary to choose a high-quality inverter with feedback current control and overcurrent protection to ensure that the motor and the inverter have better matching and electrical performance, and reduce the impact of passive rotation on the inverter.

You've done a great job! Can you elaborate on that?

The passive rotation of the motor may have an adverse effect on the inverter, which mainly depends on the specific situation of the passive rotation of the motor and the quality of the inverter. When the motor rotates passively, a back EMF is generated in the inverter and the current is returned. If the reflow is large, the cavity mode current is large, which may have an impact on the inverter, such as voltage increase, temperature rise, etc.

Therefore, in order to avoid this from happening, measures can be taken to limit the rotation of the motor, such as installing devices such as brakes. In addition, high-quality inverters that meet the requirements should be selected, which have functions such as feedback current control and overcurrent protection, which can ensure that the motor and inverter are better in terms of electrical performance and matching, and reduce the adverse effects of passive rotation on the inverter. To sum up, taking corresponding measures can effectively reduce the impact of passive rotation of the motor on the inverter.

For ordinary asynchronous motors, the main performance parameters considered in the design are overload capacity, starting performance, efficiency and power factor. The variable frequency motor, because the critical slip rate is inversely proportional to the power supply frequency, can be started directly when the critical slip rate is close to 1, therefore, the overload capacity and starting performance no longer need to be considered too much, and the key problem to be solved is how to improve the adaptability of the motor to the non-sine wave power supply.

1) Reduce stator and rotor resistance as much as possible. Fundamental copper losses can be reduced by decreasing the stator resistance to compensate for the increased copper losses caused by higher harmonics.

2) 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 its skin effect is also large, 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.

3) 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; The second is to consider that in order to increase the output torque at low frequency, the output voltage of the inverter should be appropriately increased.

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

4) insulation grade, generally F or higher, strengthen the insulation strength of ground insulation and wire turns, especially the ability of insulation to withstand impulse voltage.

5) For the vibration and noise problems of the motor, the rigidity of the motor and the whole should be fully considered, and the natural frequency should be increased as much as possible to avoid the resonance with each harmonic.

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

7) Measures to prevent shaft current, bearing insulation measures should be adopted 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 significantly, resulting in damage to the bearing, so insulation measures should generally be taken.

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

In terms of motor energy saving, the high-voltage motor power-saving system independently developed by Zhongke Yujie is based on high-voltage inverter, and the high-voltage inverter adopts power unit series connection technology to directly output 6kV and 10kV voltage. Since the power unit is connected in series instead of the direct series connection of the power device, the problem of device withstand voltage is solved. The main control part adopts DSP + FPGA (i.e., field programmable gate array) + PLC large-scale high-speed integrated digital circuit control mode, and high-speed computing can achieve real-time accurate motor control, achieving the purpose of taking into account high performance and high reliability.

The core control algorithm adopts the space vector PWM control algorithm, which effectively improves the DC voltage utilization rate, and the FPGA realizes the pulse distribution algorithm of the power unit, which drives the power unit in real time and quickly drives the power output of all units. Reduce energy consumption and improve motor efficiency.

Variable frequency motor: a motor that can be adjusted at any speed within its speed range.

The working principle of the inverter motor: The circuit of the inverter motor is generally composed of four parts: rectification, intermediate DC, inverter and control. First, the power frequency AC power supply is converted into DC power supply through the rectifier, and then the DC power supply is converted into AC power supply with controllable frequency and voltage to supply the motor.

Advantages of inverter motors:

1. It has a starting function;

2. Electromagnetic design is adopted to reduce the resistance of stator and rotor;

3. Adapt to frequent speed changes under different working conditions;

4. Energy saving to a certain extent;

5. The use of polymer insulation materials and special insulation structure greatly improves the insulation voltage resistance and mechanical strength.