What is difference between inverter motor and ordinary motor

Problem a:

Differences between frequency conversion motor and ordinary motor:

One, frequency conversion motor and common motor on the whole there are three main differences

1. Different heat dissipation system; Common fan cooling fan and fan movement with the same line, and frequency conversion motor in these two are separate. So the common fan frequency conversion is too low, may burn off because of overheating.

2. Due to the high frequency magnetic field under 2, frequency conversion motor, so the insulation class is higher than the general motor, in principle, general motors can’t use frequency converter to drive, but in practice, in order to save money, in many need speed occasions instead of using ordinary motor frequency conversion motor, but ordinary motor speed control precision is not high, often in the energy-saving reconstruction of fan and water pump to do so.

When the frequency conversion motor is replaced by a common motor, the carrier frequency of the frequency converter is as low as possible to reduce the insulation damage of the motor caused by high frequency. Frequency conversion motor to strengthen the insulation of the slot, one is to strengthen the insulation material, one is to increase the thickness of the insulation of the slot, in order to improve the level of high frequency voltage.

3. Increased electromagnetic load. The working point of common motor is basically at the inflection point of magnetic saturation. If used as frequency conversion, it is easy to saturate and generate high excitation current. However, the frequency conversion motor increases the electromagnetic load in the design, making the magnetic circuit not easy to saturate. In addition is the frequency conversion motor is generally divided into the constant torque motor, used for feedback vector control with speed measuring device of the special motor and intermediate frequency motor.

Two, ordinary motor and frequency conversion motor design differences

1. Electromagnetic design

For ordinary asynchronous motor, and the design main consideration of the performance parameter is the overload capacity, starting performance, efficiency and power factor. And frequency conversion motor, because of the critical slip inverse ratio at power frequency, you can directly start when critical slip is close to 1, therefore, overload capacity and startup performance is not need to think too much, and to solve the key problem is how to improve the ability to adapt the motor of the non sine wave power.

2. Structural design

In structure design, main is to consider the insulation of the non-sinusoidal power characteristics of frequency conversion motor structure, the influence of vibration and noise cooling way, etc.

Three, ordinary motor and frequency conversion motor measurement differences

1. The actual output waveform of the converter is PWM wave, which includes carrier signal in addition to the fundamental wave. The carrier signal frequency is much higher than the fundamental wave, and it is a square wave signal, which contains a lot of higher harmonics. For the test system, higher sampling frequency and bandwidth are required.

2. In the environment powered by frequency converter, various high-frequency interference is everywhere, and electromagnetic interference is much stronger than power frequency environment, which requires stronger ELECTROMAGNETIC compatibility of the test system.

3. The peak factor of PWM wave is generally high, and ordinary instruments fundamentally meet the requirements. For the frequency conversion test system, higher measurement capability of peak factor is required.

4. The instrument used for frequency conversion test should be able to decompose its fundamental wave in various PWM waveforms. In strict measurement, digital signal processing should be adopted, that is, high-speed sampling is required to obtain the sample sequence, and then discrete Fourier transform is performed on the sample sequence to obtain the amplitude and phase of the fundamental wave with amplitude, phase and various harmonics.

As far as the mainstream instrument of frequency conversion measurement is concerned, Hall sensor and frequency conversion power analyzer is a choice method of many manufacturers. However, the limitation of this method is constantly expanding, which is mainly manifested in the difficulty in solving the interference problem of transmission link, which is the fatal flaw of this measurement method. The power analyzer based on front-end digitization can solve this problem well, which will become the main method of frequency conversion measurement in the future.

The reason for the energy saving of the inverter motor is not the low loss of the inverter motor, but the increase of the stator copper consumption, rotor copper consumption, iron consumption and additional loss will be caused by high harmonic wave under the non-sinusoidal voltage and current.

Frequency conversion motor energy conservation is through the use of constant speed to adapt to different environment, in order to achieve the goal of reducing unnecessary loss, if running at the same time in the environment, the power frequency conversion motor with ordinary motor not much of a difference, even more energy frequency conversion motor, that is to say we can’t blindly believe in variable frequency energy saving of the propaganda.

Problem two:

Ordinary motor, if the frequency is changed by frequency converter, will have the following effects:

If you are referring to an AC asynchronous motor, the speed of the motor changes accordingly by changing the output frequency through a frequency converter. The influence on the motor itself does include heating, possible insulation breakdown, insufficient torque at too high speed and too low speed, etc.

There are mainly several reasons for the heating of the motor itself:

First, the cooling fan and motor spindle of some motors are coaxial, after reducing the speed, cooling fan speed decline leads to bad heat dissipation, it is possible to burn the motor.

Secondly, there are some problems in the hardware and software of some frequency converters. The output du/ DT is too large, leading to too large DI/DT, which may lead to inter-turn breakdown or heating phenomenon, resulting in motor burning at last.

What is difference between inverter motor and ordinary motor

Extension:

Frequency is the number of vibrations completed per unit time. For the motor, the frequency usually refers to the frequency of the ac input power supply of the motor, and the frequency of the applicable power supply for domestic equipment is mostly 50HZ.

1. The role of frequency
For ac motors, frequency and speed are proportional, that is, the higher the frequency, the faster the rotation, the lower the frequency, the slower the rotation.

2. Influence of frequency conversion on motor
Frequency converter, is a change of equipment input power frequency of power supply equipment, that is, the frequency converter installed in the ac power supply and electrical equipment between, from the power grid to the alternating current, first through the frequency converter, out of the variable frequency alternating current supply motor.

Frequency converter can be understood as a speed regulating device. In practical use, it is mainly used to adjust the output of the motor according to the working condition of the motor, so as to meet the technical requirements. At the same time, for the specific working condition of the motor, this way of frequency conversion to adjust the speed has a certain energy saving effect compared with the traditional way of mechanical speed adjustment.

3. Heating problem after frequency conversion of frequency converter
Motor using frequency converter, because the inverter itself is a power electronic equipment, after the power supply of rectifier and inverter output current harmonic content is higher, the harmonic will make the motor stator winding and iron core produce certain heat problem, usually, the increase of the fever no significant damage to equipment.

However, for the load with large power, such as the AC motor with 3000KW or more, it is necessary to consider using a specially designed frequency conversion motor, that is, the motor itself has a cooling system with forced air cooling or water cooling, so as to avoid excessive bearing temperature of the motor and damage the equipment in the process of use.

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