You should know these if you are engaged in motor-related work PART 1

- May 15, 2018 -

You should know these if you are engaged in motor-related work

After contacting many customers who purchased the motor, they collected some questions asked by the customers and related answers to the technology. Perhaps you will also encounter such confusion when using a motor or replacing a motor. When purchasing a motor, there are several keywords, common motor, aluminum motor, variable frequency motor, three-phase asynchronous motor, vertical installation, horizontal installation, motor power, voltage, DC motor, AC motor, etc. .

1. Why is an earth leakage circuit breaker tripping easily when using a frequency converter?

This is because the inverter's output waveform contains higher harmonics, and the motor and the cable between the inverter and the motor generate a leakage current. This leakage current is much larger than the power frequency drive motor, so this phenomenon occurs.

Leakage current at the output side of the inverter is about 3 times more than that at the power frequency operation. Leakage current such as a motor is added. The operating current of the leakage protector should be greater than 10 times the leakage current at the power frequency.

2. I want to do the experiment of motor frequency conversion speed control. Can the ordinary motor realize frequency conversion speed regulation? Or must I buy a variable frequency motor?

To do the motor frequency conversion speed test with the ordinary AC motor on the line.

DC motors can also be frequency-converted. For example, DC inverter air conditioners nowadays convert AC power to DC power and send them to the power module. The module is controlled by the control signal sent from the microcomputer. The difference between the AC and the inverter is that the module output is affected. The controlled DC power is sent to the DC motor of the compressor to control the displacement of the compressor so as to achieve "frequency control."

3. What kind of motor is an AC variable frequency motor?

In simple terms, inverter technology is used in the control of AC motors. AC frequency conversion motor is actually a kind of motor that adjusts the frequency of AC power to adjust the speed. The frequency of AC power adjustment depends on the inverter. The motor itself will not be frequency-converted. In many occasions where the requirements are not high, it is to take the common motor and inverter to adjust the speed. Variable frequency motor use.

4. Is the inverter single-phase 220v to three-phase 380v?

It is not possible. The inverter itself cannot boost the voltage, and it can't change three-phase 380v from single-phase 220v. This is theoretically feasible, using a transformer to raise the single-phase 220V to 380V, and then converting the single-phase 380V to three-phase 380V.

5. The belt that the high-power motor drags has a speed reducer connected with the motor. The function of the speed reducer is here?

The purpose of the reducer can be summed up briefly:

Reduce the speed and increase the output torque at the same time. The output ratio of the torque output will be multiplied by the speed reduction pen, but be careful not to exceed the rated torque of the speed reducer.

Deceleration also reduces the inertia of the load. The reduction in inertia is the square of the reduction ratio. We can see that the general motor has an inertial data.

6. What is the reason for the slow speed of the motor starting?

If only the start speed is slow, normal after starting. This may be caused by a mismatch in the starting capacitor, or by the fact that the motor design is originally designed (according to the design of the site), or it may be due to factors such as excessive load resistance and excessive start-up times.

If the speed is slow after start-up, the problem may be that the voltage is insufficient, the capacitance does not match, and the rotational resistance is large.

7. How to choose the brush of rotor winding bushing of induction motor?

The determination is mainly based on whether the working condition of the brush satisfies the current density (A/cm2) and the linear velocity (m/s) of the peripheral edge of the collector ring.

Determine the formula:

Brush carrying capacity (A) = brush current density (A/cm2) × brush width L (cm) × brush thickness b (cm) ≥ motor rotor rated current (A);

The circumferential speed of the collector ring circumferential edge (m/s) = motor rated speed (r/m)/60(s) × collector ring perimeter (m) ≤ brush applicable range (m/s).

Its commonly used brushes are non-ink brush, electrochemical graphite brush and metal graphite brush. During use, attention should be paid to checking brush activity, brush pressure and wear. The brush should be able to move freely up and down in the brush holder without any jamming. When brushing the brush, both sides of the brush can be smoothed on the emery cloth. The pressure of the brush should be properly adjusted according to the type and model of the brush. At present, the brush pressing spring attached to the brush holder is mostly a tension and compression spring, and the pressure thereof gradually decreases as the brush wears, so the brush pressure during the operation of the motor should be adjusted at any time.

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