Why can t the inverter output be connected to a capacitive load

1. If there is a capacitor in the inverter, as long as there is no problem with the inverter itself, it can be connected to the load for normal operation;

2. If the load to be connected behind the inverter is capacitive, it is not recommended to use it in this way, there are clear requirements in the inverter manual, and the capacitive load is not allowed behind the inverter, otherwise, it is easy to damage the inverter module of the inverter;

3. If the load dragged by the inverter has capacitance, but the capacitor is not directly connected to the three terminals of the inverter, such as U, V, and W, and the capacity is not particularly large, it is possible. Just like the MLAD-SW sine wave filter contains a filter capacitor component, as long as the scattering parameters are selected appropriately, the normal operation of the inverter will not be affected.

A capacitive load is equivalent to a short circuit for an inverter power tube, because the voltage of the capacitor cannot be abruptly changed.

Because the output voltage of the inverter is PWM square wave, it contains many higher harmonic components. Because the capacitive reactance of the capacitor under the higher harmonic is smaller, the higher harmonic current is larger, which increases the burden on the inverter transistor on the one hand, and on the other hand, the capacitor itself is also easy to be damaged due to overheating.

The inverter works in the switching state, such as the capacitor, at the moment when the inverter is turned on, there will be a large peak charge current or discharge current (which is why our inverter needs to have a charging resistance after rectification, and the reason for the short circuit after charging), so that the inverter is damaged. Therefore, similar capacitive loads cannot be plugged in.

The output is a low-frequency wave containing higher harmonics. The reactance of the motor smooths the low-frequency waveform.

The capacitance is approximately short-circuited relative to high frequencies. So I can't pick it up.

Because we still use the low frequency of frequency conversion output (the maximum motor is 50Hz).

That's not true.

If the single-phase inverter does not add any measures, it must not be connected to the single-phase capacitor started motor. This is because the output characteristics of the inverter are determined, and the inductance characteristics of the motor are considered in the design of the inverter. The output of the inverter is a high-frequency PWM pulse, which is a modulation of the low-frequency voltage with a pulse width of more than a dozen KHz high-frequency pulses.

If the motor is a capacitive single-phase motor, the principle of this motor itself is to use the phase advance characteristics of the capacitor to phase shift the starting winding voltage of the motor, so as to generate a rotating magnetic field in the motor stator and drive the motor. Once the inverter is directly connected to it, the high-frequency pulse is a path for this capacitor, and cannot play the role of phase shifting, which is equivalent to the main winding and the starting winding are connected to the voltage at the same time, but cannot produce a rotating magnetic field. The motor current will increase dramatically due to the stalled, which will burn the inverter IGBT module and the motor.

The carrier frequency of the inverter is relatively high, and it is a harmonic, and if you connect a capacitor, it is equivalent to grounding.

Yes, you can't connect the capacitor, the instantaneous voltage of the capacitor is zero, so the current is very large, the IGBT is unbearable, of course, these are all theoretically said, you can do a test to try, set the voltage to the lowest to play, the mains is generated by the generator, different.

The alternating current coming out of the inverter has higher harmonics, so the capacitor cannot be added at the output end. After the single-phase motor is connected to the output terminal, the three-phase imbalance will be detected inside the inverter, resulting in a phase loss alarm in the output of the inverter. The mains power does not have the above problems. The above is for reference.

It is considered in two parts.

The capacitor should represent the capacitor used to compensate the motor for reactive power, which is a capacitive single-phase motor connected in parallel, the capacitor is used to deal with the armature and the winding phase angle, and the single-phase inverter has included the control function.

Personal opinions are for reference only.

It mainly depends on how you connect, whether it is a question of parallel or series.

No load, there is a start command, there is a given speed, correspondingly at the output of the inverter, the voltage can be measured If there is no start command, or the speed is 0, then the voltage is also 0.

A load is an electronic component that is connected to both ends of a power supply in a circuit. The power supply poles should not be connected directly without a load in the circuit, and this connection is called a short circuit. Commonly used loads are resistors, engines, and power-consuming components such as light bulbs.

A device that converts electrical energy into other forms of energy is called a load. Electric motors can convert electrical energy into mechanical energy, resistors can convert electrical energy into heat, light bulbs can convert electrical energy into heat and light energy, and loudspeakers can convert electrical energy into sound energy. Motors, resistors, light bulbs, speakers, etc., are all called loads.

The transistor can also be seen as a load for the previous signal source. The most basic requirements for a load are impedance matching and the amount of power it can withstand.

I not only use an inverter, but I also make an inverter. Tell you for sure, there is an output. The output voltage is basically the same as the on-belt load.

The frequency converter may have an impact on the life of the capacitor in the capacitor compensation cabinet. The correct way is to add a reactor at the input end in the capacitance compensation cabinet and a reactor at the input end of the frequency conversion cabinet. This is the latest practice. The main benefits are:

1. Limit the current impulse caused by the sudden change of grid voltage and operating overvoltage, smooth the spike pulse contained in the power supply voltage, or smooth the voltage defects generated during the commutation of the bridge rectifier circuit, and effectively protect the inverter;

2. Improve the power factor, which can not only prevent the interference from the power grid, but also reduce the pollution of the power grid by the harmonic current generated by the rectifier unit.

3. Improve the influence of three-phase voltage imbalance on the inverter.

The inverter is a purely resistive load compared to the power supply, and the compensation basically does not work, but it seems that there is no harm.

This application can easily cause damage to the frequency converter, and if the isolation barrier is not applied, it will cause great interference.

The harmonic current of the inverter will cause harmonic resonance in the power distribution system with capacitor compensation, which is very harmful.

The solution is to connect about 6% of the reactor in series on the reactive power compensation capacitor.

1 There are a large number of harmonics in the system.

2. It is easy to resonate in series with the system.

3 Cause the heat of the transformer to increase and may reach more than 100 degrees Celsius 4 Affect the safe and stable operation of all production equipment in the system, the direct result is the increase in noise and temperature rise.

5. Affect the normal operation of switches and fuses.

6. Affect the production process of the product.

If the output capacitor is installed on the side of the inverter, or if the output line is far away (generating distributed capacitance), it is easy to cause instantaneous overcurrent and even damage the internal power tube of the inverter.

If you want to improve the power factor or compensation circuit, you can choose an inductive L-filter if necessary.

An optional EMI filter can also be installed on the output side to suppress RF interference noise and wire leakage current generated by the inverter output.

One of the characteristics of capacitors is charge and discharge. When the inverter first starts running, the power output will be absorbed by the capacitors, causing the load to not work properly. When the inverter stops running, at this time, the output power of the inverter is zero, and the capacitor will be discharged, and the released electric energy will be directly applied to the inverter module of the inverter, which will cause the inverter module of the inverter to be damaged.

This is also the reason why all inverter manufacturers must emphasize in the user manual: the inverter cannot drive capacitive loads!

Because the output voltage of the inverter is a rectangular pulse train, it contains many higher harmonic components. Since the capacitive reactance of the capacitor under the higher harmonic is smaller, the higher harmonic current is larger, which increases the burden on the inverter transistor on the one hand, and on the other hand, the capacitor itself is also prone to damage due to overheating. If there are any problems with the inverter, you can go to the China Self Network to learn about the relevant knowledge.

1.In general, the main circuit, the filter circuit of the inverter is added between the power supply and the inverter, and the inverter and the motor can be connected with a shielded cable.

2.If you want to improve the current waveform, you must use an inductor rather than a capacitor for the following reasons:

The quasi-sine wave signal after the inverter inverts the current output by the inverter, which is actually a pulse signal.

The role of the inductor is to suppress the sudden change of current, and the capacitor is to suppress the sudden change of voltage, so when improving the current signal, our choice should be the inductor rather than the capacitor.

There are already a lot of capacitors in the inverter, and the current waveform inverter can be controlled by itself, and filters can be added.