Customized Power Electronic Photovoltaic 600VDC~2200DC Inverter DC Starting Capacitors

Product Description

Customized Power Electronic Photovoltaic 600VDC~2200DC Inverter DC Starting Capacitors
 
  

• Compensate for the difference between the power required by the inverter and the output power of the rectifier bridge that changes by two or six times the power frequency;

 

• Provide input current of switching frequency of inverter or freight frequency converter;

 

• Reduce the current harmonic of switching frequency into the power grid;

 

• Absorb the demagnetization energy of the motor when all power switching devices are turned off in the emergency stop state;

 

• Provide instantaneous peak power;

 

• Protect the inverter or frequency converter from the impact of the instantaneous peak value of the power grid.

 

  

Capacitors can be used to provide significant ride-through (or hold) energy, or to reduce ripple and noise in power conversion circuits. Choosing the right type of capacitor can have a profound impact on the overall size, cost, and performance of the system. This article will discuss the advantages of film and electrolytic capacitors in some common applications.

 

Film and Electrolytic Capacitors: A Basic Comparison

 

Film capacitors have low Equivalent Series Resistance (ESR), resulting in good ripple current handling, as well as high surge voltage ratings and self-healing performance, and are used in many important applications such as electric vehicles, renewable energy, and industrial drives. A strong contender for power regulation tasks. Film capacitors are especially suitable for applications where hold (or ride-through) is not required, such as between power outages or line frequency fluctuation peaks, where large high-frequency ripple currents need to be supplied or absorbed with high reliability and low losses.

 

Film capacitors are also ideal for applications operating at high DC bus voltages to minimize resistive losses. Since aluminum electrolytic capacitors can only provide voltages rated up to about 550V, applications operating at higher voltages require multiple devices to be connected in series, after which it is necessary to prevent voltage unbalance by choosing capacitors with matching values, this method Expensive and time-consuming; or add voltage balancing resistors, which add extra energy loss and BOM cost.

 

On the other hand, aluminum electrolytic capacitors are still a strong choice when pure energy storage density (J/cm3) is the main parameter of interest. One example is commercial off-line power supplies that require cost-effective bulk energy storage to maintain DC output voltage during power outages without the need for backup batteries. Appropriate derating can reduce issues such as life and reliability of aluminum electrolytic capacitors.

 

However, in fact, aluminum electrolytic capacitors can only withstand an overvoltage of about 20%, and if there is a higher overvoltage, damage will occur, while film capacitors can withstand an overvoltage of up to about twice the rated voltage for a short period of time. The self-healing capability ensures a safer reaction to accidental overpressure, as is often encountered in practical applications.

 

There are other reasons why film capacitors are the best choice. The parallel connection of multiple electrolytic capacitors results in excessive capacitance, which may cause problems such as controlling the energy in the inrush current. Additionally, where transient overvoltages on the DC link are common in light-duty traction applications such as electric vehicles, film capacitors are more robust.

 

Similar analyses apply to applications such as UPS systems, power conditioning for wind or solar generators, general-purpose grid-tied inverters, and welding machines. If matching these power systems is required, film capacitors are preferred.

 

Repair of power capacitors

The following faults can be repaired by themselves at the installation site:

1)The oil leakage on the casing can be repaired with tin-lead solder.

2)The oil leakage at the welding seam of the casing can be repaired with tin-lead solder, but it should be noted that the soldering iron cannot be overheated to prevent the silver layer from being de-soldered.

• The capacitor has insulation breakdown to the ground, the loss tangent value of the capacitor increases, the case expansion and open circuit failures, etc., need to be repaired in a factory with special capacitor repair equipment.

 

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