Capacitors, as one of the most widely used electronic components, have a very wide range of functions. One of these functions is filtering, which is a very common function of capacitors. Filter capacitors can perform reactive power compensation, improve power factor, reduce active power losses in the grid and reduce voltage, and are therefore widely used in power systems. What issues need to be taken into account when making filter capacitors? What is the role of filter capacitors? Next, take a look at it together.
The rated voltage of the capacitor must match the voltage of the grid it is connected to:The long-term operating voltage of the capacitor must not exceed 5% of the rated voltage, and the transient overvoltage must not exceed 10% of the rated voltage. When there are harmonics in the grid, the working current of the capacitor must not exceed 30% of the rated current. If the rated parameters are not reasonable, it will mislead the selection of capacitors, which can easily lead to malignant accidents such as expansion or even explosion during the operation of the capacitors.
Install in strict accordance with the prescribed wiring: if the rated voltage is the same as the grid voltage, the delta wiring method should be used. If the rated voltage is not the same as the grid voltage, the star wiring method should be used. Double Y wiring is usually used for the balanced protection of internal capacitors. If the wiring method is not reasonable, it will lead to accidents such as overvoltage and overcurrent of the capacitor.
The temperature of the capacitor's working environment should be appropriate: temperature is also one of the key factors affecting the safe operation of capacitors, so when running a capacitor, you need to ensure that its ambient temperature is maintained in a suitable state.
What do I need to pay attention to when making a filter capacitor? What is the role of the filter capacitor?
Filter capacitors are mainly used in power rectification circuits to filter out the AC component. This makes the output DC smoother. For precision circuits, a combination of parallel capacitor circuits is often used to improve the filtering effect.
Filter capacitors work at different operating frequencies depending on the low and high frequencies.
The low frequency filter capacitor is mainly used for filtering after mains filtering or transformer rectification, and its working frequency is 50Hz in line with mains; while the high frequency filter capacitor mainly works for filtering after rectification in switching power supply, and its working frequency is several thousand Hz to several tens of thousands of Hz.
The filter capacitor plays a very important role in the switching power supply, how to choose the correct filter capacitor, especially the choice of output filter capacitor is a matter of great concern to every engineer and technician.
The common electrolytic capacitor used in 50 Hz frequency circuits has a pulsation voltage frequency of only 100 Hz and a charge and discharge time of the order of milliseconds.
In order to obtain a smaller pulsation factor, the required capacitance is up to hundreds of thousands of microfarads, so the objective of ordinary low frequency aluminium electrolytic capacitors is to increase the capacitance, the capacitance, the loss angle tangent and the leakage current are the main parameters to identify their merits.
The output filter electrolytic capacitors in switching power supplies, on the other hand, have a sawtooth voltage frequency of tens of thousands of hertz, or even tens of megahertz.
At this point the capacity is not the main indicator, but rather the "impedance-frequency" characteristic of the high frequency aluminium electrolytic capacitor. The requirement is to have a low equivalent impedance within the operating frequency of the switching power supply, and to have a good filtering effect on the high frequency spikes generated by the semiconductor devices.
Ordinary low frequency electrolytic capacitors start to show inductance at around 10,000 Hz and cannot meet the requirements of switching power supplies.
The high-frequency aluminium electrolytic capacitor for switching power supplies has four terminals, with the two ends of the positive aluminium piece leading out as the positive terminal of the capacitor and the two ends of the negative aluminium piece also leading out as the negative terminal. Current flows from one of the positive terminals of the four-terminal capacitor, through the inside of the capacitor, and then from the other positive terminal to the load; the current returning from the load also flows from one of the negative terminals of the capacitor, and then from the other negative terminal to the negative side of the power supply.
I believe that by reading the above, you have a preliminary understanding of filter capacitors, and I also hope that you will do a good job of summarizing the learning process so that you can continuously improve your professional level. In general, the role of filter capacitors as described in the name is obviously mainly for filtering.
