SHDR Capacitors 680UF200V High Voltage Power Aluminium Electrolytic Capacitor

Application Factors Affecting Lifespan

According to the life formula, the application factors affecting the life can be obtained as follows: ripple current (IRMS), ambient temperature (Ta), total thermal resistance from thermoelectric transfer to the surrounding environment

(Rth).

  1. Ripple current

  The magnitude of the ripple current directly affects the hot spot temperature inside the electrolytic capacitor. Check the user manual of electrolytic capacitors to get the allowable range of ripple current. If it exceeds the range, it can be solved in parallel

 2. Ambient temperature (Ta) and thermal resistance (Rth)

     According to the formula of cooked electricity temperature, the application environment temperature of electrolytic capacitors is also an important factor. In application, environmental dissipation methods, heat dissipation intensity, distance between electrolytic capacitors and heat sources, and installation methods of electrolytic capacitors can be considered.

   The heat inside the capacitor is always conducted from the hottest "hot spot" to the relatively cooler surrounding part. There are several ways of heat transfer: one is conduction through aluminum foil and electrolyte. If the capacitors are mounted on the heat sink, a portion of the heat will also be transferred to the environment through the heat sink. Different mounting styles and spacing and heat dissipation will affect the thermal resistance of the capacitor to ambient. The total thermal resistance from the "hot spot" to the surrounding environment is denoted by Rth. Using clip mounting, install the capacitor on a heat sink with a thermal resistance of 2°C/, and the obtained thermal resistance value of the capacitor Rth=3.6°C/w: Install the capacitor on a screw mount with a thermal resistance of 2°C /W on the heat sink, forced air cooling speed

When the rate is 2m/s, the obtained capacitor thermal resistance value Rth=2.1°C/W.

(Take PEH20000427AM type capacitor as an example, the ambient temperature is 85°C)

   In addition, it is also a good method to reduce thermal resistance by directly contacting the extended cathode aluminum foil with the capacitor aluminum shell. At the same time, it should be noted that the aluminum shell will be negatively charged and cannot be negatively charged.

pole connection.

  A capacitor must be installed correctly to achieve its designed operating life. For example: RIFA PEH169 series and PEH200 series should be installed vertically upward or horizontally.

At the same time, make sure that the safety valve is facing upwards, so that the hot electrolyte and vapor can be discharged from the safety valve smoothly when the capacitor fails.

  When the capacitor arrangement is very tight, there should be at least 5mm space between adjacent capacitors to ensure proper air flow. Nut torque control is very important when using bolted installations. If it is screwed too loosely, the capacitor and the heat sink will not be in close contact; if it is screwed too tightly, the threads may be damaged. At the same time, it should be noted that the capacitor should not be installed upside down, otherwise the bolts may be broken.

The capacitor should be installed as far away as possible from the heating element, otherwise the high temperature will shorten the service life of the capacitor, thus making the capacitor the component with the shortest life in the entire circuit. In the case of high ambient temperature, try to use forced air cooling and install the capacitor at the air inlet.