Capacitor Percentage Rating

The capacitor should be capable of smooth operation upto 110 of rated peak phase voltage of the system and also it should be capable of operation 120 of rated rms phase voltage that means 120 of times of peak phase voltage. Currently polymer tantalum capacitors have two category temperature classes including 105 degrees c and 125 degrees c.

Capacitor Input Filter Calculation

Analog On Ceramic Capacitors

Why You Should De Rate Capacitors

As with resistors capacitors also have a tolerance rating expressed as a plus or minus value either in picofarads pf for low value capacitors generally less than 100pf or as a percentage for higher value capacitors generally higher than 100pf.

Capacitor percentage rating. For voltage ratings greater than 10 volts a 20 derating is recommended. See below for a list of letter style tolerance codes. Calculate the required capacity of capacitor in both kvar and farads.

For example a capacitor labeled 6000uf 50 70 could actually have a capacitance as high as 6000uf 6000 05 9000uf or as low as 6000 uf 6000uf 07 1800uf. The voltage rating is only the maximum voltage that a capacitor should be exposed to not the voltage that the capacitor will charge up to. Both of the capacitors have a temperature rating of 105 o c so if the operating temperature is estimated at 75 o c which is high for this system there is a 30 o c difference between the rated and the operating temperature.

If there is no percentage listed look for a single letter after the capacitance value or on its own line. For less than or equal to 10 voltage ratings a 10 derating is recommended. If it is a little lower it is still a good capacitor.

The motor power factor has to be improved to 09 by connecting a capacitor in parallel with it. Voltage rating of capacitor bank a capacitor unit is normally designed for single phase. Due to tolerance and the fact that specifically electrolytic capacitors may dry up you may read a little less in value than the capacitance of the rating.

A single phase 400v 50hz motor takes a supply current of 50a at a pf power factor of 06. A capacitor may have a 50 volt rating but it will not charge up to 50 volts unless it is fed 50 volts from a dc power source. This may be code for a tolerance value described below.

You should read a value near the capacitance rating of the capacitor. The letter z donates a tolerance of 80 percent and 20 percent. That means the capacitor which is rated at 1 mf might be as much as 80 percent higher or 20 percent lower.