Some notes on the performance of capacitors used in lamps and ballasts

First, the loss and detection of film capacitors

The loss of a capacitor is composed of dielectric loss and metal loss. The dielectric loss is determined by the medium itself, that is, by the performance of the dielectric film - leakage. When the frequency of use is low, the loss of the capacitor is mainly determined by the dielectric loss. Its value decreases inversely with increasing frequency, see illustration:

(Leakage: Any dielectric is not an ideal insulator. Under the action of an electric field, there is always a certain current flowing. This current is very small, called leakage current or leakage.)

Metal partial loss, the formula is: tgδ = ωcR _s = 2πfcR _s (R is the equivalent series resistance of the capacitor), so when the frequency of use is high, the metal part loss is the main loss. R _s is the sum of the contact resistance caused by the connection between the capacitor lead line resistance, the plate resistance, and the plate and the lead line. If the connection is not good and the contact resistance is large, the loss of the capacitor at high frequencies is large. The capacitor is used under high frequency conditions, causing severe heat generation and damage. Therefore, when the frequency of use is high, high-frequency testing must be used to eliminate those with poor end contact. Try to eliminate the potential dangers of use. The low frequency 1KHz can not effectively eliminate the bad contact, and the CBB class 1KHz loss index is ≤0.0003, the value is too small, sometimes the error between the test instruments may reach 0.0002. Therefore, it is recommended to use at least 10KHz when using the lamp with higher frequency of use, the index is ≤0.0010, more sure. Our company supplies the manufacturers of lamps and ballasts to Shanghai Matt, Shanghai Guangda, Jiangsu Baijiali, Shenzhen Haoyun, Hengyao Electric, Zhongshan Oup, all with 10KHz testing, and they have been guaranteed for many years. Intact use.

The operating voltage of the capacitor should generally not be greater than the rated voltage when the frequency is suitable. The instantaneous withstand voltage, that is, the withstand voltage, according to the international and domestic standards, the maximum detection voltage is twice the voltage. Repeated voltage withstand test is harmful to the capacitor. Therefore, the excessive withstand voltage exceeds the tolerance of the dielectric film, which will damage the dielectric to the capacitor. Adverse. After years of testing, these potential hazards will reduce their useful life. Therefore, it is recommended that the capacitor withstand voltage specified by the customer should be no more than 2 times. Moreover, in this case, in order to better guarantee the customer's use, the capacitor manufacturer has to perform internal control more than 2 times, but these margins are also guaranteed by increasing the thickness of the medium. If the customer gives more than 2 times or even 3 times the index, then we still have to tighten, so unrestricted addition, it is a kind of damage to the capacitor, and it is also a kind of damage to the lighting products, even if there is no production or testing process. Reflected, but it has hidden hidden dangers for future users, which is unfavorable for capacitor suppliers, lighting manufacturers and consumers, because our common goal is to meet consumer use.