Have you ever wondered what all those numbers and letters on the nameplate of a three-phase tubular capacitor mean?
Although it may seem like a puzzle at first, in this article I will explain in a simple way how to interpret all this information.
Understanding its nameplate will help you to correctly assemble, install or repair an LV capacitor bank.
Power Capacitor Nameplate: Deciphering the Details
On the nameplate of a capacitor, you will find essential information that will allow you to understand its specifications and performance. Here are the key elements:
1 – Identification of the model and place of manufacture
The nameplate begins by providing you with the model identification of the three-phase tubular capacitor. This information allows you to differentiate between different types and sizes of capacitors to suit your specific needs.
In addition, the place of manufacture is also indicated, which may be relevant for some customers in terms of quality and origin preferences.
2 – Rated power and voltage
One of the most critical aspects is to understand what is the capacitive reactive power of the capacitor.
El condensador tiene una potencia nominal de diseño a una tensión y frecuencia determinadas. Lo que encontraremos en la etiqueta de los condensadores de ZEZ Silko es una tabla donde aparece la potencia y tensión nominal resaltado en negrita, en la imagen son 440 V y 10 kvar, pero se incluyen los valores de potencia que ofrecerá el condensador cuando la tensión del sistema eléctrico es inferior a la nominal.
Este condensador al funcionar a 400 V nos aportará 8,3 kvar. Si quieres saber por qué, te lo explicamos en este artículo técnico. [enlace a próximo artículo]
3- Element capacity and tolerance
Here you will find the capacity data of the capacitive elements that make up the tubular capacitor.
In the case of the example, this capacitor is indicating that it has 3 capacitive elements of 54.8 μF. Do not confuse the capacity measured between terminals in case of maintenance.
And next to is the tolerance according to the power capacitor standard, which in this case is from -5% to +10%.
4- Internal connection of the pòwer capacitor
The capacitor’s nameplate must indicate what its internal connection is like. The most common are:
‘D’ indicates a triangle connection
‘Y’ indicates a star connection
In the case of the example capacitor we clearly see how the connection is in a triangle symbolized with a ‘D’.
5- Ambient temperature range
In accordance with the international standard for low voltage capacitors, IEC 60831-1, a lower and upper temperature range must be established, which is established by the manufacturer.
The lower limit of the capacitor in the example indicates that it is -40º C.
Now, the upper limit is somewhat more difficult to understand since according to the norm it is symbolized by a letter, which establishes upper limits: maximum, daily average and annual average. I leave you a table where you have those correspondences:
Categories A and B would be missing from this table, but they are not frequent.
The ZEZ Silko capacitors sold by Vector can reach a maximum temperature of 60ºC, higher than what is required by standard, providing greater robustness.
6 – Internal discharge resistance and self-regenerative system and self-regenerative system
On the right side we will find two symbols, just below the internal connection symbol.
This symbol indicates that the power capacitor is constructed from a self-healing system of the dielectric that forms the capacitor. If a small perforation occurs in the dielectric of the capacitive element, it evaporates part of the metallized layer to ‘heal’ and remain operational, although somewhat reducing its benefits.
This symbol indicates that the capacitor has an internal discharge resistance.
Discharge time and safe residual voltage
The safe residual voltage and the discharge time at that maintenance or reconnection of the capacitor after being disconnected.
These values tell you how long you should wait after disconnecting the capacitor to ensure that the residual voltage has decreased to safe levels before handling it.
The example shows that a residual voltage of 50 V is reached after 1 minute.
8 – Insulation level
It consists of two digits that indicate the insulation level in case the terminals are insulated from the casing.
The first digit indicates the test value at mains frequency and the second the peak value at lighting impulse test.
9- Degree of protection and filling
The capacitor protection rating (IP 20) is suitable for most applications where the capacitors are located within the capacitor bank. In some cases caps may be available to increase the degree of protection of the terminal block.
Along with the degree of protection, the type of filling or impregnant used is indicated. ZEZ Silko LV power capacitors are always dry (without synthetic insulating oils). They can be with nitrogen (inert gas that prevents contact of oxygen and humidity with the conductive metallization) or with resin.
10 – Overpressure protection system
Tubular capacitors have an overpressure fuse protection system, which is relevant to avoid damage in the event of overload and significant perforation of the dielectric, causing an accumulation of gasses inside the capacitor.
This buildup pushes the top cap, disconnecting the connections with the capacitive elements. By lifting the cover, a minimum space of 20 mm must be left at the top of the condenser and not prevent the protection system from operating.
11- Rule and warning
Finally we find the standard applicable to low voltage power capacitors, IEC 60831-1, as well as the recommendation of a waiting time of 5 minutes after disconnecting the power supply before being manipulated.
With this information, you are to correctly interpret the nameplate of a three-phase power capacitor.
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