ABB UAD149 After sales service is provided for the control card of the power supply device

Description

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Supposing the need to change from 0.8 to 0.93 the power factor of a threephase installation (Ur
= 400 V) which absorbs an average power of 300 kW.
From Table 2, at the intersection of the column corresponding to the final
power factor (0.93), and the row corresponding to the starting power factor
(0.8), the value of Kc
(0.355) can be read. The reactive power Qc
which must
be generated locally shall be:
Qc
= Kc
. P = 0.355 . 300 = 106.5 Kvar
Due to the effect of power factor correction, the current absorbed decreases
from 540 A to 460 A (a reduction of approximately 15%).
Characteristics of power factor correction capacitor banks
The most economical means of increasing the power factor, especially for an
installation which already exists, is installing capacitors.
Capacitors have the following advantages:
– low cost compared with synchronous compensators and electronic power
converters;
– ease of installation and maintenance;
– reduced losses (less than 0.5 W/kvar in low voltage);
– the possibility of covering a wide range of powers and different load profiles,
simply supplying in parallel different combinations of components, each with
a relatively small power.
The disadvantages are sensitivity to overvoltages and to the presence of nonlinear loads.
The Standards applicable to power factor correction capacitors are as
follows:
– IEC 60831-1 “Shunt power capacitors of the self-healing type for a.c.
systems having a rated voltage up to and including 1000 V – Part 1: General
– Performance, testing and rating – Safety requirements – Guide for installation
and operation”;
– IEC 60931-1 “Shunt power capacitors of the non-self-healing type for a.c.
systems having a rated voltage up to and including 1000 V – Part 1: GeneralPerformance, testing and rating – Safety requirements – Guide for installation
and operation”.