Feature: Components
V
Reactors and filters – the essential parts to reliable variable frequency drives
By M. S. Bharath, power quality engineer, and G Prashanth, Product Management Engineer, EMI Solutions, Bangalore, India
ariable frequency drives (VFD) are one of the most common types of drive used today, widely used to control pumps and compressors. To ensure their reliable operation, a key task is to protect them from power surges and transients. Tere are several sub-components within
the VFD and motor that are sensitive to irregularities in power, including voltage spikes, line distortions, current surges and harmonics. To regulate distortions, different types of reactors and filters are
used, including: • Line reactors; • Dv/Dt reactors; • Harmonic filters; • Dv/Dt filters; • Sine filters. By using these devices either separately or combined, the service
life of a motor and VFD can be increased. In turn this improves system performance and drive reliability. Depending on the output voltage of the motor drive, the cable
length and layout are also important, since they influence voltage spikes. Te appropriate reactor or filter chosen for the specific cable length can help mitigate this issue.
Reactors and filters Reactors are basically inductors - electromagnetic devices that consist of steel core electrical-grade laminations and copper inductor coils. Te coil forms a magnetic field as current flows through it, which limits the rate of rise of current. Depending on whether they are installed at the input or output side of the VFD, they are known as line or load reactors. Filters, on the other hand, are a combination of inductance and
capacitance. Tey are electromagnetic devices consisting of passive L-C circuits that offer protection from harmonic disturbances and transients. Tey offer longer range protection compared to reactors.
Figure 1: Different types of reactors and filters
46 September 2024
www.electronicsworld.co.uk
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