FEATURE Drives, controls & motors
Reactors and
filters for reliable VFDs
reliable VFDs
By M. S. Bharath, Power Quality Engineer, and G Prashanth, Product Management Engineer, EMI Solutions, Bangalore, India
V
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. There 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.
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 mitigate this issue.
Reactors are basically inductors - electromagnetic devices that consist of steel core electrical-grade laminations and copper inductor coils. The coil forms a magnetic 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. They are electromagnetic devices consisting
14 September 2024 | Automation
from harmonic disturbances and transients. to reactors. in motor drives, automotive, industrial automation and power quality applications. of the VFD, they are also known as “input reactors”. Their primary role is to protect the drive from incoming line voltage distortion, such as spikes and surges.
so the inductive characteristics of the line reactor restrict these sudden surges and eliminate nuisance safety tripping. Also, by limiting the inrush current to
minimise harmonic distortions.
Dv/Dt reactors
reactors include servo drives, closed loop vector drives, motor drives with short motor cables, robotics and industrial automation. They are installed at the output side of the VFD, before the motor, hence their other Dt reactor” is used because they provide
Dt reactor will smoothen the rough voltage spikes and reduce distortions as the voltage is applied to the motor. motor coil insulation from premature ageing and destruction.
use inductors, capacitors and power resistors
many variable speed drives and actively reduce noise by constantly monitoring electricity and injecting currents to mitigate harmonics. They are designed to pass current at the fundamental frequency but mitigation, they help systems meet the IEEE
installed at the output side of the VFD, before the motor. Their primary role is to protect the motor by regulating the drive output voltage, and prevent spikes from reaching the motor. Among their primary
motor insulation windings from premature the voltage is still pulse-width modulated load reactors.
installed at the output side of the VFD, before the motor. Their high inductance and capacitance and sinusoidal output help optimise the output signal. These devices protect the motor by regulating the motor drive losses by reducing high frequency leakage- and bearing-currents and cable.
automationmagazine.co.uk
Reactors and filters for
Fig 1: With a direct drive, the motor is directly coupled to its load. This connection removes the inertia resulting from power transmission components
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