• • • EDITOR’S CHOICE • • • Line Reactors for vfd Harmonic Filters for vfd
role is to protect the motor by regulating drive output voltage and preventing spikes to the motor. • Limits the peak voltage and protects the motor insulation windings from premature wear and tear.
• Low pass filters with low inductance, limited reduction in the control dynamic. • Minimises interference propagation towards neighbouring equipment or lines. • Output current ripple is lower, but the voltage is still PWM pulse pattern shaped. • Have a longer range of motor protection compared to load reactors.
Fig 4 – Harmonic Filters for vfd. Fig 2 – Line Reactors for vfd.
Also known as input reactors as they are installed at the input side of the VFD and their primary role is to protect the VFD from incoming line voltage distortion such as spikes and surges. • Switching transients can peak at over 1000 volts. The inductive characteristics of the Line Reactor restricts this sudden surge and eliminates nuisance safety tripping.
• By limiting the inrush current to the rectifier in the VFD, the line reactor can minimise harmonic distortions.
Commonly used in Motor Drives, Automotive, Industrial Automation and power Quality applications.
Dv/Dt Reactors
Two types of harmonic filters are available – passive harmonic filters and active harmonic filters. Passive harmonic filters utilise components such as inductors, capacitors, and power resistors to filter noise on single variable speed drives before electricity reaches equipment with an electromagnetic field. • They are L-C combination electromagnetic devices installed at the input side of the VFD. • Their primary role is to protect the VFD and regen unit from line side disturbances and transients.
Active harmonic filters can work with many variable speed drives and actively reduce noise by constantly monitoring electricity and injecting currents to mitigate harmonics.
• Designed in a way that the filter passes current at the fundamental frequency but blocks current at higher frequencies.
• Provide excellent harmonic mitigation performance and helps to achieve IEEE 519 standard.
Common applications include Motor Drives, Automotives, Industrial Automation and power Quality applications. Dv/Dt filters are L-C combination
electromagnetic devices installed at the output side of the VFD, before the motor. Their primary
Sine wave filters for vfd Sine wave filters for vfd are L-C combination electromagnetic devices installed at the output side of the VFD, before the motor. • Sinusoidal output filters with high inductance and capacitance, helps to optimise the output signal.
• Protects the motor by regulating the PWM wave distortions coming out of the drive so that it resembles an AC sine wave.
• They help to minimise motor drive losses by reducing the high frequency leakage currents, reducing bearing currents and eliminating the pulse reflections in the motor cable.
Common applications include Motor drives with long motor cable, motor drives with multiple motors in parallel and retrofitting installations. The table below summarises the features and functions of the various reactors and filters discussed above for quick reference.
EMI Solutions (EMIS) has been designing and manufacturing EMI filters for more than 40 years and is a global source for efficient EMI and EMC solutions across all industries, applications and the frequency spectrum. With a robust global supply footprint across eight industry segments, EMIS is continuously investing in technology and skills to deliver its promise of efficiency with seamless customer support.
Device
Summary of Reactors & Filters for VFD and motor protection Position
Purpose Line Reactor (also called Input Reactor)
INDUCTANCE ONLY Load Reactor
(also called Dv/Dt Reactor Fig 3 – Dv/Dt reactors.
Sometimes referred to as load reactors because they are installed at the output side of the VFD, before the motor. The term Dv/Dt Reactor is used because they provide efficient reduction of high output voltage dv/dt from IGBT motor drives. • The high design inductance of the Dv/Dt reactor will smoothen the rough voltage spikes and slow down the distortion as the voltage is provided to the motor.
• They are effective in protection of motor coil insulation from premature aging and destruction. Common applications include Servo drives, close loop vector drives, motor drives with short motor cables, Robotics and Industrial Automation.
electricalengineeringmagazine.co.uk
or Output Reactor) INDUCTANCE ONLY Harmonic Filter
INDUCTANCE & CAPACITANCE Dv/Dt Filter
INDUCTANCE & CAPACITANCE Sine Filter
INDUCTANCE & CAPACITANCE ELECTRICAL ENGINEERING • OCTOBER 2024 11 Before the VFD Protects the VFD from incoming line voltage distortion such as spikes and surges
Between the Protects the motor by regulating drive VFD and motor output voltage
Before the VFD Protects the VFD and regen unit from line side disturbances and transients
Between the Protects the motor by regulating drive output VFD and motor voltage and preventing spikes to the motor
Between the Protects the motor by regulating the PWM VFD and motor wave distortions coming out of the drive so that it resembles an AC sine wave
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