All Categories ▼

Protecting the VFD and motor from power surges and transients is one of the most critical priorities while maintaining a drive system. There are several sub-components within the VFD and motor which are sensitive to irregularities in power such as voltage spikes, line distortions, current surges or harmonics.

Different types of reactors and filters are employed to regulate these distortions. They are as follows:

Line Reactor

Dv/Dt Reactor

Harmonic Filter

Dv/Dt Filter

Sine Filter

By using these devices either separately or in combination, the service life of the motor and VFD can be increased. It also improves the system performance and reliability of the drive system.

Depending on the output voltage of the motor drive, the cable length and layout are also important factors that influence voltage spikes. The appropriate reactor or filter chosen for the specific cable length can help mitigate this issue.

Filters & Reactors for VFD and Motor Protection

Device	Position	Purpose
Line Reactor (also called Input Reactor or Input Choke )INDUCTANCE ONLY	Before the VFD	Protects the VFD from incoming line voltage distortion such as spikes and surges
Load Reactor (also called Dv/Dt Reactor or Output Reactor or Output Choke)	Between the VFD and motor	Protects the motor by regulating drive output voltage
Harmonic Filter INDUCTANCE & CAPACITANCE	Before the VFD	Protects the VFD and regen unit from line side disturbances and transients
Dv/Dt Filter INDUCTANCE & CAPACITANCE	Between the VFD and motor	Protects the motor by regulating drive output voltage and preventing spikes to the motor
Sinewave Filter INDUCTANCE & CAPACITANCE	Between the VFD and motor	Protects the motor by regulating the PWM wave distortions coming out of the drive so that it resembles an AC sine wave

Single Phase Line Reactor – PQR (Input Choke)

Voltage Range: 230VAC
Current Range: 2A to 1000A
Operating Frequency: 50Hz

Download Datasheet ↓

Three Phase Line Reactor – PQR (Input Choke)

Voltage Range: 400VAC
Current Range: 2.4A to 1000A
Operating Frequency: 50Hz

Download Datasheet ↓

Three Phase dv/dt Filter – PQDT

Voltage Range: 400VAC
Current Range: 4A to 1100A
Operating Frequency: 50Hz

Download Datasheet ↓

Three Phase Sinewave Filter – PQSW

Voltage Range: 400VAC
Current Range: 2.3A to 1000A
Operating Frequency: 50Hz

Download Datasheet ↓

ThreePhaseReactor–4IMP

Three Phase dv/dt Reactor – PQR (Output Choke)

Voltage Range: 400VAC
Current Range: 4A to 1000A
Phase: Three
Operating Frequency: 50Hz

Download Datasheet ↓

Three Phase Passive Harmonic filter– PQPH

Voltage Range: 3X380-415VAC
Current Range: 1.6A to 1000A
Operating Frequency: 50Hz

Download Datasheet ↓

Line Reactors for VFD

They are also known as input reactors as they are installed at the input side of the VFD.

Their primary role is to protect the VFD from incoming line voltage distortion such as spikes and surges.

Switching transients can peak over 1000 volts. The inductive characteristics of the Line Reactor restricts this sudden surge and eliminates nuisance 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

They are also known as load reactors as they are installed at the output side of the VFD, before the motor.

They derive the name Dv/Dt Reactor 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.

Dv/Dt Filters

They are L-C combination electromagnetic devices installed at the output side of the VFD, before the motor.

Their primary 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.

Minimizes 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.

Sine Wave Filters for VFD

They 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.

Harmonic Filters for VFD

Passive harmonic filters utilize components like 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.

Designed in a way that the filter passes current at the fundamental frequency but blocks current at higher frequencies.

Provides excellent harmonic mitigation performance and helps to achieve IEEE 519 standard.

Common applications include Motor Drives, Automotives, Industrial Automation and power Quality applications.