VTF – SWF SERIES
PASSIVE FILTERS FOR MOTOR PROTECTION

PROTECTED AC MOTORS

PASSIVE FILTERS FOR MOTOR PROTECTION
VTF – SWF SERIES

VTF
IREM VTF series dV/dt Filters extend the service life of motor windings, protect the motor against voltage peaks, and enhance performance in three-phase asynchronous motor drives controlled by inverters. Typical applications include loads in air conditioning systems, water treatment plants, the oil sector, and industrial automation processes in general, for cable lengths up to 250 m.

SWF
IREM SWF series Sinusoidal Filters provide a sinusoidal voltage at the motor terminals. Installing the sinusoidal fi lter between the VFD power source and the motor attenuates the amplitude of the square-wave pulse modulated by the VFD, converting it into an almost perfect sinusoidal waveform.
The typical applications of SWF sinusoidal fi lters are the same as those of VTF filters but with enhanced performance for cable lengths exceeding 250 m or in cases wher eliminating bearing currents is desired to extend motor lifespan.

IREM PROPOSAL

DV/DT FILTERS (VTF)

With this type of fi lter, the voltage applied to the motor remains pulsed, but the rise time and peak voltage are signifi cantly reduced, resulting in the following advantages:

Partial reduction of bearing currents;
Reduction of electromagnetic interference propagation towards cables and the surrounding environment;
Elimination of refl ections on the motor cable, improving EMC performance;
Ensures compliance with the requirements of the IEC60034-17 and NEMA-MG1 standards for general-purpose motors with power supply lines up to 250m.

SINUSOIDAL FILTERS (SWF)

This type of fi lter eliminates the effects of PWM by recreating a perfect sinusoidal waveform, providing the following benefits:

Reduction of thermal losses due to hysteresis;
Elimination of acoustic noise caused by magnetostriction;
Reduction of thermal losses;
Reduction of bearing currents caused by leakage currents;
Elimination of refl ections on the motor cable, improving EMC performance;
Ensures compliance with the requirements of IEC 60034-17 and NEMA MG1 standards for general-purpose motors with power supply lines exceeding 250 meters.

DRIVE-INDUCED DISTURBANCES IN MOTOR POWER SUPPLY

Passive filters for motor protection - applications

AC motor drives (VFDs) are widely used to control motor speed, effectively adapting it to process requirements, improving machine automation, and saving energy.

However, after installing power inverters, many users have reported frequent motor failures. These failures are often due to the absence of output filters from the VFD, especially when the motor is located far from the drive.
Additional filters help balance the eect of cable capacitance and protect the motor from potential damage. The use of output filters becomes essential to safeguard the motor when a VFD is installed on a motor that was not specifically designed for this application, such as in retrofit cases

Variable speed drives use a Pulse Width Modulation (PWM) technique to control the output voltage and motor supply frequency.
The voltage supplying the inverter-connected motor is generated using PWM, resulting in a sequence of pulses with varying duration.
The high rate of voltage increase in these pulses (dV/dt) can cause significant leakage currents through the motor power cables, as well as between the motor windings and between the windings and the motor housing.
Additionally, the high dV/dt, combined with the intrinsic inductance of the connection cables, generates high voltage peaks that stress the insulation of the motor windings

Reflections occur due to impedance mismatch between the source and the load, which in turn results from improper installations, incorrect component selection, or equipment degradation over time.
Defects in the insulation of motor windings can lead to unplanned downtime, which is not easily resolved

The use of variable speed drives affects motors by causing:

Electrical stress on the stator winding insulation system due to high-frequency switching (High Frequency Switching);
Electrical stress on the insulation system due to the steep voltage rise time (Short Rise Time);
Electrical stress on the insulation system due to transient overvoltages (Transient Voltage Spike);
Electrical stress on the insulation system due to reflected wave voltage (Reflected Wave Voltage);
Electrical stress on connection systems and motor terminals;

Thermal stress on the insulation system due to increased current in the windings caused by the square wave signal (Additional Heat);
EMC emissions, which can severely impact the proper operation of loads powered by lines adjacent to the motor’s VFD supply line;
Stress on motor bearings;
Additional acoustic discomfort from the motor’s magnetic core.