April 25, 2022

Hammond Power Solutions (HPS) has a new addition to their line of power quality products – HPS Centurion D1 dV/dT Filter. The HPS Centurion D1 is designed for use between variable frequency drives (VFD’s) and motors when long lead lengths are used. It combines an inductor and parallel resistor network to mitigate both high frequency components and voltage spikes between the VFD and motor.

These filters provide protection for both the motor and cables that power it, and are typically used when the cable length exceeds a value that can lead to high voltage levels caused by reflected wave phenomena. dV/dT filters provide protection to the motor by slowing down the rate of voltage increase and minimizes the damaging peak voltages that occur within the motor’s windings and terminals.

The HPS Centurion™ D1 dV/dT filter combines an inductor and parallel resistor network to mitigate both high frequency components and voltage spikes between the VFD and motor. The D1 can mitigate the effects of reflected wave voltages greater than what a reactor alone can accomplish. The D1 filter provides protection to the motor by slowing down the rate of voltage increase and minimizes the damaging peak voltages that occur within the motor’s windings and along the length of cables feeding the motor.

Operation Principle

The term “dV/dT” refers to the change in voltage over change in time. With regards to VFD’s, dV/dT is explained as the rapid change in voltage at the beginning or end of the square wave pulses that make up the pulse width modulated (PWM) output of a VFD that powers the motor. As the square wave pulses travel the electrical cable to the motor, the differences in impedance between the cable and motor windings cause some energy in the pulse to be “reflected”. In applications where the distance between the motor and VFD is long, the voltage of two pulses can combine in the cable or motor windings. This creates a high voltage condition of twice or more the VFD’s DC bus voltage. Long lead length motor applications can experience peak voltages up to 1600V in a 480V system and up to 2100V in a 600V system. These high peak voltages will cause motor winding failures and premature motor insulation failure resulting in down time and lost revenue.

Typical examples of HPS Centurion D1 dV/dT filter applications include oil and gas pumps, wastewater treatment plants, HVAC systems, pulp and paper, and irrigation fields.

Notes:

¹VFD rated cable recommended
²Maximum motor cable size to achieve 5% voltage drop (including 2% from the filter)
Maximum lead length and carrier frequency can vary depending on motor cable type

To learn more about HPS’s new Centurion D1 dV/dT Filter, download the product catalog here or visit the Hammond Power Solutions website by clicking here