Going the Distance: SineWave Filter Applications

12/20/22  |  Scott Savage, Rexel Technical Consultant

This post is part III of our In and Out Trilogy:
Read Part I here
Read Part II here

Imagine the motor of your operation is so far away you need a vehicle to measure the distance. You are concerned about the cost of the wire and the voltage drop from one end to the other. You want to size the wire to handle the current, but not oversize the motor, which will drive the cost up. You are so careful with the details – type of cable, length, and sizing.

The motor is rated for MG1 and is the best you can get for voltage spiking, the cabling is VFD cable, and you are feeling this application. You have made all the right decisions and have slain the dragon – or have you?

You have heard of all the sales pitches on “gadgets” and “extras” – All those scare tactics of long lead lengths and motors. Everyone wants to sell you that extra gadget that all the technical nerds are going to question you on – “why did you fall for that?” – and are the same critics who will denounce your design when the motors are failing thousands of feet away. Some will say “even I knew better than that” after googling the topic and acting like an expert. Let’s eliminate both scenarios and you can have them google this blog.

The SineWave filter can be added at any time with no worries. Just have available space, time, and money. When you have more than 1,000 feet of motor cable you must add the filter. The waveform is exactly what you would get from the utility on the output of the drive.

First, Let’s Get a Few Things Straight

• VFD cable is excellent for common mode noise (not required with SineWave filters)
• MG1 motors are standard nowadays and should be used in long-length applications
• Reflected wave is a product of motor lead lengths that exceed 150 feet and beyond depending on the style of AC drive you use, the voltage rating of the motor windings you have, and the voltage of your distribution system (480V and 600V)
• 240VAC systems are not a factor because the voltage is too low to damage the motor windings
• dv/dt filters are good for 1,000 feet or less
• dv/dt filters do not reformulate the output waveform of the drive
• SineWave filters operate between 1,000 - 15,000 feet

Choices on the Output of an AC Drive:

• No output protection between the drive and motor
• Line reactor only (L component inductive only)
• dv/dt filter (LR component inductive and resistive) < 1,000 feet
• SineWave Filter (LRC component inductive, resistive, and capacitive) >1000 feet SineWave filters are a great choice for multiple motor applications.

Wire Types Using SineWave Filter

• Avoid Thermoplastic High Heat Nylon (THHN) wire. If it is already installed the SWF will provide a smoother waveform than an AC drive and can still be used. Please keep in mind that certain SineWave filters do not completely eliminate the common mode noise component (Nexis product does).
• At a minimum, cables should be XHHN or XHHW (water) cross-linked polyethylene
• SineWave filters prior to the installation of VFD-style cable should be considered to reduce common noise, which can cause bearing frosting and fluting in motor bearings. Installation of cable can be found in Rockwell publication DRIVES-IN001. Please note that cabling is not effective unless proper grounding is followed in this document.
• VFD cable connections can be viewed here.

Advantage SineWave Technology in Review

• Reduce motor heating through the reduction of high frequencies
• Reduce motor insulation stress through the reduction of motor peak voltages
• Reduce audio sound/noise between a drive and motor
• Reduce common mode current
• Can allow longer motor lead length between the drive and motor (eliminate reflective wave)

TRANSCOIL MOTOR SHIELD

MTE Corporation GUARDIAN

MTE Corporation Microdrive Filter

Specs:

• - 480V
• - 1HP to 15HP (2-22A)
• - 4 - 8kHZ switching frequency
• - Max 5% voltage distortion
• - >90% common mode attenuation
• - Provisions for PF 520 series VFDs

Shown above are two manufacturers – Transcoil (TCI) and MTE Corporation. Both specialize in power-quality products and make SineWave filters.

Additional Features with SineWave Technology

• - SineWave filters attenuate and sometimes eliminate all common noise
• - SineWave filters mitigate reflected wave and poor waveform quality to the motor
• - Handle the total distance of multiple motor applications (add each motor lead length)

PowerFlex 750 Parameter Settings (Rockwell Knowledgebase QA6467)

PowerFlex 700 parameter settings (Rockwell Knowledgebase QA17707)