Reflective Wave phenomena in VFD applications

Reflective Wave phenomena in VFD applications

Below is common practice when reflective wave phenomena when application of three phase motors are utilized in combination with VFD's (AC Drives).  This is not "all-inclusive" summary, but a practical approach with consideration to machine reliability and project costs.  LSE or its partners as the manufacture of AC Drive product is affirming that the below application summary is not far-reaching or as providing any obligation/ liability to remedy. 

  1. No cost material solution is to lower the drive output “Fc” (Carrier Frequency).  LSE has also a drive Low Leakage setting to minimize PWM degradation.   However, audible “noise” emitting from the AC Motor may be a nuisance to humans at the drives setting to a lower “Fc”.  But at a great determination for the eventual AC Motor destructive issues by keeping the Drive’s “Fc” at much higher frequency. 
  2. Depending onto numerous application/ installation variables, project expense typically incrementally increases in material/ labor costs as to all of the solutions listed below, the first is typical at the lowest material/ installation cost:
    1. Adding Motor brush ring (inexpensive) but device itself has low MTBF.  Perhaps Inductive Ring technology that is just as inexpensive but is Long Lasting/ Durable/ Low Maintenance product.
    2. utilization of Inductive Ring placed on AC Motor frame.  
    3. Adding drive output Load Reactor.
    4. Adding drive output DvDt Filter.
    5. Adding drive output Sine Wave Filter.
    6. One of the above, and/ or utilizing VFD Cable.
    7. Installing Ceramic Bearings on AC Motor (depending on application, could be installed on both ends -​ typically 100HP or more). 

Some projects have a mixture of the above solutions listed. 

EXAMPLE:

On a typical Extruder application at 500HP would have employed AC Drive Output Load Rector 3%, VFD Cable and with the AC Motor having Ceramic Bearings installed on both ends of motor shaft.  Noting at this KW, machine/ process is costly in terms of down-time if a failure to exist, so that process/ machine reliability is increased with the above stated solution.