Electronic potting of variable frequency drives (VFD)

Metering and mixing two-part polyurethane

A variable frequency drive (VFD) is an electronic device that controls the speed of AC induction motors. These drive motors are widely used throughout a wide range of different industries including oil and gas, industrial, power generation, infrastructure, food and beverages, automotive, and many others. These industries often use AC motors where the speed needs to be constantly controlled and varied. The Inverter driver alters the frequency of the drive motor in order to change the speed. Typically, the inverter takes a single-phase electric supply and converts this to a three-phase supply in order to drive the motor. During the production of the inverter drives, the internal components have to be encapsulated with a two-component polyurethane resin. This seals the components, provides heat dissipation and protects them from environmental influences.

Requirements:
For the application, the customer needed a machine that could accurately meter, mix and dispense an air-free material into the inverter by continuous pouring methodology. The previous potting process was laborious as it relied on manual mixing of the resin and this was both problematic & time consuming. The Design & Production Engineers required a system to not only meter, mix & dispense the resin at a specific flow rate, but to also constantly monitor the volumetric mixing ratio whilst pouring. In addition, the A component (Resin) contains a high degree of filler that easily separates during when not being constantly agitated during the metering and mixing process. There were also frequent problems with the hardener component, as it crystallises easily.

Solution:
The new PAR 30 gear pump metering and mixing system from METER MIX speeds up this process significantly. The PAR 30 machine provides a constant pour process together with heating & agitation on the Part A (Resin) reservoir in order to correctly pre-condition the resin. The potting process is now reduced down from >10 minutes to less than 1 minute. In addition, fillers in the material no longer separate. Finally, the two components can be reliably metered and mixed at any time. The result is a high-quality potting compound that optimally protects the component.

The benefits at a glance:

  • Faster production turnaround of parts
  • Higher efficiency and cost-effectiveness
  • Controlled flow rate for filling larger components/shot sizes will minimal turbulence
  • Monitored ratio metering to inspire confidence in correct mixed resin
  • Better control of the materials when in production
  • Cleaner and safer operation

Technical Specifications PAR 30:

  • Bench or floor mounted
  • Bulkfeed system from supply drums
  • Electric agitation for the base resin
  • Heating circuit for the base resin
  • Rotary pump seal for improved handing & processing of Isocyanate material