How to Maintain a Variable Frequency Drive?
Many utilities are now offering rebates for the installation of VFD’s or retro-fitting existing equipment with variable frequency drives. Contact your local utility or search VFD rebate or go to the DSIRE website, a comprehensive source of information on state, local, utility and federal incentives and policies that promote renewable energy and energy efficiency.
Joliet Technologies has partnered with Electrical Solutions Network (ESN), in our effects to promote energy efficiency through the use of variable speed drives.
Nationwide energy reduction incentives.
How To Maintain a VFD
By: Dave Polka
Do you know how to maintain Variable Frequency Drives (VFDs)? Doing so is easier than you might think. By integrating some simple, logical steps into your preventative maintenance program, you can ensure your drives provide many years of trouble-free service. Before looking at those steps, let’s quickly review what a VFD is and how it works.
A Quick Overview
A VFD controls the speed, torque and direction of an AC Induction motor. It takes fixed voltage and frequency AC input and converts it to a variable voltage and frequency AC output. See Training Note “What is a VFD?” for a more detailed description of VFD concepts and operating principles. In very small VFDs, a single power pack unit may contain the converter and inverter.
Fairly involved control circuitry coordinates the switching of power devices, typically through a control board that dictates the firing of power components in the proper sequence. A microprocessor or Digital Signal Processor (DSP) meets all the internal logic and decision requirements.
From this description, you can see a VFD is basically a computer and power supply. And the same safety and equipment precautions you’d apply to a computer and to a power supply apply here. VFD maintenance requirements fall into three basic categories:
- keep it clean;
- keep it dry; and
- keep the connections tight.
Let’s look at each of these.
Keep it Clean
Most VFDs fall into the NEMA 1 category (side vents for cooling airflow) or NEMA 12 category (sealed, dust-tight enclosure). Drives that fall in the NEMA 1 category are susceptible to dust contamination. Dust on VFD hardware can cause a lack of airflow, resulting in diminished performance from heat sinks and circulating fans (Photo 1).