6 Frequently Asked Questions About AFDs/VFDs
Centro, Inc. offers a selection of Danfoss adjustable frequency drives (AFDs), also referred to as variable frequency drives (VFDs), that are rugged in design, optimize existing or limited space, deliver energy savings, and allow for long cable runs without the use of ancillary equipment.
Cost Lever | What It Solves | What to Measure | How to Validate |
Space Optimization | Avoids switch room expansion; allows for increased lineup density | Drive frame dimensions, clearances, access, lineup density | Verify clearances/service access; check for thermal hot spots |
Back-Channel Cooling
| Reduces switch room HVAC load | Room HVAC margin, ambient temps, drive losses, airflow/ducting, feasibility | Track temperature trends; compare HVAC run-time pre/post |
Long Cable Runs | Avoids add-on components when permitted | Cable length/type, grounding/shielding, switching frequency, EMC needs | Fault logs, EMI symptoms, motor temperatures |
Rugged Design | Reduces failure in dust/heat | Ambient/derating, dust exposure, enclosure strategy | 30- to 90-day inspection; temperature and fault trending |
The following are the most frequently asked questions we receive, along with a few tips on how Centro can guide you to the right system.
1. Is There a Difference Between an AFD and a VFD?
AFDs and VFDs are different terms for the same device and are typically used interchangeably. Both optimize motor performance by precisely controlling speed and torque, improving energy efficiency, and extending equipment life.
2. How Do Danfoss Drives Affect Space Optimization?
Danfoss’s VLT and VACON series drives are highly compact, designed for long motor cables, and require no additional options, making them ideal for small switch rooms and reducing infrastructure costs by allowing companies to utilize or intentionally design smaller electrical spaces.
3. How Does Back-Channel Cooling Reduce Switch Room HVAC Requirements?
Specifically, Danfoss VLT and VACON liquid-cooled drives remove nearly 85% of power loss through the heatsink, leaving only 15% to be dissipated in the switch room. The unique design of Danfoss VLT drives owes to the separation created using an IP54 enclosure that makes it seamless to duct outside air in and out through the back-channel air path.
4. Do I Need an Output Filter for Long Motor Cable Runs?
Sometimes. Whether you need a dV/dt or sine filter depends on cable length, voltage, switching frequency, motor insulation, and the specific drive design.
Danfoss VLT and VACON AC drives, however, support cable lengths of 500 ft. (screened) and 1,000 ft. (unscreened) without requiring output filters. Danfoss HVAC drives feature built-in radio frequency interference (RFI) filters that ensure EMC compliance and reliable performance across the entire electrical installation.
Danfoss HVAC drives feature built-in radio frequency interference (RFI) filters that ensure EMC compliance and reliable performance across the entire electrical installation.
5. What Information Does Centro Need to Help Me Select the Right Drive?
If you want to select a drive that reduces total installed cost without creating commissioning headaches, you must first start with the right inputs. See the table below for examples.
Specification Needed | Example | Why It Matters |
Motor Nameplate | 50 HP, 480 V, 60 Hz, 1,770 RPM, FLA | Drive sizing, protection, thermal margin |
Load Type/Duty | Fan (variable torque), 24/7 | Energy savings potential, tuning approach |
Cable Length, Type | 600-ft. shielded VFD cable in tray | Cable length limits, EMI risk, output filter needs |
Environment | 45° C ambient, heavy dust, NEMA 12 | Derating, enclosure choice, reliability strategy |
Power System | Available fault current, transformer size | SCCR, coordination, harmonics considerations |
Controls/Comms Needs | Ethernet/IP, 4-20mA, bypass required | Integration complexity and panel layout impact |
With this information, Centro can recommend a Danfoss VLT or VACON configuration quickly and align it with your site conditions and constraints.
Reach out to connect with Centro’s product experts to get started.
6. Will a Drive Always Reduce Energy Costs?
Not always. AFDs are energy savers for variable-speed applications, especially variable torque loads. But they're not a universal solution. Analyze your specific application's speed requirements and load profile before assuming you'll see savings.
How Centro Can Help
Ready to find the right Danfoss AFD? Reach out to connect with one of Centro’s technology experts, who can provide application-specific guidance.
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