What support products does it take to maximize the impact of using VFDs and VSDs? - Part 1
limitations for industrial, scientific, and medical equipment, and IEC/EN 61800-3, which relates specifically to adjustable speed drives. VFDs/VSDs are available with and without integrated line filters. If they have a filter, it may be Class A or Class B. Depending on the environment and installation factors like cabling lengths, even a drive with an integrated filter may require additional filtering. A drive rated for operation in Class A environments can also be used in Class B environments with the addition of an optional filter. IEC/EN 61800-3 defines EMC requirements based on Environments and Categories. Residential buildings are defined as the First Environment, and industrial installations connected to the medium-voltage distribution network through their transformers are the Second Environment. The four Categories defined in EN 61800-3 include: ■ C1 for drive systems for rated voltages < 1000 V for unlimited use in the first environment ■ C2 for stationary drive systems for rated voltages < 1000 V for use in the second environment and possible use in the first environment
overload is detected, the drive is turned off. Turning off the braking function only could result in serious damage to the drive. Protection on the drive input Line reactors and filters on the drive input limit low-frequency harmonics and high-frequency EMI, respectively (Figure 4). Line reactors help reduce harmonic distortion of the AC input power caused by the drive circuitry. They can be especially useful in applications that must meet the requirements of IEEE-519, “Harmonic Control in Power Systems.” Line reactors also smooth out disturbances on the mains power like surges, spikes and transients, increasing operating reliability, and preventing overvoltage shutdowns. Examples of line reactors include the DV0P228 2 mH inductor rated for 8 A that’s part of the Minas family of three-phase drives and accessories
from Panasonic and Siemens’ 6SL32030CE132AA0 2.5 mH
inductor rated for drives up to 1.1 kW that draw up to 4 A of input current and operate from 3-phase 380 V AC -10% to 480 V AC +10% power.
Line filters
Line filters are required to support electromagnetic compatibility (EMC) and provide EMI protection in most applications. Depending on the specific environment, two classifications of EMI filters, Class A and Class B, are used in industrial
and commercial (building) environments, respectively.
Class B demands a higher level of filtering than Class A because commercial environments (offices, administration, etc.) generally include electronic systems that are more sensitive to EMI. The relevant EMC standards include EN 55011, which details emissions
Figure 4: Line filters limit high-frequency EMC, while line reactors limit low- frequency harmonics. (Image source: Siemens)
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