Harmonic Filters
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Matrix Filters may be used for phase controlled DC drive applications to improve power factor and reduce line harmonics. Application to DC drives is similar to AC drives with a few important differences in filter performance and the selection of the appropriate filter rating. The following paragraphs cover these differences. Matrix Filter Selection Selection of the proper Matrix Filter rating for a DC drive is based on the horsepower and voltage rating of the drive. Applications for DC motors rated at 500 volts or higher may use a 480 VAC filter rated at the same horsepower as the DC drive provided the motor efficiency is a minimum of 85%. DC motors with lower efficiencies will typically draw higher ac input current and therefore a Matrix Filter rated for higher horsepower may be required. The following equation should be used to select the correct filter rating: Matrix Filter HP = DC Drive HP x 85% DC motor efficiency If the calculated filter horsepower falls between two standard horsepower ratings, the next larger filter rating should be selected. This will insure that the drive may be used at full rated horsepower without overheating the Matrix Filter components. Do not use this equation to downsize the Matrix Filter when motor efficiencies are greater than 85%. The same type of scaling is necessary for motors with armature voltage ratings less than 500 volts. To select a Matrix Filter for a DC drive, when the motor armature voltage is less than 500 volts use the following equation. Matrix Filter HP = DC Drive HP x 500Volts Rated Armature Voltage If the calculated filter horsepower falls between two standard horsepower ratings, the next larger filter rating should be selected. > Page 1 of 4 size="-1">

Matrix Filter Performance Matrix Filters are suitable for use with DC drives and other phase controlled rectifier applications, but harmonic performance will vary based upon controller output voltage (speed) and output current (load). While it is not possible to specify guaranteed levels of harmonic distortion for Matrix Filters used with phase controlled SCR applications, Matrix filters are extremely effective at solving harmonics problems associated with DC Drives and other six-pulse phase controlled rectifiers. The performance of the Matrix Filter with a DC drive differs from that with...