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6. FILTER DESCRIPTION
The GE Matrix Filter is a low pass filter containing proprietary technology, which makes it particularly useful for harmonic mitigation of adjustable speed drives. Figure 38 shows a block diagram of the filter. Three phase AC power is connected to the input section which contains a three phase AC reactor and circuitry which inhibits oscillation of the filter with the AC power system. The center leg consists of a series reactor and capacitor bank. Because of the capacitor bank the filter operates with leading power factor at all loads, but unlike trap filters the GE Matrix Filter does not produce significant voltage rise at the point of common coupling with the power system. The standard 8% filter output section consists of an AC output reactor.
The 5% filter is comprised of a standard 8% filter plus an additional input reactor.
Matrix filters are suitable for use with AC and DC drives and they can be used in both regenerative and
Filters for variable torque AC drives rated 7.5 Hp and above should be selected for a filter output current rating greater than or equal to the motor current rating. If the motor current rating is not available, use the NEC motor current rating.
Filters for variable torque AC drives rated 2 – 5 Hp should be selected for a filter output current
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rating greater than or equal to 105% of the motor current rating. If the motor current rating is not available, select on the basis of 105% of the NEC motor current rating.
Filters for variable torque AC drives rated less than 1.5 Hp should be selected for an output current rating greater than or equal to 110% of the motor current rating or 110% OF the NEC motor current rating.
For constant torque, AC and DC drive applications operating from six pulse rectifier front ends selected a filter current rating according to application engineering note “Matrix Filter Operation in Constant Torque Applications with Six Pulse Rectifiers” or consult GE engineering. For phase controlled DC drive applications, select filter current rating per application note “Matrix Filter with Phase Controlled DC Drivers.
Where a single filter is used to feed multiple drives, the output current rating of the filter should be selected to equal the total current rating of the individual drives when calculated according to the instructions above.
Because the filter supplies harmonic currents required by the drive, linear loads (such as space heaters, incandescent lighting and AC motors operated across the line) should not be connected to the output of the filter.
44 | May 2003 |