DELTA and WYE 3-Phase EMI Power Line Filters
In general, Industrial applications (induction heaters, inverters, machinery, etc.) demand high power and therefore, are generally designed for three phase power. Three phase power splits the total power into various phases, thus optimizing the supply generation and distribution as well as the equipment design. A three phase system consist of three current-carrying conductors, or phases, set at the same voltage and frequency and phase-shifted from each other by an angle of 120°. There are two configurations of 3-phase systems, Delta and WYE. Delta systems consist of three phases and WYE systems include a neutral often used to power control and auxiliary circuits.
Three phase EMI power line filters are required to reduce the high frequency harmonic noise created by a system’s power conversion circuits. These circuits utilize high frequency switching techniques and can produce harmonic noise at frequencies into the tens of MHZ. In addition, these circuits produce unbalanced harmonic currents which is not equally divided among the phases, driving currents into the neutral and ground wiring. Three phase EMI filter design must take into account these affects as saturation of the filter’s magnetic circuits can occur reducing filter performance.
The primary difference between a delta and wye three phase EMI power line filter is the addition of a neutral terminal on the wye filter. Therefore, the wye EMI power line filter design must take into account this additional terminal in order to ensure proper filter function and performance. This especially comes into play with the design of the filter’s common-mode inductor. It is critical that the neutral line be incorporated in the common-mode inductor along with the other three phases. In addition, proper winding orientation is critical to ensure proper balancing and cancellation of the existing line current.
Three phase EMI Power Line Filters, as with all EMI filters, are rated according to the maximum voltage and current that the filter can handle without degradation of reliability and quality. In general, the voltage rating is determined by the capacitors used and the current by the inductor design. It is important that all lines of a filter, including the neutral, are designed to handle the maximum current rating of the equipment or system. This is usually determined by the circuit breaker rating protecting the equipment. Typically, a delta distribution will specify the voltage according to the phase-phase voltage (e.g. 480V, 600V, 690V) while a wye system will include the phase to neutral voltage (e.g. 208V/120V, 480V/277V).
At Premier Filters, we offer an extensive line of standard and custom Three phase EMI Power Line Filters. All standard products are rated at 520VAC with unlimited custom capability. Current custom designs have been to 5KVAC and up to 3KA. Call or email to see how Premier can meet your three phase EMI filter requirements on time and on budget.