DELTA vs WYE: Three Phase EMI Filters

 Industrial applications predominantly require a high power supply to support high-power equipment (such as induction circuits, inverters, and heating systems). Therefore, high power equipment is generally designed for 3-phase (or poly-phase) AC power. The 3-phase AC power plays a crucial role in the electrical system design as it splits the total power into various phases, and thus optimizes the power system (both generation and distribution) and equipment design. 

3-Phase System 

It consists of three current-carrying conductors (or phases). All three phases (A, B, and C) are set at the same voltage and frequency and phase-shifted from each other by an angle of 120°. It helps to transfer constant power during the electrical cycle. There are two configurations of 3-phase systems, namely Delta and WYE configurations which maintain equal loads. 

3-Phase EMI Filter

High power conversion (such as rectifying) generates higher-order harmonics of different switching frequencies also known as high-frequency noise or EMI (Electromagnetic Interference). This EMI creates a disturbance in the operation of the equipment. To prevent such disturbance, Three Phase EMI filters are used in 3-phase applications as they reduce the amount of EMI. Hence, the 3-phase EMI filter is a vital part of the electrical devices used in heavy-duty industrial applications.


3-phase EMI filter is designed to cater to the strict requirements of EMC regulations for industrial applications. Such regulation specifies the maximum level of noise that is allowed on power lines. There are different requirements for designing a 3-phase EMI filter such as line voltage, size limitation, input current, and required insertion loss. Apart from such requirements, the 3-phase EMI filter configuration also plays a key role in the filter design.

3-Phase EMI Filter Configurations

Delta 3-Phase EMI Filter

Delta 3-phase EMI Filter is used in devices powered by 3-phase delta supply. This filter uses Delta configuration to reduce the EMI. In this configuration, there are three conducting wires and one ground wire. The phase loads (like motor windings) are connected forming a closed circuit. It means one end of the winding is connected to the start end of the other winding forming a triangular shape. This configuration does not incorporate neutral wire, therefore, power is transmitted at a lower cost. Delta system is used for applications that require high starting torque.


In the absence of neutral wire, capacitors of Delta 3-phase EMI filters have to be rated for phase-to-phase (line-to-line) voltage. This causes an increase in size, weight, and cost of the filter. Also, the neutral wire absence allows higher current ratings than WYE configuration and better performance in the same given cubic volume.

How to Design a Delta 3-Phase EMI Filter 

Follow these steps to design a Delta 3-phase EMI Filter

  1. Identify the maximum power needed by the load.

  2. Obtain power per phase. For this, divide the result of step 1 by three.

  3. Divide the result of step 2 by the line-to-line voltage.

  4. Multiply the result of step 3 by the square root of three.

Advantages of Delta Configuration

  • Handle higher currents

  • More efficient

  • Simple protection

  • Used for heavy-duty applications (usually for power generation and transmission)

WYE 3-Phase EMI Filter

WYE 3-phase EMI Filter can be used for filtering switch-mode power conversion devices. This filter is also used in applications requiring a neutral connection. In the WYE configuration, there are three conducting wires, one ground wire, and one neutral wire. All phase loads are connected at a common or neutral point and the neutral wire is connected at this point. 


Case 1: When the loads are balanced, no current passes through the neutral wire. 

Case 2: When the loads are unbalanced, current passes through the neutral wire.


WYE configuration provides two ways to connect the load in the circuit, namely line-to-line and line-to-neutral. It can be used either as a 4-wire circuit and a 5-wire circuit. In this filter, capacitors have lower voltages. For instance, the 208V AC system uses 120V AC. Low voltage capacitors lead to reduced weight and volume, thereby saving cost. 

How to Design a WYE 3-Phase EMI Filter 

Follow these steps to design a WYE 3-phase EMI FIlter

  1. Identify the maximum power needed by the load.

  2. Obtain power per phase. For this, divide the result of step 1 by three.

  3. Divide the result of step 2 by the line-to-neutral (or line-to-ground) voltage.


Advantages of WYE Configuration

  • Ideal for power distribution to large distances. Supports 1-ⲫ, 2-ⲫ, and 3-ⲫloads.

  • Good for unbalanced loads as the star point is grounded.

  • Require less insulation for supporting the same voltage.

  • Used in applications requiring less starting current.


On comparing both the power line filters, it was found out that the 3-phase Delta EMI filter is technically more cost-effective. Unlike the 3-phase WYE EMI filter, it requires only three conducting wires which eventually reduce the cost of building the filter. But, if high voltage components are used, the cost-benefit gets offset.


Comments

  1. AnkurApril 22, 2022 at 12:34 AM

    The information you've shared through this blog is very useful and relevant, really such useful information for EMI filters . Expecting more content which will give us advance detail for this sort of topic.

    ReplyDelete

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