Star (Y or Wye) & Delta (Δ) Connections for Rotating Machines

Star (Y or Wye) & Delta (Δ) Connections

There are two type of connections are used for three phase rotating machine or induction motor. These are star & delta connection. Usually star connection is 4 –wire system & delta connection is 3 – wire system. Below fig. shows the star & delta connections:

·        Star ( Y or Wye ) Connection : There are 4-wire connection but 4-wire is optional. These 4^th wire is used as neutral wire (common wire) & other 3-wire is phase system . Therefore star connections there are two type of connections are possible .These are 3-phase 4-wire system & 3-phase 3-wire system. In star connection one end of three wire or phases connected to common point or it called as star point or neutral point. Its shape is look like Y as shown in above fig. In rotating machine only 3-wire connections are used to give supply to machine.in this line voltage & phase voltage are different. Line voltage (Vl ) = √3 Phase Voltage (Vp) . With star connection we can used two different voltages. E.g. 230 Volt / 400 Volt .The voltage between ant of the three phases wire & neutral wire is 230 Volt. Whereas the voltage between the two phases is 400 Volt. In star connections line current & phase current are same. Star connections are often used in application which require less starting current. Since insulation require is less. Usually star connections are used for small machine or machine rated up to 2.2 kW. Total three phase power is calculate in star connection by using following formula :

P =  √3 *VL*IL* cos Φ

Where ,

P = Power in watts or kilowatts                                                       

VL = Line Voltage in Volt

IL = Line Current in Ampere

cosΦ  = Power Factor

·        Delta Connection (Δ): Delta connection, only 3-wire 3-phase system is possible. Every wire is connected to two adjacent wire in form of triangle (Δ) and all three common point connected from three phases. There is no neutral wire on neutral point in delta connection. Line voltage ad phase voltage are same in this connection. Whereas line current (IL) =   √3 phase current (IP). In this line voltage &phase voltage is same therefore more insulation is require in individual phases. Delta connections are often used in application which require high starting torque. Generally rotating machines or induction motor above 2.2 kW is Delta connected. Total three phase power is calculate in delta connection by using following formula :

P =  √3 *VL*IL*cosΦ

Where ,

P = Power in watts or kilowatts

VL = Line Voltage in Volt

IL = Line Current in Ampere

cos Φ  = Power Factor 

Following fig. shows the connections of Star & Delta configuration :