Watlow Heater Catalog

Reference Data (SI Unit)

Equations

Typical 3-Phase Wiring Diagrams and Equations for Resistive Heaters Definitions For Both Wye and Delta

3-Phase Delta (Balanced Load)

I L

(Balanced Loads) V p = Phase voltage V L = Line voltage I p = Phase current I L = Line current R = R 1 = R 2 = R 3 = = Resistance of each branch W = Wattage Wye and Delta Equivalents W DELTA = 3 W WYE W ODELTA = 2 / 3 W DELTA W OWYE = 1 / 2 W WYE

R 1

R 2

V P

I P

V L

R 3

I L

Equations For Delta Only I P = I L /1.73 V P = V L W DELTA = 3 (V L 2 )/R W DELTA = 1.73 V L I L

3-Phase Open Delta

3-Phase Wye (Balanced Load)

I L01

I P

R 2

I P01

V P

R 1

V P

V L

R 1

I P03

V L

R 3

R 3

I L

I L02

I L03

Equations For Wye Only I P = I L V P = V L /1.73 W WYE = V L 2 /R = 3(V P 2 )/R W WYE = 1.73 V L I L

Equations For Open Delta Only V P = V L I PO1 = I PO3 = I LO2

I LO3 = 1.73 I PO1 W 0DELTA = 2 (V L

2 /R)

3-Phase Open Wye (No Neutral)

I PO

R 2

V PO

V L

R 1

I LO

Equations For Open Wye Only

I PO = I LO V PO = V L /2 W 0WYE =

1 / 2 (V

2 /R) 2 /R)

L

W 0WYE = 2 (V PO W 0WYE = V L I LO

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