Power formula OHM’S law P = Power in watts U = Voltage U = Voltage P = UI R = Resistance in ohms U = RI I= Current in amperes I= Current in amperes I= P/U U= P/I I= U/R R= U/I P= U2 /R R= U2 /P

### Heating elements connections

(Heating elements resistance “r” of unit power “p” with nominal voltage “U”)

 Parallel wiring Serial wiring Quantity of elements (n) Total resistance (R) Total power (P) 2 R = r/2 p = 2p 3 R = r/3 p = 3p X R = r/x p =xp NOTE: Watt density (W/cm2) for each element is unchanged
 Quantity of elements (n) Total resistance (R) Total power (P) Heating element Watt density (w/cm2) 2 R = 2r p = p/2 Devided by 4 3 R = 3r p = p/3 Devided by 9 X R=Xr p = p/x Devided by x2

### Delta and star element connections

Delta connection Star connection Delta (triangle) connection: The voltage supplied to the heating elements is the same than the power supply voltage measured between phases : U= Un Supply voltage (U) 230V, 3 phases 230V, 3 phases 400V, 3 phases 400V, 3 phases Heating elements nominal voltage (Un) 230V 400V 230V 400V Watt density (W/cm2) No change  in watt density Watt density is divided by 3 Watt density is multiplied by 6 No change in watt density Total power (P) Total power is 3 time nominal power of one heating element (P=3 p) Total power is divided by 9.lt is 1/3 of nominal power of one heating element (P= p/3) Total power is 9 time nominal power of one heating element (P=9 p) Total power is 3 time nominal power of one heating element (P= 3p) comments No problem solution This can be used a reduced power step by using a Star/ Delta (triangle) connection system Never use Fire hazard! This is the most common configuration
 Star connection : The voltage supplied to the heating elements is the same than the power voltage divided byv3: U=1.737Un). Example: power supply is 400V, the heating element is energized with 400/1.737= 230V Supply voltage (U) 230V, 3 phases 230V, 3 phases 400V, 3 phases 400V, 3 phases Heating element! nominal voltage (Un) 230V 400V 230V 400V Watt density (W/cm2) Watt density is divided by 3 Watt density is divided by 9 No change in watt density Watt density is divided by 3 Total power (P) Total power is 1/3 of total possible power : it is the same than one heating element (P=p) Total power is 1/9 of total possible power. 1/3 nominal power of one heating element (P= 1/3 p) Total power is 3 time nominal power of one heating element (P=3p) Total power is 1/3 of total possible power. it is the same than one heating element (P=p) comments Not recommended Not recommended This is the most standard connection, allows the same heaters to be used with 400V star connection or 230V delta connection without power change Not recommended