Front Page | Johanson DMS, Inc. | Product Descriptions | Stock Heaters
Useful Formulas | Ordering Information | Therm. Cond. of Materials

Johnson DMS, Inc.

Formulas

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Design Hints - If the Volts and Watts are known, find the resistance in ohms, and browse the stock heater table that was sorted by ohms values. Then select some possible sizes to fit the application.

Cutting Watts by Half - The use of a properly rated diode in line would halve the power (watts) when used with AC voltage.

Doubling Voltage - The power is increased four times the original value then the voltage is doubled.

SOME USEFUL FORMULAS

VALUE ASSIGNMENTS
P = Power in Watts
E = Voltage, AC or DC
I = Current in Amperes
R = Resistance in Ohms
Resistors in Series = RS
Resistors in Parallel = RP

POWER FORMULAS

P=I2 R

P=E * I

P=E2 / R

CURRENT FORMULAS

I = E / R

I = square rootP / R

DELTA CONNECTION

I LINE = I LEG * square root3

E LINE = E LEG

P LEG = P TOTAL / 3

P LEG / (E LINE OR E LEG) = I LEG

E LEG / I LEG = R LEG

RESISTANCE FORMULAS

R = E / I

R = P / I2

R = E2 / P

RESISTORS IN SERIES

RS = R1 + R2 + R3

VOLTAGE FORMULAS

E = I * R

E = square rootP * R

RESISTORS IN PARALLEL

RP = (R1 * R2) / (R1 + R2)

WYE OR "Y" CONNECTION

I LINE = I LEG

E LEG = E TOTAL / square root3

I LEG = P LEG / E LEG

R LEG = E LEG / I LEG

More useful electrical formulas
Watts = Current X Voltage Degree C = (F-32 X 5/9
Watts = (Voltage X Voltage) divided by Resistance (Ohms) Degrees F = (C X 9/5) + 32
Watts = (Current X Current) X Resistance  
  Warm-up Watts (Watt Hours) req'd = C x M x (T2-T1) x .293
Voltage = Current X Resistance (Ohms) where C = specific heat of mat'l, M = mass in lbs.
Current = Voltage divided by Resistance (Ohms) T2 = ending temperature, T1 = starting temperature
Resistance (Ohms) = Voltage divided by Current  

Front Page | Johanson DMS, Inc. | Product Descriptions | Stock Heaters
Useful Formulas | Ordering Information | Therm. Cond. of Materials