MATERIAL

Explanations of terms

  • VL : Line voltage (V)
  • : Phase voltage (V)
  • IL : Line current (A)
  • : Phase current (A)
  • : Power (W)
  • : Resistance (ohms)
  • : Time (seconds)
  • : Heat quantity (cal)

Power

“Power” is the heat generated inside a conductor due to electrical resistance when current flows through the conductor. The formula expressing the quantity of heat is shown on the right.

Power

Joule heat

“Joule heat” is the quantity of work that the current performs in a specified unit of time.

Joule heat

Units of heat quantity

The unit shows the quantity of heat required to increase the temperature of 1 g of water by 1℃ and is known as a calorie. 1(kcal) = 4186 (J)(W, seconds)

Units of heat quantity

Ohm’s law

Ohm’s law states that the strength of a current flowing through a conductor between two points is directly proportional to the potential difference across the two points, and inversely proportional to the resistance between those two points.

Ohm’s law

Combined resistance of serial connections

As the current meeting points of serially-connected resistance is the same at each point, if you assume a voltage drop for each point of resistance of V1, V2 and V3 and take theflowing current as I (A), V1 = IR1, V2 = IR2 and V3 = IR3 so the combined resistance (R) is shown by R = R1 + R2 + R3.

Combined resistance of serial connections

Combined resistance of parallel connections

The combined resistance R (ohms) in the case where all of the points of resistance R1, R2 … Rn (ohms) are connected in parallel is expressed using the formula shown on the right.

Combined resistance of parallel connections

Three-phase AC circuit

A three-phase AC circuit is an electrical circuit where 3 alternating currents of equal size and frequency pass at phases shifted successively by 120º.

Three-phase AC circuit

Components of heating wires

  Ni Cr Al Mn C Others Fe
Nichrome type 1 77 or more 19~21 - 2.5 or less 0.15 or less 2.0 or less 1.0 or less
Nichrome type 2 63~67 15~18 - 1.5 or less 0.15 or less 2.0 or less Remnant
Ferrochrome type 1 - 23~26 4~6 1.0 or less 0.10 or less 3.0 or less Remnant
Ferrochrome type 2 - 17~21 2~4 1.0 or less 0.10 or less 3.0 or less Remnant

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