### Explanations of terms

**ＶL**: Line voltage (V)**Ｖ**: Phase voltage (V)**ＩL**: Line current (A)**Ｉ**: Phase current (A)**Ｗ**: Power (W)**Ｒ**: Resistance (ohms)**ｔ**: Time (seconds)**Ｑ**: 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.

#### Joule heat

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

#### 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)

#### 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.

#### 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 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.

#### 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.

#### 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 |