# Practical Work of Three-Phased Induction Motor Modeling in a Classical Spreadsheet Software
## 2 Three-Phased Induction Motor
### Realization of an Induction Motor  
The **stator** consists of a ferromagnetic cylinder with slots to accommodate the windings. This cylinder is made up of a stack of laminated ferromagnetic sheet metal plates in order to limit eddy currents. It is common practice to provide additional protection against abnormal windings that have been overheated by placing either a thermal circuit breaker or a temperature sensor at the heart of the windings. When protection devices trip, the power supply is cut off. The motor is connected to the electrical network via a terminal board, where all the connections are grouped together. There are therefore six connections for the stator windings: three windings \(\times\) two ends (plus possibly two others for the temperature sensor). Four types of **rotor** can be distinguished:Squirrel cage rotor or short-circuited rotor: This is the most common type of rotor and it was invented by [PERSON] in the early 1890s [15]. It consists of a stack of laminated ferromagnetic sheet metal plates, just like the stator, and conductive bars that are regularly distributed around the periphery of the rotor. The bars are interconnected by two short-circuit rings, as presented in Figure 1. The ferromagnetic sheets are used to guide the field lines while the bars accommodate the induced currents. For low-power machines, the rotors are made from a stack of sheets cut and insulated from each other (lamination), into which a conductive material is injected so as to form the bars, as well as the short-circuit rings. For high-power machines, the bars are inserted into the rotor and then the short-circuit rings are welded or brazed to the bars. The material constituting the bars and the short-circuit rings is generally an aluminum-based alloy, but copper or brass can also be found. In general, the bars are slightly inclined along the axis of the rotor so that the number of bars present under a stator phase is constant regardless of the angular position of the rotor. This method makes it possible to reduce the magnetic circuit reluctance variation during the rotor rotation (notch effect) and thus reduce the torque oscillations. This inclination of the bars and notches, along with the short-circuit rings, gives this rotor the shape of a deformed _squirrel cage._
2. Double-cage rotor: This rotor is built on the principle of the single-cage one, but with two electrically independent cages. An external cage at the periphery of the rotor is made of less conducting materials (brass, bronze) and has low inductive leakage. An internal copper cage has higher conductivity and high inductive leakage. The external cage, which is especially active at start-up, makes it possible to obtain a greater torque in this phase of operation, while, at nominal speed, the internal cage makes it possible to achieve the characteristics of a single-cage rotor. 3. Double-notched or deep bar rotor: These rotors are cage rotors that use the skin effect in the conductors to vary the resistance of the rotor depending on the operating speed of the machine. The skin effect is an electromagnetic phenomenon where the more the frequency of the currents increases, the more the current tends to circulate only on the surface of the conductors. Thus, at start-up, the frequency of the rotor currents is equal to that of the power supply, and the current only uses the upper part of the bar. Then, with the rotor speed increase, the rotor currents frequency decrease and the current uses the increasing surface area of the bars. These rotor topologies allow starting with a higher torque when the machine is powered by a fixed voltage source (without a drive, which is not the purpose of this work). 4. Ring rotor or wound rotor: The rotor of such a machine consists of three coils. Each coil is connected to a ring. The rings make it possible to have an electrical circuit connection with the coils of the rotor.