2. Tutorial: Mechanic - electrician Topic: Basics of electrical engineering the 2nd. Year Three-phase current Prepared by: Škarka Miloš Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002 je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

3. An inductive (asynchronous) machine is a rotary electric machine where it‘s magnetic circuit is divided by the small gap into two parts: the stator and the rotor. Both parts have a winding. One winding (usually on the stator) is connected to the source of the alternating current and the other (usually on the rotor) is connected on short distance and current in it comes from the electromagnetic induction which is similar to the transformer. That's why we call it an inductive machine.

4. The three-phase inductive motor is simple, reliable in operation and it doesn‘t require any special service or maintenance. It is being manufactured in wide range of performance: from a few watts up to 20MW with a very wide rotation range from tens of rotations per minute up to 100 000 rot/min. According to the design of a motor we distinguish:  a) motors with the armature on the short  b) motors with the binder armature

5. The rotary field created by the stator has a higher speed than rotor revs. The basis of asynchronous motor function is a creation of the rotary magnetic field, which comes from the alternating current passing through the winding of the stator. This magnetic field induce the voltage in the rotor and a formed current cause the power for rotating the rotor. Rotary field revs are determined by the frequency of the powering voltage taken from the network and by the number of poles in the three-phase motor. Where f is the frequency of the current and p is the number of pole pairs in the stator Function principle

6. terminalventilator terminal casing stator winding metal bundle of the stator short circuit circle shaft metal bundle of the rotor bearing

7. The motor with the armature on the short has the rotor winding made of bars, which are at the end connected on the short by conductive circles. The magnetic circuit is composed of metals to minimize losses caused by turbulent currents.

8. The binder armature – Except of the bundle of rotor metals there are even collecting circlets on the shaft. In rebates of metals there is a three- phase rotor winding made of insulated conductors connected to the star, rarely to the triangle. The winding of the rotor is connected to three collecting circlets, which can be also connected to active resistors used for the engine start. Armature with circletsBrushes on the collector

9. Stator winding Consist of three coils rotated by 120° powered by the three-phase current. This creates rotary magnetic field.

10. There are two ways how to connect the asynchronous motor In case of the connection to the star the voltage on coils is 230V In case of the connection to the triangle the voltage on coils is 400V Terminal of the asynchronnous motor connected to the star and to the triangle.

11.  Main parts of the asynchronous motor  The difference between the armature on the short and the binder armature  Describe the picture  What is the voltage on coils?

12. Picture 1Picture 2

13.  Wikipedia.cz  http://www.myinfo.sk http://www.myinfo.sk  http://referaty-seminarky.cz http://referaty-seminarky.cz  http://fei1.vsb.cz