As far as I understood, the rotor currents circulate through the aluminium bars embedded inside steel laminations. But why do they use steel for laminations instead of an insulator if the the idea is to loop the current only through the bars?
\$\begingroup\$
\$\endgroup\$
1
-
1\$\begingroup\$ What makes you think the aluminium bars are electrically connected to the steel laminations? \$\endgroup\$– Li-aung YipCommented May 11, 2015 at 9:49
Add a comment
|
1 Answer
\$\begingroup\$
\$\endgroup\$
3
Steel/Iron/Ferrous material are used for the rotor laminations to facilitate created a magnetic circuit, a key requirement of an electrical machine. The magnetic circuit is not meant to carry any electrical current. This is why they are laminated to reduce the loop size for the induced eddy currents. The thinner the laminations the smaller the eddy currents, great the efficiency
The slots are filled with electrically conductive material to facilitate creating an electromagnet. Aluminium can be used (for weight) but usually copper is used (conductivity). Sometimes silver (when weight and conductivity are paramount).
These windings are electrically insulated from the ferrous stator.
-
\$\begingroup\$ are there windings in the rotor? i read rotor has bars. \$\endgroup\$ Commented May 11, 2015 at 10:53
-
\$\begingroup\$ Not really, unless you consider the bars to be windings. The stator induces a current into the rotor bars (fairly high current due to the turns ratio), which creates a magnetic field which is then constrained by the laminate pole pieces. It is the interaction of the "Induced" current/Magnetic flux and the stator current/magnetic flux that causes the rotor to rotate (and gives the name Induction Motor) \$\endgroup\$– R DrastCommented May 11, 2015 at 11:01
-
\$\begingroup\$ windings, bars, the intent is the same - providing a current carrying path through rotor slots. For a squirrel cage yes they are bar. I distinguish between windings and bars due to the existence of something called "damper bars" in generators that compliment the rotor windings. \$\endgroup\$– user16222Commented May 11, 2015 at 11:41