What is a motor rotor bar?
Rotor design The rotor windings are made up of rotor bars passed through the rotor, from one end to the other, around the surface of the rotor. The bars protrude beyond the rotor and are connected together by a shorting ring at each end. The bars are usually made of aluminium or copper, but sometimes made of brass.
What are the reasons for the damage of rotor bars in induction motor?
Another common reason is over current e.g. due to jam condition of the rotor [3], but there can be various reasons that will lead to cracking or broken rotor bars [4]: 1) Thermal stress due to over-load, non-uniform heat distribution, hot spot and arc; 2) Magnetic stresses due to electromagnetic forces, magnetic …
What is rotor in induction motor?
The rotor is a moving component of an electromagnetic system in the electric motor, electric generator, or alternator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor’s axis.
What is the formula of current in rotor bar in induction motor?
With increased rotor resistance starting torque will increase. As a guide line the rotor bar current density can be assumed between 4 to 7 Amp/mm2 or may be selected from design data Hand Book. Hence sectional area of the rotor bars can be calculated as Ab = Ib /δb mm2.
Why do rotor bars break?
1) Natural Degradation All of that movement leads to friction within the components. That causes natural wear and tear in the different elements. With enough friction, the rotor bars eventually give way. Regular maintenance can help you stay on top of this degradation.
What is rotor frequency?
The frequency of the rotor current fr = Ns x P/120, so fr = 0 if the slip is zero. If the operating speed is zero, Ns = N and the frequency of the rotor current is the same as the frequency of the stator current . f = source frequency in Hz.
What causes rotor failure?
Various stresses can cause rotor failures: thermal, magnetic, dynamic, environmental, mechanical, and residual. When installed and operated as designed, the stresses remain within tolerance and the motor operates properly for years.
What are the two types of rotor?
Induction motor rotor is of two types:
- Squirrel Cage Rotor.
- Wound Type Rotor or Slip Ring Type Rotor.
What are the three components induction motor rotor?
The stator of the three-phase induction motor consists of three main parts :
- Stator frame,
- Stator core,
- Stator winding or field winding.
How is rotor current calculated?
4.6
- Ns is the synchronous speed.
- and Nr is the rotor speed.
- Rotor current frequency (fr) = (s)(f)
- Rotor current frequency (fr) = 0.05 x 50.
- fr = 2.5 Hz.
What is a broken rotor?
Most rotor damage takes the form of cracks, usually around the base of the disk where it joins the hub section. Radial cracking outward can also occur but is more rare. Other occasional rotor problems include warping, heat-checking, and rotor bluing, which happens when a rotor has been subjected to high heat.