What is Kramer system?

What is Kramer system?

Kramer System is a cascade connection of slip ring or Wound rotor Induction motor. Once motor is started using rotor resistance starter, the rotor terminals are thrown to. three phase bridge rectifier.

What are the advantages of static Kramer drive?

What are the advantages of static Kramer system? i. The drive system is very efficient and the converter power rating is low, because it has to handle only the slip power.

What are the causes of harmonic currents in static Kramer drive?

19. Harmonics in a Static Kramer Drive The rectification of slip-power causes harmonic currents in the rotor which are reflected back into the stator.

What is static rotor resistance control?

Static Rotor Resistance Control: The ac output voltage of rotor is rectified by a diode bridge and fed to a parallel combination of a fixed resistance R and a semiconductor switch realized by a transistor Tr (Fig. 6.51). Effective value of resistance across terminals A and B, RAB, is varied by varying duty ratio of.

What is a static Kramer drive?

Definition: The static Kramer-drive is the method of controlling the speed of an induction motor by injecting the opposite-phase voltage in the rotor circuit. The injected voltage increases the resistance of the rotor, thus controlled the speed of the motor.

What are the two types of static Scherbius system?

Sub-synchronous Generating – For sub-synchronous speed, the torque is required to be positive, although the slip is positive. The power is fed into the rotor through the slip ring. Super-synchronous Generating – When the speed of the motor above the synchronous speed, then the slip and torque becomes negative.

Why rotor slots are skewed?

The rotor or stator slot of the induction motor skewed through some angle so that the bars lie under alternate harmonic poles of the same polarity or other words, bars must be skewed through two pitches. The main purpose of skewing is to reduce the magnetic logging between the starter and the rotor.

How is rotor resistance calculated?

Under normal working condition r2/s≫ r1, x1 and therefore the equation becomes, This equation shows that for a constant torque, the slip is directly proportional to the rotor resistance. If the resistance in the rotor circuit is increased, the slip is increased and the speed of the rotor is decreased.

What is the drawback of rotor Rheostatic speed control method?

The major disadvantage of the rotor resistance control method is that the efficiency is low because of the additional losses present in the resistors connected within the rotor circuit. The efficiency is greatly reduced at low speeds because of the higher value of the slip.

What are the advantages of V F control?

The advantage of using V/F for speed control of three phase induction motor is as follows [2]: ● The current required at the starting is reduced. The motor runs more in stable region. Instead of simply running at its base rated speed the motor can be run typically from 5% of the synchronous speed up to the base speed.

What is the main motive while choosing the number of rotor slots?

Explanation: The number of rotor slots are decided for quieter operation of the machine. The number of rotor slots differs from the number of stator slots by more than the number of poles.

Which motor is best suited for domestic refrigerator?

Detailed Solution. Single phase induction motor is used in household refrigerator.