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What will happen to speed-torque characteristics of an induction motor is the rotor resistance is increased?
If Rotor resistance is increased torque is increased
What is double cage rotor and deep bar cage rotor?
deep bars in the rotor that result in higher rotor resistance at low speeds thus resulting in larger starting torques. The higher resistance is due to the skin effect.
Why rotor contactor in external resistance of slipring motor connected in delta?
rotor contactor are used to cut the resistance in slip-ring motor connected through resistance box. resistance is proportional to torque. so by controlling rotor contactor resistance can be controlled and hence torque can be controlled. for more information check torque and speed characteristic of wound motor.
Why use surge protecting resistor to generator rotor winding?
To limit the fault current used surge protective resistance in generator rotor winding to protect the rotor winding heavy damage.
Why armature winding resistance is less than field winding resistance?
An 'armature winding' is the rotor winding, and the 'field winding' is the stator winding.
What is the total copper loss when rotor is standstill?
It is the supply voltage divided by the rotor resistance including the resistance of the brushes.
What will happen to speed-torque characteristics of an induction motor is the rotor resistance is increased?
If Rotor resistance is increased torque is increased
What is double cage rotor and deep bar cage rotor?
deep bars in the rotor that result in higher rotor resistance at low speeds thus resulting in larger starting torques. The higher resistance is due to the skin effect.
Why rotor contactor in external resistance of slipring motor connected in delta?
rotor contactor are used to cut the resistance in slip-ring motor connected through resistance box. resistance is proportional to torque. so by controlling rotor contactor resistance can be controlled and hence torque can be controlled. for more information check torque and speed characteristic of wound motor.
Why will the rotor of a wound-rotor motor not turn if the rotor circuit is left open with no resistance connected to it?
Because there is no current flowing in the rotor, and thus there is no magnetic field in the rotor, and thus there is no torque between the rotor and the field.
Why use surge protecting resistor to generator rotor winding?
To limit the fault current used surge protective resistance in generator rotor winding to protect the rotor winding heavy damage.
What are the reasons for connecting resistance in the rotor circuit when starting wound rotor induction motors?
To limit the starting current in slip ring induction motors.
Why armature winding resistance is less than field winding resistance?
An 'armature winding' is the rotor winding, and the 'field winding' is the stator winding.
How do you calcuate resistance for slipring motor?
it is related to Slip ring rotor max.currents and voltage ...
Why the rotor winding of a synchronous motor is usually connected to an external resistance during start up?
because at start the motor draws larger quantity of current and this may affected the rotor windings in order to limit current always resistance is connected.
What type of motor is variable torque produced by varying the resistance of the secondary circuit?
Wound-Rotor
How liquid rotor resistance operate?
Re: Liquid Rotor Starter A variant of the induction motor, is the slip ring, or wound rotor motor. The induction motor has a "squirrel cage" rotor which is in effect a short circuited winding in the rotor. The start and run characteristics are influenced by the resistance and inductance of the rotor circuit. One of the problems of the induction motor, is that the start current is very high (600 - 900%) and the start torque is relatively low (120 - 200%) compared to the start current drawn. The induction motor has a speed at which maximum torque is produced and this is very close to full speed. By altering the resistance in the rotor design, we can alter the speed at which maximum torque is produced. Below this speed, the current goes high and the torque goes down. Above this speed, the current drops with the torque. The wound rotor motor, has a winding on the rotor that is not short circuited, but is brought out to slip rings. This enables the effective rotor resistance to be altered. By varying the rotor resistance while the motor starts, we can cause the speed of maximum torque to shift from zero speed up to very close to full speed in a number of steps. The big advantage of this, is that the motor is able to provide a high start torque (around 200%) and a low start current (around 200%) from zero speed to full speed. This is very god for starting high inertia and difficult start loads on relatively weak supplies. The rotor resistors can be cast resistors, wound resistors, or liquid resistors. With standard resistors, the stages are switched in and out by contactors to alter the resistance. With liquid resistors, the resistance can be varied by varying the immersion of probes in the electrolyte. This can be achieved by raising and lowering the probes, or the liquid level.
