Table of Contents
- 1 Do induction motors have constant torque?
- 2 What is the condition for maximum torque developed at starting?
- 3 What is constant in induction motor?
- 4 Why is VF ratio kept constant?
- 5 How does an induction motor develop torque?
- 6 How does an induction motor operate in steady state?
- 7 What are the advantages and disadvantages of induction motors?
Do induction motors have constant torque?
Typically, the induction motor is designed to provide a continuous torque rating of about 40\%–50\% of its maximum torque. (b) Constant power: For higher speed, the frequency of the inverter can be increased, but the supply voltage has to be kept constant at the maximum value available in the supply.
What is maximum torque in induction motor?
So, when slip s = R2 / X2, the torque will be maximum and this slip is called maximum slip Sm and it is defined as the ratio of rotor resistance to that of rotor reactance. NOTE: At starting S = 1, so the maximum starting torque occur when rotor resistance is equal to rotor reactance.
What is the condition for maximum torque developed at starting?
It can be proved that starting torque will be maximum when rotor resistance/phase is equal to standstill rotor reactance/phase.
Why V F ratio has to be kept constant when an induction motor operates below on the line frequency?
Higher flux than its rated capacity leads to increased eddy current and hysteresis losses. The increased losses cause the heating of the core and as a result of this the insulation of core will get damaged. Therefore, when motor running through VFD the V/f ratio is kept constant.
What is constant in induction motor?
An AC induction motor is supposed to be a constant power motor, which implies it draws more current on low voltage. Consider a motor running a constant torque load at a particular speed. The starting should be greater the system torque at time of starting. …
How does induction motor create torque?
Induction Motors An induction motor develops torque by inducing current to the rotor, which is proportional to the differential speed of the rotor and the rotating magnetic field in the stator. For NEMA design B motors the differential speed (called slip) is between 1\% and 2\% at full load.
Why is VF ratio kept constant?
From above equation ratio V/f is directly proportional to maximum value of flux as N is constant for the motor. Magnetic material of core of stator gets saturated if flux is increasing beyond limit. This is the reason to keep V/f ratio constant so that magnetisation of core remain same.
What does constant torque mean?
Constant torque loads require the same amount of torque at low speeds as at high speeds. Torque remains constant throughout the speed range, and the horsepower increases and decreases in direct proportion to the speed. With constant torque loads, the torque is not a function of speed.
How does an induction motor develop torque?
An induction motor develops torque by inducing current to the rotor, which is proportional to the differential speed of the rotor and the rotating magnetic field in the stator. For NEMA design B motors the differential speed (called slip) is between 1\% and 2\% at full load.
How do you find the maximum torque of an induction motor?
From this equation, we can see that the maximum torque of the induction motor is proportionate to the square of the input voltage (V) and inverse proportionate to the impedance of the rotor and reactance of the rotor. If the motor has a smaller value of reactance, then it will have a large amount of maximum torque.
How does an induction motor operate in steady state?
In steady state operation, an induction motor will operate at the speed where the mechanical load torque equals the torque developed by the motor. At low speeds, the difference between the motor torque and the load torque accelerates the machine. Normal operation is to the right of the maximum torque .
How does the torque affect the speed of the motor?
At low speeds, the difference between the motor torque and the load torque accelerates the machine. Normal operation is to the right of the maximum torque ( s < s p o). In this region, an increase in the load torque will cause the motor to slow, increasing the motor torque until an equilibrium is reached.
What are the advantages and disadvantages of induction motors?
In induction motors, field weakening is easily achieved over a wide speed range; this is not possible in permanent-magnet sine-wave-wound motors. The vector control of induction motors requires a considerable amount of computing power, and while microprocessors are an advantage they are not a necessity.