Is there a relationship between torque magnitude and speed in a three-phase asynchronous motor?
The ideal result for a motor used to drag a load is a relatively high speed and large torque, regardless of the number of poles.
Determining and weighing the relationship between torque and speed is a key element in ac motor design and adaptability to actual working conditions.
Starting torque, rated torque, and maximum torque are the primary performance indicators for induction motor products.
Starting torque reflects the motor’s ability to start, maximum torque reflects its overload ability, and rated torque is the normal working ability of the electric motor product.
The relationship between torque size and electric motor speed can be visually described through specific characteristic curves, which reflect the ac motor’s speed.
The motor speed can be quantitatively described through the rate of difference.
A higher rate of difference indicates that the motor’s speed is more different from the synchronous speed.
High turndown motors are used to meet the special requirements of certain applications.
Compared to ordinary motors with the same number of poles and power, high turndown motors have smaller blocking currents and can operate from zero speed to rated speed.
The stable operating speed range of the motor is also wider.
From the characteristic curve of the three-phase asynchronous motor, it can be seen that the electric motor torque increases with speed from the moment the motor starts, and the motor torque reaches a peak when theinduction motor speed reaches a certain state close to the synchronous speed.
As the motor speed increases again, the 3 phase motor torque decreases.
When the industrial motor speed is synchronized with the rotating magnetic field, the motor torque is zero, which is the working principle and characteristic of the asynchronous motor.
Under the rated operating conditions of the three-phase asynchronous motor, the motor speed is very close to the speed of the corresponding stator rotating magnetic field.
The motor has a very low rate of rotation, and under normal operating conditions, most of the cage motors have a turndown rate of no more than 10% at full load.
When the corresponding rotor impedance is mainly resistive, it has nothing to do with the turndown rate.
Additionally, the rotor current is almost proportional to the turndown rate because the rotor winding is in a short circuit.
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