Speed control of induction motor in steady state

In summary, in this experiment, we learned about vector control of an induction motor using the constant rotor flux linkage method. The phase current is directly related to the speed instruction on the x-axis, and the line voltage remains constant. The torque-speed curve can be used to determine the optimal operating point for the motor.
  • #1
MissP.25_5
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In this experiment, we'd learn about vector control of an induction motor. By using the constant rotor flux linkage vector control method, An AC induction motor can achieve a DC motor-like performance.
Firstly, we tested on speed control response in steady state.
*the proportional gain kp = 2.0 (rated value) and the integral gain kI= 20.0 (rated value)

The x-axis represents speed instruction (or speed command)

My questions here are:
1. Can someone explain the rise and fall of the phase current?

2. Can we extend the line voltage to the y-axis? (it'd look something like a V-shape)
 

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Sure, I would be happy to explain the rise and fall of the phase current in this experiment. The rise and fall of the phase current is directly related to the speed instruction (or speed command) on the x-axis. As the speed instruction increases, the phase current also increases to match the required torque to achieve that speed. Similarly, when the speed instruction decreases, the phase current decreases as well.

To answer your second question, it is possible to extend the line voltage to the y-axis, but it would not look like a V-shape. The line voltage would actually be a constant value, as it is the input voltage to the motor and does not change with the speed instruction. The V-shape you are referring to may be the shape of the torque-speed curve, which shows the relationship between the motor's torque and speed at different levels of voltage and current. This curve can be used to determine the optimal operating point for the motor in terms of efficiency and performance. I hope this helps to clarify your questions.
 

1. How is speed controlled in an induction motor in steady state?

In an induction motor, the speed can be controlled by varying the frequency of the power supply. This is known as variable frequency drive (VFD) control. By increasing or decreasing the frequency, the speed of the motor can be adjusted accordingly.

2. What is the role of stator voltage in speed control of an induction motor?

The stator voltage plays a significant role in controlling the speed of an induction motor. By varying the voltage, we can control the torque produced by the motor, which in turn affects the speed. Lowering the voltage decreases the torque and thus decreases the speed.

3. Can the speed of an induction motor be controlled without changing the frequency?

Yes, the speed of an induction motor can also be controlled by changing the number of poles in the stator. This can be achieved by using a multi-speed motor or by using a variable speed drive with multiple poles.

4. How does the load affect the speed control of an induction motor in steady state?

The load on an induction motor affects its speed control in two ways. Firstly, if the load increases, the torque required for the motor to maintain its speed also increases. This results in a drop in speed, unless the voltage or frequency is adjusted. Secondly, the type of load (constant or variable) also affects the speed control strategy used.

5. What are the advantages of using a VFD for speed control of an induction motor?

Using a VFD for speed control has several advantages over other methods. It allows for precise and smooth speed control, energy savings, and better control over torque and power. It also eliminates the need for mechanical starters and reduces the wear and tear on the motor and other equipment.

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