4.2 Induction Machines Control
Squirrel cage types of Induction Motors (IM) have been considered for a long time as the workhorse in industry . It has been claimed that 90% of installed motors are of this type. Among the reasons for their popularity are robustness, reliability, low price, and relatively high efficiency.
Different control methods are popular in the industry (e.g. scalar method (named V/f), vector control, direct torque control, etc.). In this chapter, we will first describe the V/f method, and then focus on the vector control approach.
4.2.1 Control of Induction Motor using V/f Method
The aim of this section is to model a scalar control method for IM, named V/f = constant. This method is the simplest way for controlling this type of machine.
In this type of control, a constant ratio between the voltage magnitude and frequency is maintained. This is to keep it constant and is the optimal flux in the machine.
A well-known machine model is presented in Chapter 2 and can be rewritten as [1–8]:
It is assumed that the co-ordinate system is connected with stator current, hence:
which in a steady state would be