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In vector control, an AC induction or synchronous motor is controlled under all operating conditions like a separately excited DC motor. [21] That is, the AC motor behaves like a DC motor in which the field flux linkage and armature flux linkage created by the respective field and armature (or torque component) currents are orthogonally aligned such that, when torque is controlled, the field ...
Thus it is not possible to control the motor if the output frequency of the variable frequency drive is zero. However, by careful design of the control system it is possible to have the minimum frequency in the range 0.5 Hz to 1 Hz that is enough to make possible to start an induction motor with full torque from a standstill situation. A ...
Small variable-frequency drive Chassis of above VFD (cover removed). A variable-frequency drive (VFD, or adjustable-frequency drive, adjustable-speed drive, variable-speed drive, AC drive, micro drive, inverter drive, variable voltage variable frequency drive, or drive) is a type of AC motor drive (system incorporating a motor) that controls speed and torque by varying the frequency of the ...
A variable frequency drive (VFD) or variable speed drive (VSD) describes the electronic portion of the system that controls the speed of the motor. More generally, the term drive, describes equipment used to control the speed of machinery. Many industrial processes such as assembly lines must operate at different speeds for different products.
V/Hz control is also sometimes referred to as scalar control or variable voltage, variable frequency (VVVF) control. Higher performance load applications are increasingly been been used for AC drives with multi-level and cellular inverter topologies and closed loop and sensorless vector or DTC control. [3].
The scalar control has been to a large degree replaced in high-performance motors by vector control that enables better handling of the transient processes. [1] Low cost and simplicity keeps the scalar control in the majority of low-performance motors, despite inferiority of its dynamic performance; [ 3 ] vector control is expected to become ...
Variable frequency drives implement the scalar or vector control of an induction motor. With scalar control, only the magnitude and frequency of the supply voltage are controlled without phase control (absent feedback by rotor position). Scalar control is suitable for application where the load is constant.
A permanent magnet synchronous motor and reluctance motor requires a control system for operating (VFD or servo drive). There is a large number of control methods for synchronous machines, selected depending on the construction of the electric motor and the scope. Control methods can be divided into: [21] [22] Scalar control. V/f control ...