by using a frequency tuner in input we can change input frequency and in this way speed of dc motor will also vary.
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Varying the frequency (VFD) only works on AC motors.
the speed of ac motor can be controlled by controlling the synchronous speed (Ns=120f/p). and synchronous speed can be varried or controlled by changing frequency or by changing poles. but practicaly pole can not be changed. but we can change the frequency. the frequency can be VFD (Variable frequency Drives). so the speed of ac motor can be chaged or controlled by VFD.
A variable frequency drive (VFD) refers to AC drives only and a variable speed drive (VSD) refers to either AC Drives or DC Drives. VFD's vary the speed of an AC motor by varying the frequency to the motor. VSD's referring to DC motors vary the speed by varying the voltage to the motor.
Answer #1 It varies the frequency fed to a synchronous AC motor. As the frequency changes, so does the motor speed. Answer #2 The formula for calculating speed is: (120 X motor supply frequency) / number of poles 120 is a fixed number, so is the number of poles for a given motor, hence the only variable is the motor supply frequency. AC drives vary the motor supply frequency in turn achieving speed control.
Variable frequency Drive is not compatible with a DC Motor. VFD can be used only with AC motors, where frequency plays a key role in defining the speed of the motor.
Use a variable Frequency Drive. Sold by ABB, Allen-Bradley, and many others.
In industrial, there is a device called variable frequency drive (allso frequency inverter, ac drive) to control the motor speed by adjusting output frequency.
A variable-frequency drive (VFD) is a system for controlling the speed of a rotational or linear alternating current (AC) electric motor by controlling the frequency of the electrical power supplied to the motor.[1][2][3] A variable frequency drive is a specific type of adjustable-speed drive. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, microdrives or inverter drives.
Variable frequency drives (VFDs) control the speed and torque of an electric motor by adjusting the frequency and voltage of the power supplied to the motor. They convert incoming AC power to DC, then back to AC at a variable frequency and voltage. This allows for precise control over the motor's speed and power consumption, leading to energy efficiency and optimized motor performance.
definitly it give more efficient than variable stator voltage.............but in variable frequency ...............the frequency is not only variable....it is E/F control.because to maintain constant flux......... USUALLY THIS SPEED CONTROL IS ODOPTING IN INDUSTRIES......
Assume a 3 phase AC Induction motor. The speed of the motor is derived by the formula N = (120/f)/P. N speed, f - frequency, P number of poles. In an induction motor P is fixed by the winding. f system frequency. Variable speed drives change the system frequency so that the speed (N) can be varied. Drive is a power electronic device through which the system frequency can be varied
Variable Frequency Drive
Variable frequency Drive is power electronic device in which electrical power is provided to a motor with desired voltage level and with a facility to change the base frequency to higher or lower frequency. Base frequency is 50 or 60 Hz depending upon the region in the world. The formula for speed in a 3 phase system is N = (120 x Frequency) / Number of poles. N being the speed. By changing the frequency the motor speed can be varied.