# Question: What Is V F Method?

## What is the difference between VF control and vector control?

Magnetising current is the minimum current ( No load current) and increase in it does not help in better control of motor.

In v/f control we have no control over this current vector but in vector control we apply the pulses in such a way that magenetic component is statiory and torque genrating component is increased..

## What are the methods of speed control of induction motor?

Speed Control Methods of Induction Motor:Control From Stator Side:Control From Rotor Side:Speed Control by frequency variation:Speed Control By Pole Changing:Speed control by varying Supply voltage:Speed control by varying Rotor Resistance:Speed control by injected EMF:Speed control by Cascade Connection:Jan 9, 2017

## What is Torque in VFD?

HP and torque are both 100 percent at 60 hertz (base motor speed). When the VFD reduces frequency and motor speed, it also reduces voltage to keep the volts/hertz ratio constant. Torque remains at 100 percent, but HP is reduced in direct proportion to the change in speed.

## What is synchronous speed?

: a definite speed for an alternating-current machine that is dependent on the frequency of the supply circuit because the rotating member passes one pair of poles for each alternation of the alternating current.

## Why is VF ratio kept constant?

When the frequency is lowered (for slower motor speed), the magnetic field increases, and excessive heat is generated. When the frequency is increased (for higher motor speed), the magnetic field decreases, and lower torque is produced. In order to keep the magnetic flux constant, the V/Hz ratio must remain constant.

## What is V F control method?

V/F is abbreviated from voltage/frequency. V/F control is an induction motor control method which ensures the output voltage proportional with the frequency, so it maintains a constant motor flux, preventing weak magnetic and magnetic saturation phenomenon from happening.

## Which type of speed control method is more advantages?

Advantages of flux control method: (i) This is an easy and convenient method. (ii) It is an inexpensive method since very little power is wasted in the shunt field rheostat due to a relatively small value of Ish. (iii) The speed control exercised by this method is independent of the load on the machine.

## How do you calculate VF ratio?

V/f = 4.44 × N x Phi Phi is maximum value of flux, f is frequency and N is number of turns.

## What is the relation between frequency and voltage?

As the voltage increases so does the power out of the area and frequency then increases. This oscillation of power, voltage and frequency can last for several seconds.

## How do I create a VFD?

6 Step Basic Setup Of An SMV Variable Frequency DriveTurn Off All Line Power. SMVector Variable Frequency Drives come in four different voltages: 120 VAC, 240 VAC, 480 VAC and 600 VAC. … Wire The Input Line Voltage. … Wire The AC Motor. … Jumper The Drive Enable. … Power Up The Drive. … Finish Your Setup.Apr 16, 2015

## What are the advantages of V F control?

The advantage of using V/F for speed control of three phase induction motor is as follows [2]: ● The current required at the starting is reduced. The motor runs more in stable region. Instead of simply running at its base rated speed the motor can be run typically from 5% of the synchronous speed up to the base speed.

## What is VFD vector control?

Vector control, also called field-oriented control (FOC), is a variable-frequency drive (VFD) control method in which the stator currents of a three-phase AC or brushless DC electric motor are identified as two orthogonal components that can be visualized with a vector.

## What is the slip?

Slip is the differentiation between synchronous and asynchronous speed. … The difference between the synchronous speed of the electric motor magnetic field, and the shaft rotating speed is slip – measured in RPM or frequency. Slip increases with increasing load – providing a greater torque.

## Where are VFD used?

The most common uses of a VFD are for control of fans, pumps and compressors, and these applications account for 75% of all drives operating globally. Soft starters and across-the-line contactors are other, less sophisticated types of motor controllers.

## Which motor is suitable for lift?

AC slip ring or DC compound motors are prefer for lifts. Shunt type commutator motors are preferred in case of single phase installation. The latest lift designs use 3-phase induction motors with variable frequency drive electronic controls.