3 phase Induction motor speed control by v/f method Prepared by:- Dobariya Nilesh Bhuva jaydeep Upadhyay pranav

Outline..... Introduction Component list Basic overview of speed control method v/f method for speed control Basic block diagram Simulation circuit and waveform Advantages

Introduction In industry traditionally AC machines have been used in constant speed applications, whereas DC machines were preferred for variable speed drives. DC machines have the disadvantages of higher cost and maintenance problems with commutators and brushes. Commutators and brushes do not permit a machine to operate in dirty and explosive environment. An AC machine overcomes the drawback of DC machines. Although currently, the majority of variable speed drive applications use DC machines, they are progressively being replaced by AC drives. While there are different methods of speed control of induction motor,Variable Voltage Variable Frequency (VVVF) or V/F is the most common method of speed control. This method is most suitable for applications without position control requirements or the need for high accuracy of speed control.

Components list Power diode:- Price-42 Rs. Rating-500v. Mosfets:- Price-150Rs. Rating :- Volt: 700V, Current: 5A.

PIC microcontroller (16F877A) 3 ph.induction motor:- Rating: Volt: 415 V, Current: 2A, Power: 1HP(735 W), Speed: 1400 rpm Components list

Basic types of speed control method Speed control by varying voltage Speed control by varying frequency Speed control by v/f method

Speed control by varying voltage

Speed control by varying frequency

Speed control by v/f method The increase in the supply frequency increases the motor speed and also reduces the motor speed. The increases in voltage results in an increases in the maximum torque of the motor. If we combine these two features, we can achieve a control design by which the speed increases and the torque is kept the same. This is known as voltage/frequency control.

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Basic block diagram

Simulation circuit

o/p of rectifier

o/p of inverter

Measurement of rotor current

Measurement of stator current

Measurement of rotor speed

Measurement of torque

Advantages The speed of three-phase induction motor is being controlled by varying supply voltage and frequency with constant (V/F) ratio. It is simple, economic to easier to design and implement in open loop.

Reference Power Electronics Handbook Muhammad h. rashid. Power Electronics Ned mohan. Fundamentals of Electric Drives - By Mohammad A El-Sharkawi.

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