Preparation Ass. 2 Reduced Voltage Starters Autotransformer Star - - PowerPoint PPT Presentation

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Dec 08, 2022 346 likes •481 views

Preparation Ass. 2 Reduced Voltage Starters Autotransformer Star Delta VFD Solid State Resistive Starting Autotransformer Starter Coil in each phase Motor starts with an inductive load As the motor gains speed

SLIDE 1

Preparation Ass. 2

SLIDE 2

Reduced Voltage Starters

Autotransformer
Star – Delta
VFD
Solid State
Resistive Starting

SLIDE 3

Autotransformer Starter

Coil in each phase
Motor starts with an inductive load
As the motor gains speed the coils

are removed from the circuit

SLIDE 4

Star Delta Starter

LC3-D Star/ Delta Motor Starters
Star Delta motor starter for squirrel

cage motors

Fitted on open frame structure
Maximum frequency: 30 starts/

hour

Starting delay: 30 seconds
Mechanical interlock included
Auxiliary contact: 1N/C

SLIDE 5

SLIDE 6

Star Delta Starter

Star formation draws less initial current
Star will have less torque
Delta – more current and more torque
Motor starts in Star and then as near synchronous speed is achieved

switches to Delta

Switch over can be done through a timer, rev counter or centrifugal

switch.

SLIDE 7

Resistive Starting

Resistors are added to the

windings

As motor starts and gains speed

the resistances are removed

SLIDE 8

VFD – Variable Frequency Device

SLIDE 9

VFD

The frequency of the three phase current is varied
The starting frequency is low and gradually increased to the desired

speed

Current into the motor is controlled by varying the frequency of the

three phase current

SLIDE 10

Control Gear for three phase motors

Direct Online Starter
Emergency Stop
Fuses
Starters
Overload Protection
Single Phase Protection
Speed Changing Mechanisms (VFD, Gear Box)
Braking systems
Changing of direction of rotation

http://www.ckit.co.za/secure/conveyor/troughed/electric_motors/alstom/alstom---motorcontrol.htm

SLIDE 11

Effect of Excitation

Excitation is varied and refers to

the DC supply to the rotor

As the result the power to the

armature can be leading, lagging

r unity power factor
http://www.electrical4u.com/synchronous-motor-excitation/
http://www.ece.umn.edu/users/riaz/animations/syncmotie.html
https://en.wikipedia.org/wiki/Synchronous_motor

SLIDE 12

3 Phase Motor Explanation

https://www.youtube.com/watch?v=Vk2jDXxZIhs