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The engineering profession is now exceptionally wide-ranging; it covers every kind of product from dams to chemical plant to silicon chips, all having this in common: they have to be understood, designed, and made. What's more, they have to be made economically, efficiently, and better than the last time (or better than the competition). The qualities of a good engineer include
☆ Braking of Induction Motor
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■ Plugging of induction motors
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is done by interchanging any two of the supply terminals.
When the terminals are reversed the operation of the machine changes from motoring to plugging.
● From technical point of view and for better understanding, it can be said that:
the slip changes from ‘s’ to (2-s),
which indicates that due to reversal of the terminals the torque also changes its direction and braking occurs.
☆ Regeneration braking for induction motor
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Here, θs is the phase angle between the stator voltage and stator current,
→ whenever this phase angle exceeds 90° (i.e θs>90°) regenerative braking can take place.
To explain this more clearly and easily we can say that :
▶▶whenever the speed of the rotor exceeds synchronous speed, regeneration braking occurs.
▶▶ That is because whenever the rotor rotates at a speed more than synchronous speed there is a reverse field occurs which opposes the normal rotation of the motor and therefore braking takes place.
★ Main disadvantage of this type of braking is that:
the speed of the motor has to exceed synchronous speed which may not be possible every time.
★To acquire regenerative braking at a lower speed than synchronous speed, variable frequency source can be used.
28/10/2017
☆ Braking of Induction Motors
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When it comes to controlling an electric machine by electric drivers braking is a very important term
→ because it helps to decrease the speed of the motor according to will and necessity.
Braking of induction motors can be classified mainly in three types
◀Regenerative braking▶
◀plugging or reverse voltage braking▶
◀Dynamic braking▶ which can be further classified as:
● AC dynamic braking
● Self-excited braking using capacitors
● DC dynamic braking
● Zero sequence braking
01/10/2017
Conditions for protecting branch or distributed circuits for power distribution in LV
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2. Checking the protection conditions of the branch line(s) with regard to the thermal stresses
For branch lines with smaller cross-sections (S2
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