3. PHASE FAULT DETECTION/SINGLE PHASING
This refers to the situation where any of the 3 phases has a fault hence the load is forced to draw all its current from the remaining phases. In most instances it leads to blowing /burning up of the load due to overheating caused by excessive current drawn by the operational phases. Because of its destructive effects, the loads have to be protected from its destructive effects. This can be done by connecting three contacts to the lines. These are controlled by coils on the neutral as shown below:
In the set up, I used three bulbs as the load but they can be replaced by a three phase induction motor. With this set up installed somewhere in your circuit if one phase has a fault, the whole system is disabled hence avoiding damages.
4. STAR-DELTA MOTOR CONNECTION SYSTEM
Star motor connection draws a lot of current from the grid. On the other hand, it enables the motor pick up the highest torque and speed within a short time. Delta motor connection draws considerably less current from the grid but doesn’t help motor attain its highest torque and speed. Because of these contrasting properties of the two systems, we can make use of them at different phases of motor control. This connection system uses the star connection to start the motor then disconnect it after 5 seconds and connect the delta connection. This ensures prudent use of power and proper motor speed for higher productivity.
The connection schematics is as shown below:
5. AUTOMATIC CHANGEOVER SWITCH
Abrupt power losses usually lead to damages to electrical appliances in an industry, motors included. Again they lead to a halt in production process. Because of these effects, it is desirable that a backup power source such as a generator be installed. This automatic switch should however give an interlude to confirm whether to bring in a generator or cut it off when the mains power is back.
The system I am proposing here first checks for a fault in any of the lines. It then gives an interlude of 5 seconds to turn the mains on after a power loss( due to a fault in any of the lines, total mains power loses etc.) and also to turn the generator on in case of power losses. This is done automatically just by the use of contactors.
The schematics is as shown below(I used 3 bulbs but you can connect a three phase induction motor). Try it out!
Above are the motor control techniques I sampled for you. Try them out, ask questions via the contact section down there and share with your friends.