LATEST ELECTRICAL TECHNOLOGY MMD ORAL Q & A PART-5
Q Explain with the aid of sketch, the working principle of IGBT(Insulated Gate Bipolar Transistor) in varying motor speed control
This type of converter used for induction motor drives, uses transistors as switching devices.Unlike thyristors,...
LATEST TECHNICAL DEVELOPMENTS – PRACTICAL ELECTRICITY AND ELECTRONICS, HIGH VOLTAGE ON SHIPS
WHAT IS
HIGH VOLTAGE:
The International Electro technical Commission describe high voltage as
above (>)1000 V for alternating current(AC), & at least 1500 V for
direct current(DC) & differentiate it from low voltage (50–1000 V AC or
120–1500 V...
MAIN SWITCH BOARD (MSB) SAFETIES
MSB to be installed on the raised platform.
The location where the MSB is installed should have good ventilation, illumination & affected by minimum vibration.
No water or the oil pipes should pass above the MSB.
There...
MAIN SWITCH BOARD
Survey of MSB
Proper cleaning to be
carried internally as well as externally normally carried out when board is
completely dead (all generator stopped and prime mover locked off). Inspect for
dirt and dust (electro clean and vacuum...
MARINE DIESEL ENGINES NOTATIONS
There has been too much puzzle
with regards to the notations used for the Marine Diesel Engines. One can
consult the engine manual & find out what such notations means.
However, this article will
provide explanation for...
HIGH VOLTAGE VACUUM CIRCUIT BREAKERS
Vacuum switchgear follows the principle that it is virtually impossible
for electrical current to flow in a vacuum. Therefore, the main contacts
disconnected inside the vacuum bottle. The typical contact material consists of
a tungsten matrix impregnated...
SHAFT EARTHING
When steel is immersed in sea water (e.g. a ships hull) small galvanic current are initiated at anodic areas of the metal surface, causing corrosion.
Such corrosion prevail at the stern of a ship, where...
MOTOR STARTING METHOD
Star Delta Starter
This
is means of reducing
starting current of induction motor by initially connecting to the stator winding to ‘STAR’.
Once
the motor comes up to
speed (68%) to be connected
in DELTA.
When
motor start in ‘STAR’
it has the effect
of:
Reducing...
MEO CLASS IV FUNCTION-5 (EECEOL) ORAL QUESTIONS PART-3
Q. What is the meaning of power factor?
Ans- Power factor is the cosine of the angle between voltage and current waveform.
Q. How can it be improved?
Ans- Power factor improvement capacitor banks are used if...
AUTOMATIC VOLTAGE REGULATOR
Sudden load current surges (eg. Due to motor starting) on a generator causes a
corresponding change in its output voltage. This is due to an internal voltage drop in
the generator winding and effect is called...