Electrical Engineering Interview Questions, Tipsengineerzone.in

Electrical Engineering Interview Questions

A circuit breaker is an
automatically operated electrical switch designed to protect an electrical
circuit from damage caused by excess current from an overload or short circuit.
Its basic function is to interrupt current flow after a fault is detected.

Differential protection is a unit-type protection for a specified zone or piece of equipment. It
is based on the fact that it is only in the case of faults
internal to the zone that the differential current
(difference between input and output currents) will be high.

Why is differential protection used?

Differential protection schemes are
mainly used for protection against
phase-to-phase fault and phase to earth faults. The differential
protection used for power transformers is based on Merz-Prize
circulating current principle. Such types of protection are
generally used for transformers of rating exceeding 2 MVA.

CORE LOSS

Core loss is
the loss that occurs in a magnetic core due
to alternating magnetization, which is the sum of the hysteresis loss and
the eddy current loss.

What is eddy current loss?

Eddy current loss is conductive
I2R loss produced by circulating currents induced
in response to AC flux linkage, flowing against the internal resistance of the
core.

No-load losses

It is the loss in a transformer that is excited at rated
voltage and frequency, but without a load connected to the secondary. No-load
losses include core loss, dielectric loss, and copper loss in the winding due
to exciting current.

PUMP

A pump is a device that moves
fluids (liquids or gases), or sometimes slurries, by mechanical action,
typically converted from electrical energy into hydraulic energy. Pumps can
be classified into three major groups according to the method they use to move
the fluid: direct lift, displacement, and gravity pumps.

Load Torque (T)

Load torque is very simple. As you
see this equation torque is the product of the force and the
distance between the force and the center of rotation. For example, if you want
to hold the force acting on the end of pulley, T = F x r.

Switchgear

In an
electric power system, switchgear is composed of electrical disconnect
switches, fuses or circuit breakers used to control, protect and isolate
electrical equipment. Switchgear is used both to de-energize equipment to allow
work to be done and to clear faults downstream

Why is it called switchgear?

The combination
of circuit or fuses, electrical disconnects switches or breakers used to
isolate, protect and control electrical equipment or gears from the defective
condition are usually called switchgear.

Switchgear

Definition: The apparatus used
for controlling, regulating and switching on or off
the electrical circuit in the electrical power
system is
known as switchgear. The switches, fuses, circuit
breaker,
isolator, relays, current and potential
transformer, indicating
instrument, lightning arresters and control panels
are examples of the switchgear devices.

Types
of Switchgear

The
switchgear is mainly classified into two types, the outdoors
type and the indoor type. For voltage above 66kV, the
outdoor switchgear is used. Because for the high voltage, the building work will
unnecessarily increase the installation cost owing to large spacing between the
conductor and large size of insulators.

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