Switchgear and rectifiers are used to control, protect, and isolate electrical equipment. Switchgear includes disconnect switches, fuses, and circuit breakers, and is used to de-energize equipment for work and clear faults. Rectifiers convert alternating current to direct current through processes like half-wave and full-wave rectification. Common types of switchgear and rectifiers include low voltage switchgear, air circuit breakers, single-phase and three-phase rectifiers, which provide functions like electrical protection, isolation from live parts, and switching. Proper maintenance through inspection, testing, and cleaning helps ensure safe and reliable operation.

1. SWITCHGEAR & RECTIFIER
Vikas kumar
0133ec131184

2. SWITCHGEAR
switchgear is the combination 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.

3. Switchgear

4. Types:
LV Switchgear
MV Switchgear
Generally electrical
switchgear rated upto 1 KV is
termed as low voltage switchgear
The most common use of LV
switchgear is in LV distribution
board.

7. THE ROLE OF SWITCHGEAR IS :
ELECTRICAL PROTECTION
SAFE ISOLATION FROM LIVE PARTS
LOCAL OR REMOTE SWITCHING
The basic functions of
Switchgear

8. Periodic Maintenance
Preventive Maintenance
a) 2 yearly Maintenance
b) 4 yearly Maintenance
Importance Of PM
Through such PM, troubles can be detected in the
Early stages and corrective actions can be taken
before extensive damage occurs.

9. The most common use of LV switchgear is in
LV distribution board.
This system has the following parts
Incomer
The incomer feeds incoming electrical
power to the incomer bus.
The switchgear used in the incomer should
have a main switching device.
The switchgear devices attached with incomer
should be capable of withstanding
abnormal current for a short specific duration
in order to allow downstream devices to
operate.
Generally Air Circuit Breakers are preferably
used as interrupting device.
Sub – Incomer
These sub – incomers draw power from main
incomer bus and feed this power to feeder bus
Feeders
Different feeders are connected to the feeder
bus to feeds different loads like, motor loads,
lighting loads, industrial machinery loads, air
conditioner loads, transformer cooling
system loads etc.

10. Main Transformer Incomer

11. Busbar
Busbar is a strip or bar of copper, brass or aluminium that conducts
electricity within a switchboard, distribution board, substation,
The cross-sectional size of the busbar determines the maximum amount
of current
Used to interconnect the loads and sources of electrical power.

12. Busbar Specification
Manufacturer: Nova Magrini Gallilio
Type of Busbar : Copper ( Insulated with Silver coated joints)
Busbar Rating : 1500 Amp
Method Of Cleaning : Clean with Lint Free Cloth
Busbar Dimensions : 2*100*8 mm
Busbar Maintenance
Full Bus Bar Inspection check for overheating signs, visual
inspection of Cu plate and nut bolts. cleaning of incoming/outgoing
spouts.
Remove dust with vacuum cleaner.
Cleaning and lubricating mechanical links with contact grease.
Check operating mechanism of shutter.
Contact Resistance of Electrical joints.
Check IR to earth and between phases on busbar and outgoing
circuits @ 2500V

13. Air Circuit Breaker (ACB)
A circuit breaker is an automatically operated electrical switch designed to protect
an electrical circuit from damage caused by overload or short circuit. Its basic
function is to detect a fault condition and interrupt current flow

14. Air Circuit Breakers : Charging method
Circuit breaker closing springs may be compressed manually or by means
of a small electric motor.
The closing coil is charged by manual charging handle. For closing, first
charge the spring by using the charging handle

15. Maintenance of Air Circuit Breaker
LV Circuit Breakers operating at 600 volt and
below, should be inspected
Maintained every 1 to 4 years depending on their
services and operating
Conditions.
Conditions that make frequency maintenance and
inspection are necessary:
High humidity and High temp
Dusty or Dirty Atmosphere
Corrosive Atmosphere

16. Inspection & Cleaning
Insulating parts including bushing should be cleaned
of dust
Clean & inspect Arc Chutes for Cracks, Broken Parts
. Replace Damage Parts
Inspect Breaker Operating Mechanism for loose
hardware & missing or broken etc
Examine for wears
Check Rack in/ out mechanism for normel operation
Lubricate if necessary
Check tightness of all terminations
Contacts maintenance
Arcing contacts to be verified for burn off
To be adjusted or exchanged that arc contacts
simultaneoslu when closing
Permissible tolerance 1mm
Adjust lead of arcing contacts from main contacts such
that when arc contacts
Meet then distance between

17. Insulation Resistance Test (Megger)
Load and line conductors should disconnected from the breaker to make
Test. IR between phases and phases w.r.t ground with breaker closed.
the result is compared against manufacturer/ pervious data
For breaker being tested.
Cycling the breaker
On & Off the breaker several times to check the correct operation
Of breaker.
Verify For Loop Check
Insert circuit breaker at test position and on & off the breaker
from remote location

18. Current Transformer
A current transformer (CT) is used for
measurement of alternating electric
currents

19. Relay
Relays is automatic device which senses an abnormal condition of
electrical circuit and closes its contacts. these contacts in turns close
and complete the circuit breaker trip coil circuit hence make the circuit
breaker tripped

20. General Precautions to be taken
Check the Electrical Isolation First
During maintenance Earth MUST be connected
Before maintenance of breaker spring must be discharge.
Don’t use compressed air on breaker
Don’t use file or emery paper for contacts cleaning
Inspection Inside Switchgear Room
Switchgear environment (switch room access and surrounds,
including fence and external walls if outdoors.
Signs of water
Signs of unauthorized access
Condition of firefighting equipment and warning notices
General Housekeeping

22. INTRODUCTION
• Rectifiers take a number of forms, including
vacuum tube diodes, mercury-arc valves,
copper and selenium oxide
rectifiers, semiconductor diodes, silicon-
controlled rectifiers and other silicon-based
semiconductor switches
• is an electrical device
that converts alternating current (AC) to direct
current (DC).
• The process is called rectification

23. RECTIFIER CIRCUITS
• Single-phase rectifiers
–Half-wave rectification
–Full-wave rectification
• Three-phase rectifiers
–Three-phase, half-wave circuit
–Three-phase, full-wave circuit

24. Single-phase rectifiers:
HALF-WAVE RECTIFICATION
• only one half of the input waveform reaches
the output which means voltage is lower
• the harmonic content of the rectifier's output
waveform is very large and consequently
difficult to filter.

25. Single-phase rectifiers:
HALF-WAVE RECTIFICATION
• Single diode rectifier
is connected across
an alternating
voltage source vS
▪ Since the diode only conducts when the anode
is positive with respect to the cathode, current
will flow only during the positive half cycle of
the input voltage.

26. Single-phase rectifiers:
HALF-WAVE RECTIFICATION
The waveforms for source voltage vS and output
voltage vo
• The output voltage varies between the peak
voltage vm and zero in each cycle. This variation
is called “ripple”, and the corresponding voltage
is called the peak-to-peak ripple voltage, vp-p.

27. Single-phase rectifiers:
HALF-WAVE RECTIFICATION
• If a DC voltmeter is connected to measure the
output voltage of the half-wave rectifier (i.e.,
across the load resistance), the reading
obtained would be the average load voltage
Vave, also called the DC output voltage.
• The meter averages out the pulses and
displays this average.
Output voltage and average voltage for half-wave rectifier

28. Single-phase rectifiers:
FULL-WAVE RECTIFICATION
• Full-wave rectification converts both
polarities of the input waveform to
pulsating DC (direct current), and yields a
higher average output voltage.

29. Single-phase rectifiers:
FULL-WAVE RECTIFICATION
• Full-wave center-tap rectifier: Top half of
secondary winding conducts during positive
half-cycle of input, delivering positive half-
cycle to load.

30. Single-phase rectifiers:
FULL-WAVE RECTIFICATION
• Full-wave center-tap rectifier: During negative
input half-cycle, bottom half of secondary
winding conducts, delivering a positive half-
cycle to the load.

31. Single-phase rectifiers:
FULL-WAVE RECTIFICATION
• The full wave rectifier produces twice as
many output pulses as the half wave
rectifier.
• average load voltage (i.e. DC output
voltage) is found as
Average DC Voltage for a Full Wave Rectifier

32. Multi-phase rectification
• The higher the number of pulses:
– the better the utilization of the rectifier
– the lesser the ripple amplitude
– the higher the ripple frequency — this implies that
filtering the ripple is easier.
• Systems with a number of pulses higher than 12
(normally obtained by combining two three-
phase bridges) are not often used since their
advantages are compensated by their growing
complexity.

33. Multi-phase rectifiers:
Three phase Half Wave Rectifier
• consists of a three
phase transformer
• a star connected
secondary three phase
transformer with three
diodes connected to the
three phases
• the neutral point ‘NTRL’
of the secondary is
considered as the earth
for the circuit and is
given as the negative
terminal for the load

34. • For each one-third of
the cycle, each diode
conducts.
• At the instant when
one diode out of three
is conducting, the other
two are left inactive, at
that instant their
cathodes becomes
positive with respect to
the anodes.
• Then the process
repeats for each of the
three diodes.
Multi-phase rectifiers:
Three phase Half Wave Rectifier

35. Multi-phase rectifiers:
Three phase Full Wave Rectifier
• also called as
a six wave half
wave rectifier
• in the figure
below the
diodes D1 to
D6 will conduct
only for ⅙ th of
the period, with
a period of

36. Multi-phase rectifiers:
Three phase Full Wave Rectifier
• the fluctuation
of dc voltage is
less in a three
phase circuit
• the variation
lies between
the maximum
alternation
voltage and
86.6% of this,