An electrical control panel contains electrical components that control and protect motors and equipment. It includes (i) an enclosure, (ii) an incomer switch, (iii) protection devices like circuit breakers, (iv) indicators, (v) push buttons, and (vi) metering devices. The selection of components depends on the power rating, supply, explosion rating, and application of the equipment. The enclosure holds the components and protects against environmental factors and electrical shock.

1. BASICS OF AN ELECTRICAL
CONTROL PANEL
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2. What is a Control Panel ?
• A cabinet which contains a collection of electrical
components designed to control and protect the
motors and equipments.
• The selection of components for a control panel is
mainly based on
1. Power Rating of the Equipment.
2. Incoming supply
3. Explosion proof category
4. Application of the equipment
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The Main Components of a Control Panel
i. Enclosure
ii. Incomer with handle and shaft
iii. Motor protection switch gear devices
iv. Indicators
v. Push buttons
vi. Metering devices
vii. Cables
viii. Consumables

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Enclosure
• The main visible part of a
control panel
• The purpose of an enclosure is
to hold and protect the
components from environment &
to prevent electrical shock to
equipment user’s.

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• The selection of an enclosure is based on
1. Dimensions of the Switch gear items inside in it.
2. Material of construction
3. Area of location of the panel.
Hazardous Area: Explosion proof panels with IP65/66
metallic enclosure
Non Hazardous Area: Non explosion proof panels with
IP54/55 metallic enclosure

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Incomer(Isolator) with handle & Shaft
• Isolator is an off load device,
used to control, protect and
isolate the equipment in case
of over current or short
circuit conditions.
• De energize the equipment
to allow the maintenance
in order to clear the faults

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How to select the current rating of an Isolator?
P = V x I x power factor
Where,
P – Rated power in Watts.
V – Voltage of the incoming supply.
I - Current flowing through the circuit.
Current, I = (P/(V x Power factor)) Amperes.
Isolator rating will be next biggest standard rating of the current
rating.
Eg: For our Aggreko skids (7.5kW, Duplex panel), we are selecting
63A isolator.

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Switch Gear components
• Combination of electrical components like MCCB,
MCB, Contactor, Over load relay, fuses, are used to
control, protect and isolate electrical equipment.
• The main function of these switch gear components
are to protect the electrical equipments in case of any
faults occurred in the system.

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MCCB(Molded Case Circuit Breaker)
• Provide protection to connected devices against both
over loads and short circuit
• The molded case provides an insulating
housing to mount all the circuit
breaker components.
• The position of the handle indicates
the status of the contacts whether
they are closed, open or tripped. So
faulted circuit can be identified easily.

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• MCCBs are inbuilt of Arc Extinguisher and Trip unit.
Arc Extinguisher
The arc formed due to interrupting the current flow is
confine and divide and thereby extinguishing it.
Trip Unit
In the event of a short circuit or prolonged over current, the
trip unit trip the operating mechanism with the help of a
temperature sensitive device and a current sensitive electro
magnetic device.

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MCB (Miniature Circuit Breaker)
• MCBs are automatically operated electrical switch used to
protect an electrical circuit from damage caused by over
current or over load.
• Basic function is to interrupt a current flow after protective
relays detect a fault.
• A fuse will operates once and
then must be replaced, but a
circuit breaker can be reset to
resume its normal operation.

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• MCBs can be operate only up to a rated current of 100A,
whereas MCCBs can be operated up to a rated current of
1000A.
• The operating mechanism of the MCB is attached with a
bimetallic strip, which is heated and bends in case of over
current flows through the MCB.
• During the condition of the short circuit, the electromagnet
attached with the MCB strikes the trip lever and causes an
immediate release of the contacts of the MCB.
• Provides protection to the electrical equipment as well as the
user who operates the electrical equipment.

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Contactor
• A contactor is a control device, used to pass/switch current
to an electric equipment.
• Electric equipments can be
protected from the over current
damage through the use of over
load heaters which is associated
with the contacts of the contactor.
• If any over currents detects,
the contacts of the contactor
changes from NC to NO, thus
Protects the equipment.

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Over Load Relay
• Protects the circuit from over
load condition with the help of
Bimetallic strips which is attached
with the trip mechanism.
• The rating of an overload relay
is always expressed in a range.
Eg: For an over load relay LRD08, the current rating ranges
from 2.5-4A.

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Phase Sequence Relay
• Continuously monitors all the phases
and detects phase sequence, phase
unbalance, phase failure and phase loss
in three phase systems.
• If phase sequence relay detects any
fault in the system, it automatically trips
the system and protects the electrical
equipment.

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Indicators
• Indicator lamps shows the
current status of the equipment.
Main indicators
• Red: R phase, Off
• Yellow: Y Phase, Trip
• Blue: B Phase
• Green: On

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Push Buttons
• Push buttons are used to On/Off the electrical equipment.
Main Push buttons
• Green: Start
• Red : Stop
• Black: Emergency Stop.

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Metering Devices
• Control panels are also equipped with metering devices like
Voltmeter, Ammeter and Hour run meters in order to find
Voltage, Current and speed of the equipment respectively

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Electrical Consumables
• Consumables includes nuts, bolts, washer, terminals,
terminal markers, cable lugs, adaptors, lock nuts, spring
washers etc.

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