Page 236 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Control elements, accessories - layout of control cabinet

Objectives: At the end of this lesson you shall be able to:
• explain the layout marking methods and necessity
• state the methods of marking, cutting, drilling, fixing of accessories and components
• explain the methods of mounting and wiring the accessories
• state the various control elements used for control panel board
• list the different wiring accessories used in control panel wiring
• explain wiring of electrical 3 phase motor power and control circuit.

Introduction
Preparation of layout drawing and marking on control cabinet is very much essential, we must have a clear vision
of mounting components and their location on panel board/ control cabinet.

There is no such important method inpratice to make the layout on control cabinet. However a neat layout on
control cabinet is very much required.
The display and indicating instruments should be selected on the top position of the cabinet. Heavy and rare
operated devices such as fuse breaker etc; are to be fixed on the bottom of the cabinet.
The components and fixtures should have sufficient space in between to carryout future repair (or) replace
requirements. But too much space should not be provided, that will increase the size of the cabinet unnecessarily.
While finalising the layout plan the relevant IE rulers to be followed for better result.
Layout marking
Wiring diagrams for power and control circuit should be developed for sequence of operation of automatic star -
delta starter with forward and reverse. Types of protection, control, indication and measuring accessories needed
should be finalized.

To wire up the above starter in a control panel the well designed and easily understandable layout should be
finalized. Layout of the finalized wiring diagram should developed keeping important features of the control panel
in mind. While designing the control panel the outside dimensions, the swing area of cabinet doors and area
required for maintenance and tools kit have to be considered.
Control panel may be often used near the process area with high temperature, humidity and dust hence the
arrangement for cooling fan and dehumidifier along with filters and intake and exhaust vents should be needed.
Suitable size of control panel which can accommodate all the controlling, protective, measuring, indicating and
wiring accessories required for said wiring should be obtained or fabricated.
While selecting the control and protective accessories of the control panel the full load current of the individual
load, total load and duty cycle, simultaneous operation of the load and 25% additional load capacity of the motors
have to be considered.
The over load and short circuit protection may be given either ahead of the control panel by calculating the highest
rating of the branch circuit or individual motors depends on space available, cost factor and sensitiveness of the
operation.
The finalized layout may vary depends the individual design and mind application. However a sample layout
marking for the above starter is given in the Fig 1.
Once the panel layout is designed we must find out where and how to fit the accessories.
The finalized layout of accessories can be marked in the control panel using suitable marking device.

223

CITS : Power - Electrician & Wireman - Lesson 93-100