Basics of electrical control panel

It is useful for Electrical Engineers handling control panels and its designing works.

1. BASICS OF AN ELECTRICAL CONTROL PANEL P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 1

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 P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 2

3. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 3 The Main Components of a Control Panel Enclosure Incomer with handle and shaft Motor protection switch gear devices Indicators Push buttons Metering devices Cables Consumables

4. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 4 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 .

5. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 5 The selection of an enclosure is based on Dimensions of the Switch gear items inside in it. Material of construction 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

6. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 6 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

7. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 7 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.

8. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 8 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.

9. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 9 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.

10. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 10 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.

11. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 11 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.

12. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 12 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.

13. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 13 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 d amage through the use of over l oad heaters which is associated w ith the contacts of the contactor. If any over currents detects, t he contacts of the contactor changes from NC to NO, thus Protects the equipment.

14. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 14 Over L oad Relay Protects the circuit from over load condition with the help of Bimetallic strips which is attached w ith the trip mechanism. The rating of an overload relay is always expressed in a range. Eg : F or an over load relay LRD08, the current rating ranges from 2.5-4A.

15. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 15 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 e quipment.

16. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 16 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

17. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 17 Push Buttons Push buttons are used to On/Off the electrical equipment. Main Push buttons Green: Start Red : Stop Black: Emergency Stop.

18. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 18 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

19. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 19 Electrical Consumables Consumables includes nuts, bolts, washer, terminals, terminal markers, cable lugs, adaptors, lock nuts, spring washers etc.

20. P.O. BOX 261264, JEBEL ALI FREE ZONE, DUBAI, UAE 20