Showing posts with label protection. Show all posts
Showing posts with label protection. Show all posts
Thursday, January 9, 2014
Over voltage Protection Circuit Diagram
This is a Over voltage Protection Circuit Diagram. A silicon-controlled rectifier is installed in parallel with the 12-V line and connected to a normally-closed 12-V relay, K1. The SCRs gate circuit is used to sample the applied voltage. As long as the applied voltage stays below a given value, SCR1 remains off and Kls contacts remain closed, thereby supplying power to the load.
When the source voltage rises above 12 V, sufficient current is applied to the gate of SCR1 to trigger it into conduction. The trigger point of SCR1 is dependent on the setting of R1. Once SCR1 is triggered (activating the relay), K1s contacts open, halting current flow to the load.
Over voltage Protection Circuit Diagram
Wednesday, May 15, 2013
Practical Example Of Bus Bar Protection
Assume the following system shown in the figure which consists of two bus bars and four equipments two on each bus and a bus coupler between the two buses.
Each equipment contains one current transformer. Connected on it except the bus coupler which contains two current transformers one on each side of the circuit breaker. For equilibrium, each bus is stable in load condition (without faults).
There are two cases:-
1- Case bus coupler is disconnected: 2- Case2 bus coupler is connected
I3+ I4=0 I1+ I3+I4=0
I5+ I6=0 I2+ I5+I6=0
Note:
CT1 (of the coupler) is connected between circuit breaker and bus1 and for equilibrium it is added to CT3, and Ct4 which are connected to bus2, and CT2 (of the coupler) is connected between circuit breaker and bus2 and for equilibrium it is connected to CT5, CT6 which are connected to bus1.
The advantage of these connections is to protect the zone between circuit breaker and current transformer of the coupler. If one CT is installed for the coupler, the zone between circuit breaker and current transformer is not protected by bus protection.
Friday, April 12, 2013
Simple OBD Vehicle Protection
vehicle immobilisers are fitted as standard to modern cars and heavy goods vehicles. Anti-theft mechanisms have become more sophisticated but so have the methods employed by crooks. Nowadays once the thief has gained access to a vehicle they will most likely use an electronic deactivation tool which seeks to disable the immobiliser, once this has been accomplished a blank transponder key/card can be used to start the engine. In many cases communication with the immobiliser is made using the OBD-II diagnostic connector.
Although the OBD-II protocol itself does not support the immobiliser, the vehicle manufacturer is free to use the interface as neces-sary for communication, either the standard OBD-II signals or unused pins in the OBD-II connector (i.e. those undefined in the OBD-II standard). Using one of these pathways the immobiliser can usually be electronically disabled.
OBD Vehicle Protection Circuit Diagram
This may be unsettling news for owners of expensive vehicles but when professional car-thieves call, armed with the latest OBD-II hacking equipment this simple low-cost low-tech solution may be all that you need. The idea is ver y simple: if all connections to the OBD-II connector are disconnected there is no possibility for any equipment, no matter how sophisticated to gain access via the vehicle’s wiring.
The OBD-II connector is usually locate d underneath the dashboard on the passenger side; once its wiring loom has been identified a switch can be inserted in line with the wires. The switch should be hidden away some-where that is not obvious. In normal opera-tion you will be protected if the vehicle is run with the wires to the socket disconnected. Make sure however that you throw the switch reconnecting the socket before you next take the vehicle along to a garage for servicing or fault diagnosis.
The diagram shows the ISO K and ISO L wires switched. To cover all bases it is wise for every wire to the socket is made switchable except the two earth connections on pins 4 and 5 and the supply voltage on pin 16. Almost ever y vehicle manufacturer has their own method of vehicle immobilisation, by disconnecting every wire it ensures that no communication is possible (even over the CAN bus). Now the innermost workings of your vehicle will be safe from prying eyes. When a hacker plugs in a deactivation tool it will power up as normal but probably report something like ‘protocol unrecognised’ when any communication with the OBD port is attempted.
Author : Florian Schäffer - Copyright: Elektor
Friday, April 5, 2013
Lightning Protection ELCB
Lightning Protection ELCB (CIRCUIT BREAKER Earth Leakage)
Installation of a building usually equipped with a safety short circuit current and current limiters. In the event of a short-circuit the safety fuse will break, and when the series occurred over the current-limiting load (MCB) will open the circuit so that circuit current flow to the inside of the building to be disconnected.
If it occurs in an electrical installation safety is a leakage current and current-limiting fuses can not provide security so that the power loss will occur continuously. Apart from that, if there are power users have a leakage current and untouched by humans, the safety will not be decided so that the electrical circuit is quite dangerous it would be safe if the installation is already installed grounding.
But when man-voltage electrical power users then all these safety devices can not be secured. For that installed a safety device, called an Earth Leakage Circuit Breaker or ELCB. This tool is able to decide the relationship string of leakage current in the event of 30 MA in a time of 0.1 seconds. Leakage current is intended to be through electrical components in the normal state of no voltage or phase conductor directly touched by humans.
How it Works chain of ELCB
ELCB separate chain consists of a magnetic coil and switch. This switch can be manually controlled electric and magnetic fields. If the position of liaison ELCB switch is closed, then the source voltage will flow gets the load. Magnet coils which will open the circuit to work when there is an electric current flowing in the coil. Magnet coil circuit that will open, works when there is an electric current flowing in the coil. ELCB magnet coil also called z. Travo, which normally do not get the voltage. If there is leakage current is z. Travo will work to open the circuit by pulling the main chain of the switch should be set up in advance for reuse and so on.
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