SCRs are sensitive to high voltage, over-current, and any form of transients. For satisfactory and reliable operation they are required to be protected against such abnormal operating conditions. Because of complex and expensive protection, usually some margin is provided in the equipment by selecting devices with ratings higher (3 or 4 times hi
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gher) than those required for normal operation. But it is always not economi cal to use devices of higher ratings, hence their protection is imperative. High forward voltage protection is inherent in SCRs. The SCR will breakdown and start conducting before the peak forward voltage is attained so that the high voltage is transferred to another part of the circuit (usually the load). The turn-on of SCR causes a large current to flow and poses a problem of over-current pro tection. Over-current protection can be provided by connecting a circuit breaker and a fuse in series with the SCR, as usually done for the protection of any circuit. However, there are some reservations to their use. A semiconductor device is capable of taking overloads for a limited period, so the fuse used should have high breaking capacity and rapid interruption of current. There must be a similarity of SCR and fuse I2t rating without developing high voltage transients which endanger those SCRs in the off or infinite impedance condition. These are contradictory requirements necessitating voltage protection when fast-acting fuses are employed. Fuses when used, their arc voltages are kept below 1. 5 times the peak circuit voltage. For small power applications it is pointless to employ high speed fuses for circuit protection because it may cost more than the SCR. Current magnitude detection can be employed and is used in many applications. When an...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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