Buchholz Relay | Buchholz relay – Principle of operation

In large oil immersed transformers, we can find a cylindrical object installed in the pipe connecting the conservator to the main tank. This cylindrical object, that looks like a solenoid valve is called Buchholz relay. It is a type of oil activated relays. It can be found in all oil immersed transformers rated higher than 500kva. (more…)

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PLC, DCS, RTU, SCADA and PAC Systems

PLC – Programmable Logic Controller

PLCProgrammable logic controllers are electronic devices used to control a process. It consists of CPU; Input and output devices, power supply, communication and redundancy units. PLCs are preprogrammed based on their application and put into operation. A PLC accepts inputs from the field, process the input based on the programming done and outputs the commands to the field equipment. It can also accept commands from the plant operators through SCADA and give commands to the field equipment. The features of PLCs vary from one manufacturer to the other but the basic architecture remains the same. (more…)

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What is meant by stalling of motor?

Stalling is a condition at which a motor stops rotating even when there is sufficient voltage at it’s terminals. This condition occurs when the torque required by the load is more than the maximum torque (Breakdown torque) that can be generated by the motor. At this condition, the motor drains the maximum current and the speed comes zero.

Induction motor Torque-Speed Characteristics
Induction motor Torque-Speed Characteristics

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