Zero speed switches (ZSS) also known as Speed Actuating Sensing Switches are used to detect whether a

rotating Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

shaft is turning (even at very slow speeds) in various machines,

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power plants A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many pow ...

, and in industries involving the production of

cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...

, sugar,

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paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distrib ...

, etc. Zero speed switches mainly use

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, or magnetic proximity

technologies Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, science, ...

. Electromechanical speed switches are direct coupled, speed-indicating devices which open or close a set of contacts mechanically, as a function of the rotational speed of the switch shaft. Electronic zero speed switches are direct-coupled, speed-indicating devices that open or close a set of contacts through a relay and electronic circuit. User-defined settings and the rotational input speed of the shaft determine the speed at which an electronic zero-speed switch trips. A small timing delay may be required for avoiding nuisance tripping during running as well as during starting of the machine. This is taken care of in the electronics of the ZSS.

Specifications

Zero speed switches differ in terms of performance specifications, mounting styles, and features. Important specifications include operating range or the input shaft speed, trip set-point, operating temperature range, operating conditions, field adjustability, operating voltage, and relay contact rating. For various applications, zero speed switch suppliers can provide zero speed switches that are explosion proof, weather proof or

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proof. There are two types of ZSS, based on power supply provision. One is the interrupted power type, in which the power supply is given to the ZSS only for the duration for which the power is going to the motor of that machine. In the second type, the power supply is continuously given to the ZSS. Installation of the zero speed switches depends on the shaft or rotating part construction, where the speed has to be monitored.

References

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