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A limit switch with a roller-lever operator; this is installed on a gate on a canal lock, and indicates the position of a gate to a control system A limit switch mounted on a moving part of a bridge In electrical engineering , a limit switch is a switch operated by the motion of a machine part or the presence of an object.
The key can then be used to unlock the kiln door. While the key is removed from the switch interlock, a plunger from the interlock mechanically prevents the switch from closing. Power cannot be re-applied to the kiln until the kiln door is locked, releasing the key, and the key is then returned to the disconnecting switch interlock. [1]
Part of a ladder diagram, including contacts and coils, compares, timers and monostable multivibrators. Ladder logic is widely used to program PLCs, where sequential control of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems or for reworking old hardwired relay circuits. As ...
Elevators with more than 30 m (98 ft) of travel have a system called compensation. This is a separate set of cables or a chain attached to the bottom of the counterweight and the bottom of the elevator cab. This makes it easier to control the elevator, as it compensates for the differing weight of cable between the hoist and the cab.
In many cases, it is possible to design a relay logic diagram directly from the narrative description of a control event sequence. In general, the following suggestions apply to designing a relay logic diagram: 1. Define the process to be controlled. 2. Draw a sketch of the operation process. Make sure all the components of the system are ...
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A governor, or speed limiter or controller, is a device used to measure and regulate the speed of a machine, such as an engine.. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor on a reciprocating steam engine, which uses the effect of inertial force on rotating weights driven by the machine output shaft to regulate its speed by altering the input flow ...
Typically, the voltage is controlled by reverse-parallel-connected silicon-controlled rectifiers , but in some circumstances with three-phase control, the control elements can be a reverse-parallel-connected SCR and diode. [2] [3] Another way to limit motor starting current is a series reactor. If an air core is used for the series reactor then ...