Limit switch, electrical

Most electric motor actuators are equipped with limit switches, torque limiters, or both. Limit switches de-energize the electric motor when the valve has reached a specific position. Torque... 

Equipped with limit switches and/or torque limiters, the electric motor actuator has the capability of 0-100% control and has not only a motor but also a manual handwheel, and a clutch and gearbox assembly. 

LIMIT switches Q electric D pneumatic 45 MANUAL HAND PUMP... 

Many limit switches are the push-button variety. When the valve extension comes in contact with the limit switch, the switch depresses to complete, or turn on, the electrical circuit. As the valve extension moves away from the limit switches, spring pressure opens the switch, turning off the circuit. 

NO. OF RELAYsH time delay auxiliary LIMIT SWITCHES 0 ELECTRIC PNEUMATIC... 

In addition to the normal temperature control provided by refrigeration and heating systems, separate temperature alarms should be considered. Both low and high temperature limit switches can be connected into the facility alarm system providing a more reliable means of monitoring area temperature. Finally, emergency generators should be considered where electrical power is critical for temperature control and the primary source is not reliable. 

Following the invention of the transistor, for many years, they were made as individual, discrete electronic components and were connected to other electronic components (resistors, capacitors, inductors, diodes, etc.) on printed circuit boards to make an electronic circuit. The transistor s small size and low power consumption made it an ideal candidate to replace the bulky vacuum tubes then used to amplify electrical signals and switch electrical currents. These beneficial attributes of transistors made it possible for them to be used in making ever more complex electronic circuits in place of vacuum tubes. However, it did not take long before the limits of this approach of building circuits were reached. Circuits... 

Active valve electric motor operators and limit switches and pilot solenoid valves, will be seismically qualified by meeting the requirements of IEEE Standard 344. If the testing option is chosen, sine-beat testing must be... 

Demonstrating that the analysis be correlated with test data or be performed using standard analysis techniques. If the analytical option is employed for the qualification of valve electric motor operators, (or limit switches or pilot solenoid valves) the methods of analyses will be described in the FSAR. 

Control System. The operation of the reactor unloading mechanism is electrohydraulically controlled. The power that operates the mechanism is hydraulic. The flows in the hydraulic system are governed by soleiioid-operated valves. The valve solenoids are operated by push-button switches in. the various electrical control circuits. These circuits are interlocked by pressure switches, limit switches, and relays to ensure proper sequence of... 

Limit switches for hoists, electrical overhead travelling (EOT) cranes ... 

Prevent possibility of over travel (vertical as well as horizontal) of hoists and travelling cranes by providing limit switches for warning by alarms and by electrical tripping of the drive motors. 

Originally, die protection systems used only electromechanical sensors such as spring probes, microswitches, and pilot-operated limit switches. These sensors performed well enough in many applications, but they have drawbacks. Electromechanical sensors require contact with the part, tool, or strip, so they are subject to wear, and frequent adjustments are necessary to compensate. Some sensors, such as spring probes, rely on the part or strip to complete the electrical path to ground. Water-based (conductive) and petroleum-based (usually insulative) lubes can interfere with the operation of these sensors. Pilot-operated limit switches will effectively detect misfeeds, but not in time to stop the press before die closure. There are also some applications, for example, detecting small air-ejected parts, where it is impossible to use an electromechanical sensor. 

Subsystem Motor-Driven Power Wheel. The motor driven power wheel is mounted on the bridge assembly and functions as a caretaker of the electric cable. It provides automatic operation as it rolls up, or releases, the cable as required by crane travel. It is powered by a dripproof, brake-equipped AC motor protected by a limit switch. 

Subsystem Trolley Drive Assembly. The trolley drive assembly moves the hoist assembly laterally across the 14 ft span between the runway rails. This is accomplished by applying torque through the trolley drive gear case to the trolley wheels. The assembly consists of a 5-horsepower, 220/440-V, three-phase, 60-Hz enclosed motor, driving through the trolley drive gear reducer assembly. The motor is reversible and therefore able to drive the trolley in either direction. An electrically released, spring-set motor brake provides frictional torque to brake and hold the trolley. Contact limit switches are provided for trolley travel in either direction. 

A typical molding cycle will not start until a number of interlock conditions are satisfied. While the interlock conditions vary with the machine, the machine will not enter semiautomatic or automatic mode in the absence of these interlock conditions. Generally, the gate (operator guard door) must be closed and the gate safety (interlock) switches tripped. In hydraulic machines, the front gate has three switches (electrical, mechanical, and hydraulic) whereas the rear gate usually has one or more electrical limit switches. The electrical interlocks are usually electrical limit switches. When tripped, the hydrauHc interlock pre-... 

Today, infrared LEDs are used in a wide variety of applications, where they are typically paired with photodetectors. Infrared flux emitted by an LED source is transmitted a distance ranging from a few millimeters to many meters, and at the receiving end a photodiode or phototransistor detects the flux and converts it to an electrical signal. Silicon devices are most commonly used to detect the light emitted by Al Gai-xAs DH LEDs. Photodetectors made from In Gai-xAs are used with Ga Ini- AsyPi-y LEDs. Such emitter-detector pairs are used for the remote control of televisions and other consumer electronic products. Other applications for infrared LED-detector devices include intrusion alarms, blood gas analyzers, bar code readers, limit switches, and shaft encoders. 

High level makes electrical circuit and low-level breaks electrical circuit through a limit switch contact or the process liquid itself. This actuates (or stops) the transfer control valves (pnmps). Should not be directly installed on tanks with inflammable fluids. 

During reactor operation, the electric motor, the position sensors, the displacement pick-ups, and the limit switch sensors are energized. 

Install electrical limit switches OPEN add excess-flow valve at ready storage entrance set level indicator to shut off motor if 85% of total hquid level reached add overpressure relief to pump housing. 

IB/IIID Install electrical limit switches OPEN... 

Electrical equipment such as motors, pumps, blowers, and compressors should be operated whenever possible to assure proper rotation. Items such as control valves, interlocks, motorized valves, and limit switches should be checked wherever possible to ensure their... 

Electrical apparatus for signs of pitting or any deterioration of controller contactors, limit switches, and pushbutton stations and... 

Some modern equipment is complex and it may well prove to be too difficult for the ordinary electrician to find a fault and repair it. For example, if the photo-electric guard on a power press fails, the electrician can check the relevant limit switches and rectify a fault in them and can replace burnt-out lamps, but if the fault is in the electronic circuits, it will be necessary to call an electronics engineer, preferably from the maker. Unskilled tinkering with the electronic circuits or bypassing them to get the press back into production could have serious consequences for the press operator whose safety is dependent on the correct functioning of the guard. Where there is sufficient electronic apparatus to justify it, a specialist technician could be employed but otherwise specialist help should be sought. 

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