Stopping motors

Signs must be present with the words STOP MOTOR, NO SMOKING, and FLAMMABLE GAS. ... 

Red Stop Emergency Stop Stop motors Master stop... 

Figure C3.1.2. Stopped-flow apparatus with motor-driven syringes. Syringe plungers force tire reactants A and B tlirough a mixing chamber into a spectral cell. Kinetic data collection begins when tire effluent syringe plunger is pushed out to contact an activation switch, about a millisecond after tire initiation of mixing. (Adapted from Pilling M J and Seakins P W 1995 Reaction Kinetics (Oxford Oxford University Press)...

The electrons, Hberated at the anode, travel by electrical cable through the external load, such as an electric motor, to the cathode. If the external circuit is open the reaction is stopped, no fuel is consumed, and no power is generated. The electrolytic reaction, then, is controlled by the load connected to the cell. The overall fuel cell reaction is... 

Because of the very small bearing clearances in gas bearings, dust particles, moisture, and wear debris (from starting and stopping) should be kept to a minimum. Gas bearings have been used in precision spindles, gyroscopes, motor and turbine-driven circulators, compressors, fans, Brayton cycle turbomachinery, environmental simulation tables, and memory dmms. 

Motor-driven compressors usually operate at constant speed, and other methods of controlhng the capacity are necessary. On reciprocating compressors discharging into receivers, up to about 75 kW (100 np), two types of control are usually available. These are auto-matic-start-and-stop control and constant-speed control. 

Product Plastic pellets, Vn-in (3.2-mm) cubes, 30-lh/ft (481-kg/nd) hulk density equivalent length of system, 600 ft (183 m) f 1995 costs. Equipment includes motor and blower package, cyclone receivers, railcar-unloading connections, high-level interlocks for stopping the motor and blower combination when the silos reach a full level, and all necessary piping. Installation is not included. 

Magnetic motor starters are similar in function to manual starters except that thev are solenoid-operated, Thev are available up to 3730 kW (5()()0 hp). One of the main advantages is the convenience of electrical operation. Start-stop push buttons can be located anywhere, lien automatic or remote operation is needed, magnetic starters are essential. 

More importantly, such alloys also possess a very low temperature coefficient of electrical resistance (of the order of 220 idQ.IQ.rC, typical), which causes only a marginal change in its resistance value with variation in temperature. They can therefore ensure a near-consistent predefined performance of the motor for which the resistance grid is designed, even after frequent starts and stops. They are also capable of absorbing shocks and vibrations during stringent service conditions and are therefore suitable for heavy-duty drives, such as steel mill applications. 

In addition to electrical braking, a mechanical brake, as discussed in Section 6.20.1(A) may also be essential if the motor is required to be stopped completely because, at any value of excitation current, the motor will never reach a standstill condition. The heat of braking up to the standstill condition (N = 0) is roughly equal to one start and is expressed by equation (6.9). 

Due to excessive starting and braking heat losses it is not advisable to switch an induction motor ON and OFF frequently. The number of starts and stops a motor is capable of performing will depend upon its working conditions such as type of switching, braking and load demand etc. and can be determined from... 

But unlike a loom motor, which requires too many starts and stops, the operation of carding is continuous. Such motors are also required to have circular fins and a flat base or lug mounting as for loom motors. 

When thermal equilibrium is reached, the motor must be stopped as quickly as possible. Measurements must be taken both while the motor was running and after shutdown (wherever possible). No corrections for observed temperatures are necessary if the stopping period does not exceed the values given in Table 11.2. 

Table 11.2 Permissible stopping period of the motor after shutdown when it will reguire no temperature correction...

A stay put type stop push button may also be mounted near the motor for maintenance safety... 

The advantage of using frequency converters is that the possibility exists to use a ramp function when starting and stopping the motor (soft start). By using this function, it is possible to avoid starting both fans at full speed with closed dampers it also reduces stresses on the fan transmission (belts) at the start. 

These devices are tested only for internal explosions and not for external explosions pressurizing the devices from the outside. As an example, a factory-sealed push-button start/stop station connected to an explosion-proof motor starter cannot suffice as a seal for the motor starter conduit entry. A separate seal must be installed at the point of conduit entry. 

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