Motors dynamic braking

Dynamic Braking. When very quick or accmate stopping is not a necessity, the motor may be used to stop itself. AC motors can be dynamically braked by removing the ac power source and reconnecting a dc power source (supphed either from batteries or rectified ac power). The motor then acts like a dc generator with a short-circuited armatme. Energy is dissipated... 

Fan motors should be sized at 25% above the brake horsepower. Fans should be belt driven with variable pitch drives up to and including 25 FIP and fixed pitch drives at about 25 FIP. Fans must be radial and they must be balanced (static and dynamic) and mounted on anti-vibration supports. The connection of the fan outlet to the inside panels must be done by means of an internal flexible connector. 

Molecular systems that exhibit controlled or coordinated rotary motion are discussed in this chapter. These systems represent a reproduction of a variety of macroscopic mechanical devices on the molecular scale. From gears to a motor, passing through a turnstile, a brake and a ratchet, we describe their design, synthesis and dynamic behavior. The importance of molecular motors in the biological realm and possible applications in nanotechnology are also discussed. 

The brake horsepower for a fan may be computed in any of three ways, depending on whether the total change in head is mostly dynamic, static, or a mixture of the two. The corresponding nominal fan efficiency, iqf, is 40% for mostly a dynamic change, 60% for mostly a static change, and 70% for a mixture of the two. The power consumption is given by the following equation, which is similar to Eq. (16.16) and where the electric motor efficiency, can be taken as 90% ... 

Braking. Like ac motors, dc motors may be brought to a stop quickly by electromechanical brakes. Dynamic or regenerative braking schemes can also be used with dc motors. 

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