Current High starting

To meet the requirement of a high start-up torque and yet contain the start-up inrush current. 

Restriction in starting current and a requirement for high starting torque to accelerate heavy rotating masses sometimes limit the use of a squirrel cage motor. For such applications a slip-ring motor provides a better alternative. 

Use of wound-rotor induction motors has been largely in continuous-duty constant-speed supplications where particularly high starting torques and low starting currents are required simultaneously, such as in reciprocating pumps and compressors. These motors are also used where only alternating current is available to drive machines that require speed adjustment, such as types of fans and conveyors. 

Direct current motors are used for continuous operation at constant load when fine speed adjustment and high starting torque are needed. A wide range of speed control is possible. They have some process applications with centrifugal and plunger pumps, conveyors, hoists, etc. 

Standardized asynchronous motors are designed for operation on AC network current. That means they have high starting torque (current displacement grooves) and are trimmed for... 

When an experiment such as shown in Fig. 17M is conducted in solutions of increasing concentration of NaCl, the behavior shown in Fig. 19M is observed. The passivation current density is increased and the breakdown potential becomes less anodic until, at sufficiently high concentration, passivation can no longer be observed. Conversely, if NaCl is introduced into a solution in which iron is held in the passive region, nothing will happen at first, but after an induction period that depends, among others, on the concentration of Cl ions, the current will start to increase, and breakdown of passivity will be evidenced. 

A starting point for these new sensor functions is the adaptive cmise control system (ACC), which has already been introduced to the market. ACC systems monitor objects that are far in front of a vehicle and their relative speeds by either RF-radar (at 11 GHz) or laser-radar sensors. Due to the current high price of this system, the market will possibly be restricted mainly to luxury cars in the next few years. Volumes are expected to grow from several hundred thousand units in 2002 to a market of more than two million systems worldwide in 2005 [6]. 

As far as motors are concerned, the emphasis on hot surfaces, high starting currents and extended run-up times is not as great as with type e for Zone 1 areas, due to the inherently lower risk of hazard in a Zone 2 area. Special protective relays are not required and a system approach is not used. Similar design featmes in the mechanical part will be found e.g. clearances of fan blades, length of the air-gap between the rotor surface and the stator inner surface. Oil company specifications often call for non-sparking materials for the construction of the fans. 

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