Motor rotor critical

In continuous operation, rotor and windings asymptotically attain their permanent operating temperatures at different values Trotor, Tstator. For the steady state, a hotter rotor (compared with the stator windings), Trotor > T stator/ indicates a rotor critical motor, whereas hotter stator windings (compared with the rotor), Tstator > Trotor, indicate a stator critical motor. Normally, motors with a rated power exceeding 1. .. 2 kW, are rotor critical, smaller motors are stator critical. ... 

Another example is given in Fig. 6.59. A rotor critical motor (windings in thermal class F) is to be rated for T2 and T3 operation. The rotor (here, for simplification, considered as a thermal homogeneous component) passes the T3 class temperature limit (minus 5 K) after time tE3 at point 3, and somewhat later the T2 class or rotor temperature limit (+300°C minus 10 K) after time fEi at point 1. Meanwhile, the stator windings have passed the... 

Figure 6.59 Thermal behaviour of an F class rotor critical motor, stalled at tQ after steady state at rated power.

Rotor critical motors with temperature sensors in the rotor require expensive data transmission techniques, e.g. Pt 100 resistances, data convertor with frequency modulator, and brushless data transmission to a stator-fixed... 

LINUS (NRL) Election Beam Generator, Motor, Rotor (most critical maintenance item) None stated but probably 1-2 years 1 Rotor 1 Motor 1 E-Beam Generator Rotor - 6m O.D. X 12m long 535 tonnes 9 1) Repair of the rotor may be a very difficult operation. The slide seals are a major concern. 2) Hands on maintenance may be possible for motor and E-Beam generator... 

These estimates are frequently inaccurate because of second-order effects such as rotor saturation and harmonics. If the apphcation is at all critical, the motor manufac turer should be consiilted. 

At certain speeds, rotating masses become dynamicatty unstable and cause deflection and vibration in the rotor w hich may damage the motor. The speed at w hich such instability occurs is known as critical speed and occurs at different multiples of the rated speed. The masses must therefore rotate within 20T beknv or above the critical speeds to avoid such a situation. These vibrations settle down again at higher speeds above critical and recur at the next higher critical speed. 

Performance tests are those tests that need to be carried out on combined equipment such as a gas-turbine driven generator or a pump driven by a high-voltage motor. In such cases the dynamic relationship between the various equipments is of interest. For example, rotor vibration, critical speeds, run-up time to full speed, starting up and shutting down sequences, full-load and over-load performances, heat dissipation and cooling medium performance. 

By means of electron density maps on crystals of yeast mitochondrial ATP synthase, Stock et al. obtained the associated Fq- and Fi-motors, as demonstrated in Figure 8.27A. The Fo-rotor was obtained in sufficient detail to identify 10 c subunits and to locate the critical D61 residue that undergoes protonation/deprotonation of its carboxylate functional group. The small white spherical dots crossing the middle of the Fo-rotor locate the D61 residue in each subunit. 

By the hydrophobic consilient mechanism, the a-ATP sites provide a critical role of establishing a triangulation of repulsive forces that serves to limit the hydrophobic associations of the y-rotor. This triangulation of repulsive forces prevents the occurrence of a frictional drag on rotor rotation that would seriously limit motor efficiency. 

High-Accuracy Trip Curve Adjustments. Certain aspects of an overload relay s trip curves are critical for real motor protection. These include time-to-trip on locked rotor, motor overload conditions, and phase loss. 

Thermal overloads are hmited from approaching the ideal motor protection curves for these critical conditions. Because they do not directly measure current loading, but instead approximate it through use of heaters within the overload, they are subject to thermal overshoot (continued heat absorption after locked-rotor current is removed), residual heat remaining after reset, mechanical variables, and other difficulties in placing the various curves in optimum relationship with each other. 

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