Stator 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. ... 

Figure 6.58 Thermal behaviour of an E class stator critical motor, stalled at to after steady state at rated power.

Temperature sensors as an alternative to or associated with current dependent protective devices are within the scope of e standards. Temperature measurements in stator windings are commonly used, but as an alternative to current dependent protective devices they are applicable in stator critical motors only. 

Nevertheless, whenever the rotor is more critical, despite a higher rotor operating temperature, rotor thermal curves are provided by the manufacturer for facilitating protection for the rotor also through the stator. 

Seals are very important and often critical components in turbomachinery, especially on high-pressure and high-speed equipment. This chapter covers the principal sealing systems used between the rotor and stator elements of turbomachinery. They fall into two main categories (1) noncontacting seals, and (2) face seals. 

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... 

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... 

Liquid-liquid emulsification is a critical step in the double-emulsion mieroencapsulation proeess (W/OAV or OAV/O). It was found that the size of these droplets decreases with inereasing homogenization intensity and duration. The emulsion droplet size depends as expected on viscosity, total volume size, and volume ratio of the continuous phase to the dispersed phase the rotor/stator design was also investigated. All these physical parameters influence the structure of the microspheres obtained by this technique. 

The values of predicted from Equations 9.23 and 9.28 are within 6.6%, indicating that the basic criterion for critical speed is relatively simple and the difference between different impeller designs is mainly due to the energy/pressure losses suffered in the impeller/stator region. 

One example of this type of application is a rotary switch for military radios. Here LCPs were chosen to replace a diallyl phthalate (DAP) thermoset for the stator to solve the problem of high reject rates. Close tolerances down to 0.025 mm must be held on critical areas of the moulding, and the ability to mould thin-walled sections is essential. 

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