Driver overload

For centrifugal and axial compressors, some form of override control is recommended for constant speed motor drivers to sense motor over load and override the process control until the cause of overload has... 

A driver selected to just handle the power requirements of the design point (other than maximum) is usually a poor approach to economy. Of course, there are applications wiiere the control system takes care of the possibilities of power overload. 

Axial or propeller blade fatis are eithet Irelt or gear driven. Some drivers are variable speed tnoiors. and some fatis have variable pitch blades. Iti s iecial circumstances, steam turbine, gas or gasolitie etigine drivers are used. Geais should be carefully specilied to avoid overload and should be special ) sealed to prevent moisture entering the case. 

For a solution, use 325 bhp for first stage. However, it is quite likely that either a 660 hp (overloaded) or a 750 hp driver may be available as standard. ... 

This is too hot an installation for V-belt drives. However, they may be used if ventilation is good and perhaps an insulated hot wall is interposed between the sheaves and fan housing. Allowance must be made for belt losses from manufacturers tables and also any other mechanical losses of the driver. If a motor is used, the shaft output should be 5 hp to cover losses and allow for nonoverload. The 0.2 overload at peak conditions does not justify a 7.5 hp motor because expected operations will be at 3.0, and a 5 hp motor can usually be overloaded 10% without difficulty. 

The laboratory scene in Fig. 1.2 (upper) caricatures a situation of extreme overload in a traditional laboratory devoted to high-throughput analysis. An increase in the demand for analyses often leads to the development of novel concepts, instruments, methods and procedures, increasing the capacity of the laboratory this in turn leads to a further increase in the demand for chemical assays, and so on. The synergistic chemical analysis/analytical chemistry dichotomy is often the driver for... 

The pump driver has to be rated for the maximum possible power draw. In the case of an electric motor (by far the most common choice), its protection will cause it to trip if overloaded, upsetting the process operation. Thus a pump with a non-overloading characteristic (and therefore downward sloping head curve) may be preferred for duties where the maximum flow is not easily limited, in order to lower the necessary drive motor rating. 

Tables 13-3 and 13-4 (below) list the common failure modes for fans, blowers, and fluidizers. Typical problems with these devices include (1) output below rating, (2) vibration and noise, and (3) overloaded driver bearings.

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