Motors self-synchronous

Figure 10-16. Pneumatic digital to analog converter (motorized self-synchronizing regulator).

Remote indication or control may be obtained by the use of self-synchronizing motors, called synchro equipment. Synchro equipment consists of synchro units which electrically govern or follow the position of a mechanical indicator or device. An electrical synchro has two distinct advantages over mechanical indicators (1) greater accuracy, and (2) simpler routing of remote indication. 

The brushless DC motor (BLDC motor) is really an AC motor The current through it alternates, as we shall see. It is called a brushless DC motor because the alternating current must be of variable frequency and so derived from a DC supply and because its speed/torque characteristics are very similar to the ordinary with brushes DC motor. As a result of the brushless DC not being an entirely satisfactory name, it is also, very confusingly, given different names by different manufacturers and users. The most common of these is self-synchronous AC motor , but others include variable frequency synchronous motor , permanent magnet synchronous motor , and electronically commutated motor (ECM). 

When a generator is designed for a leading p.f. (in the underexcitation mode) it can operate as both a synchronous motor and a synchronous condenser. The machine is now self-starting and does not require a prime mover. 

A synchronous generator (and a synchronous motor) can be represented by many inductances and reactances to account for transformer-type induction, rotational induction, mutual coupling between windings, leakage and self-induction, magnetising and excitation induction and the effects of the pole-face damper windings. Extremely complex equivalent circuits have been developed for synchronous machines, see References 1 and 2 as examples. 

S) clironous motors range from subfractional self-excited units to large horsepower, dc-excited motors for industrial drives. In the single-phase fractional-horsepower range, synchronous motors are primarily used where precise constant speed is required. 

Like single-phase induction motors, synchronous motors cannot start themselves. They employ self-starting circuits. 

The mechanical secondary pump is of single centrifugal type with cavitation-free impeller, bottom entry flow to the impeller, sodium lubricated hydrostatic lower bearing and a synchronous drive motor cormected with the pump shaft by a cardan shaft with self-aligning couplings. 

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