Document pzyEeV1z5598wZEDJ2G0e3NB

summer . POWERFAX 1 9 3S short periods. This type of motor has been unusually successful in handling these extremely heavy overloads in submarine practice. As a further explanation, or ex ample, of the ability of the com pensated machine to handle se vere loads withweak fields,--many years ago a considerable number ofstoragebatteryregulating boost ers of this type were built and in nearly every case the short peak overload required was enormously high. In one case, the load con sisted of unbalanced ore unloaders and the booster furnished for this work was rated at 1800 amperes with a guaranteed peak overload of 9600 amperes for 5 minutes. This machine was tested in the shops of the builders with over loads of 10,000 amperes for periods Fig. 5--VoUage regulation curie on an EUiott 1000-feu., 50-voU, 500-r.pjn. compensated generator. as long as 10 minutes with success ful commutation. The machine had an unusually long life for this clas3 maining constant under all speeds generally .where field weakening of of service, and when inspected af as long as the motor armature and the motor is combined with a ter 18 years of use the commutator field currents remain constant. In Ward-Leonard reversing system, was as perfect as when first built, mill work it is frequently desirable it is certainly advisable to use a and had every appearance of nev to speed up the motor beyond its compensated motor. er having been turned or even full-field, full-voltage condition. The adaptability of the com sandpapered. It is characteristic The generator can no longer be pensated machineiswellillustrated of storage battery boosters that depended upon to give this higher by its use for main driving motor speed, but by weakening motors onsubmarines. Here' the field of the motor it is easily motors of 1000- or 1200-hp. accomplished. It is quite custom rating carry frequent over ary to raise the motoryspeed as loads of three times their much as 200% in this^way. At normal rating these increased speeds, the normal with fields capacity of the motor remains at weakened to constant horse-power output, in less than one- asmuch as the decreasing field and third full mag increasing speed balance each oth netic strength, er to keep the output constant for a period of and the horse, power unchanged. half an hour at While it is possible to obtain a a time. Such a 3 to 1 speed range on a non-com- load is enor pensated type of motor, such a mously more machine is likely to commutate difficult to han very badly under heavy overloads dle than con with weak fields. Where loads of siderably heav Elliott 1000-hp., 6OCH0U, BOO- to 600-r.p.m. compensated direct- this kind are to be carried, and ier loads for current motorfor rolling mitt drioc. [121 CRIMDEBN00000371