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The maximum voltage at the terminals of the dynamo(s) shall not exceed —— volts.
The dynamo(s) shall be of the latest and most efficient pattern; mounted on a base provided with an adjustable belt tightener, so that the belt may be tightened while in operation; capable of operating under full load for -- consecutive hours without increasing the temperature of any part, especially the armature, fields, and commutator, to such a degree as to endanger the insulation or decrease the efficiency of operation; shall have an insulation resistance of not less than -ohms between all parts insulated from each other; shall be adapted to operate at such speed as will allow the use of high-speed, automatic cut-off engines belted direct; shall be supplied with efficient oiling devices; the armature shall be balanced both electrically and mechanically so that there will be no tendency to spring the shaft, or to draw the armature toward either bearing so as to cause excessive friction and heating, and no vibration; all contacts, brushes, binding posts, etc., shall be so placed and protected that there is the least possible danger of receiving a shock; special attention shall be given to the proper securing of armature conductors to its surface; the dynamo(s) shall be so designed that the power required will be automatically proportioned to the number and the candle power of the lamps burning at any time, and shall be rated with such margin of
+ Sthey ,
will not be injured if
" subjected to a temporary overload of —- per cent. above such rating; if self-exciting, the coils furnishing the exciting current, and the commutator shall be so insulated and protected that it will be impossible under the ordinary conditions of operation to ground or cross them on themselves or on the armature circuit; if separately excited the exciting dynamo(s) also shall be subject to the general conditions given above, shall operate at a potential not exceeding –– volts, shall be of ample capacity to excite the fields of -dynamo(s) (each) having a capacity of ---, -- C. p. incandescent lamps, and shall operate with no appreciable sparking at the brushes.
45. Iustrile ments.
(See Note: p. 45, sec. 23.)
There shall be provided with each dynamo one ampère meter for indicating the current supplied by the dynamo; one voltmeter or pressure indicator which shall remain constantly in circuit so as to indicate continuously the pressure on the primary mains at the point to which it is connected, and shall be so constructed that the scale is plainly visible at a distance of at least ——; one insulating baseframe provided with rails and a suitable device for shifting the position of the dynamo
to alter the belt tension; one ground detector which shall continuously indicate the insulation maintained on both sides throughout the system; one pair of efficient lightning arresters; for the field-exciting circuit one hand regulator made entirely of incombustible material, one voltmeter, one brush jig, one double-pole knife switch mounted on an incombustible base, one double-pole fusible cut-out mounted on an incombustible base; if the fields are separately excited there shall be provided with the exciting dynamo one insulating baseframe as above, one endless belt, and also, if it excites the fields of more than one dynamo, one hand regulator for the field circuit of the exciting dynamo, one hand regulator for each of the field circuits of the excited dynamos, and one double-pole knife switch and double-pole fusible cut-out for each of the above field circuits, including that of the exciting dynamo unless lights are operated therefrom, in which case a switch and cut out shall be placed in the main circuit before branching off to the various dynamos.
There shall be provided the following num- 46. Converters. bers and sizes of converters: Number. Size.
- - lt. etc.
etc. Each converter shall reduce the voltage on the primary circuit to —- volts on the secondary circuit; shall have its capacity plainly
marked upon it; shall be provided with fuses on both the primary and secondary circuits; and shall be so arranged that when replacing fuses or otherwise working about the converter both the primary and secondary circuits niay be opened.
50. Summary. (See Note: p. 47, sec. 27.)
Each bidder shall fill out completely the fol-
above make . . . .
pulley at full load with no loss in
(See p. 48, sec. 28.)
There shall be placed upon this switch- 52. Switch board, in addition to the dynamo regulating atus and con i apparatus, such switches, cut-outs, and other appliances as are necessary for the proper and convenient manipulation of the circuits, such appliances to be named by each bidder in his proposal.
The appliances and connections shall be such as will permit the operation of any dynamo on any circuit or number of circuits, and the cutting in or out of any dynamo or circuit with certainty and rapidity without in any manner affecting the operation of other dynamos or circuits. They shall also be arranged in such manner as to render it impossible to connect two dynamos together by any arrangement of switches or combination of circuits. (For switchboard connections see secs. 30 and 31, p. 50.)
(See p. 51, sec. 32.)
Alternating Current or Direct Current Sys
tem, with the Parallel System of Distribu-
This contractor shall furnish, and, unless otherwise specified, erect the following apparatus and material: