January 1, 1Q17.] 



THE INDIA RUBBER WORLD 



193 



Late Developments of Electrical Drives In Rubber Mills. 



/)'v tl'illiaiu //. Easton. Jl'cstinghousc Electric &■ Manufacturing Co. 



AS in most other lines of manufacturing, electric power is 

 coming to be widelj' used in rubber factories, for the in- 

 dividual electric motor to drive each machine has much 

 to recommend it. As a rule, rubber manufacturers prefer to gen- 

 erate their own- electric power, believing it more economical. 



Fig. 1. — High Volt.«lGe 100-Horse-power Motor Driving Two 

 Rubber W.\shees. 



owing to the fact that large quantities of steam have to be pro- 

 duced for vulcanizing purposes. But electrical engineers have 

 been able to convince several progressive rubber manufacturers 

 that even greater economy lies in another direction and that 

 there are also other attendant advantages. For instance, power 

 for a new and thoroughly modern factory recently erected for 

 the manufacture of automobile inner tubes is not produced at the 

 plant, but supplied by a central station. The advantages claimed 

 for this somewhat unusual service include the saving of the cost 

 of engines, generators, extra boilers and au.xiliaries ; the ability 

 to obtain power at any time, night or day. without the presence 



of the engine room force ; the assurance of more reliable power, 

 and lower operating costs. 



It would seem, therefore, that many rubber mills might adopt 

 such a system with benefit, and as the installation mentioned pre- 

 sents some interesting departures from ordinary usage, a descrip- 

 tion of its salient features may prove interesting. 



Alternating current at 2,200 volts is received from the central 

 station lines. Part of this current passes through transformers 

 and is reduced to a low voltage for lighting and operating some 

 small motors, but most of it is used at full voltage. Both high 

 and low voltage lines- lead to the main switchboard from which 

 tli.e power is distributed throughout the plant. 



The motors used in the first three steps of the process are all 

 applied in the same way and are similar in type. Each is a 

 Westinghouse 2,200-volt, alternating current, slip-ring motor, the 

 details being as follows : 



Machines Driven. 



Two 16 X 24-inch Birmingham washers. 



Three 20 .\ 50-inch Birmingham mills. 



Two 20 X SO-inch Birmingham warming mills. 

 .-\ 75-kilo\vatt Westinghouse direct-current 

 generator for supplying cunent to the cal- 

 ender motor. 



It will be noticed that these motors are of the same voltage 

 as tlie Central Station lines. If motors of lower voltage had 

 been selected it would have been necessary to install trans- 

 formers, but under the circumstances this expense is avoided. 

 As can be seen from the illustrations, these motors are all en- 

 closed by wire netting so that there is no danger of unauthorized 

 persons coming near them. 



Slip-ring motors are used instead of squirrel-cage motors, 

 because a squirrel-cage inotor in starting ponderous machinery 

 of this kind draws a very heavy current from the line ; but with 

 a slip-ring motor the starting" current can be kept down to very 

 nearly the full load value. The motor is started with resistance 

 in the rotor circuit, which is cut out gradually by means of a 

 drum controller as the motor speeds up. The drum controller 

 and resistance handle only the low voltage rotor current. An 

 oil circuit breaker connects the motor to the high voltage line 

 and automatically disconnects it in case of an overload. 



In order to stop the washers and mills quickly in case of emer- 

 .gency. each machine is equipped with a Cutler-Hammer inag- 

 netic clutch and brake. Safety switches are located convenient 



Fig. 2. — Ge.\er.\tok .Sui'PL'i i.xg Calk.xdkr AIutc/k; Also 2UH-Him.sK-i'uwKK .Muhik Dkivi.xc; Two \\'arming Miixs. 



