. Radiography, x-ray therapeutics and radium therapy . iple of the well-known commutatoremployed for dynamos and motors. This Fig. 1.—GaiflTe Rochefort outfit for alterna- rectifier is COUpled mechanically and elec-ting or continuouscurrent. For alternating trically with the motor, alternating in such supply there is a dmerence m the arrange- . ment of the interrupter. (Medical a manner that Commutation takes placeSupply Association.) -^ synchronism with the frequency of the alternating current. For instance, if alternating current is available havinga frequency of 50 cycles per second, the re


. Radiography, x-ray therapeutics and radium therapy . iple of the well-known commutatoremployed for dynamos and motors. This Fig. 1.—GaiflTe Rochefort outfit for alterna- rectifier is COUpled mechanically and elec-ting or continuouscurrent. For alternating trically with the motor, alternating in such supply there is a dmerence m the arrange- . ment of the interrupter. (Medical a manner that Commutation takes placeSupply Association.) -^ synchronism with the frequency of the alternating current. For instance, if alternating current is available havinga frequency of 50 cycles per second, the rectifier will give, in the sametime, one hundred continuous current impulses, or expressed scientffically,the rectifier is in synchronism with the alternating current. The commutation of the rectifier always occurs at the moment when thealternating current is at zero value, that is, at the moment of the change ofdirection. When working accurately this arrangement practically preventsthe generation of inverse current which is so harmful to the SINGLE IMPULSE APPARATUS Synchronism is obtained simply and absolutely by employing a rotaryconverter which is connected to a continuous supply, and which at the sametime supplies the alternating currentto the transformer and rotates therectifier which is mounted on the sameshaft. Alternating- Current High-tension Rectifier.—When using thealternating current, the current for thetransformer is derived direct from thesupply, the rectifier being driven by aself-starting single-phase synchronousmotor which takes the place of the con-verter. The outfits made for alternatingcurrent are smaller than for continuous,and these small outfits are withoutdoubt the best to use where ordinaryX-ray work only is required, that is notinstantaneous, as there is no troublefrom inverse radiation, no interrupterto synchronise, no rectifier to attendto, and no expensive rotary converter required.


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