. Electric railway journal . ller Master Controller for for Direct Control Repulsion Motors switches are equipped with arc chutes and mag-netic blowouts, and are capable of interruptingvery heavy currents without severe burning. In-stead of the type of automatic overload circuitbreaker used with direct control, an overload relayis used which either opens the control circuit andtrips out all of the contactors, or unit switches, orelse trips a remote-controlled line switch. These systems have given highly satisfactoryservice, and their range of application is now suchas to cover many voltages an
. Electric railway journal . ller Master Controller for for Direct Control Repulsion Motors switches are equipped with arc chutes and mag-netic blowouts, and are capable of interruptingvery heavy currents without severe burning. In-stead of the type of automatic overload circuitbreaker used with direct control, an overload relayis used which either opens the control circuit andtrips out all of the contactors, or unit switches, orelse trips a remote-controlled line switch. These systems have given highly satisfactoryservice, and their range of application is now suchas to cover many voltages and motor sizes. Of latethe HL system has been still further simplifiedby reducing the number of groups and parts. Inits light-weight form it is being applied to light-weight cars, and in the heavier-weight forms it isrecommended by its manufacturer for general inter-urban car service. The MK system is now beingsuperseded to a certain extent by a later typeknown as PC control. 654 ] ELECTRIC RAILWAY JOURNAL [ Control Equipment. Schematic Control Diagram for 5000-Volt D. C. Equipment Indirect control systems for use in connectionwith high-voltage, direct-current motors are es-sentially the same as those used with lower main differences are in the greater amount ofinsulation, more powerful magnetic blowouts, in-creased creepage distances, and in the complica-tions sometimes necessary because the motors arerequired to operate at low voltage within the latter case, to insure the opening of thepower circuit, two switches that are connected inseries are generally used to make the interrup-tion. In connection with the control of alternatingmotors the only development of special interest isthe control for the doubly-fed motor adopted bythe Pennsylvania Railroad Company. This con-trol is an adaptation of the unit-switch system,and it is arranged for automatic acceleration. Themotors, which are connected in series, are startedand operated up to approximately 15
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