The DC motor speed controller is built with a single phase semi-controlled thyristor bridge suitable for the control of the speed of independently excited DC motors by regulating the conduction period in open and closed loop. The DC motors are used in a wide variety of industrial drives, such as robots, machine tools, oil drilling rigs, mining, automotive systems, etc. The controller consists of three control loops: speed, current and armature voltage. Their speed can be easily adjusted in very fine increments ranging from standstill to rated speed and even above and their construction is made rather complex than their AC counterparts by the fact that they need acommutator, which reverses the direction of current and fluxes to produce a net torque.
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