PLC Based Protection Schemes for DC Drives Abstract: The drive industry witnesses an exhilarating growth to promote the sophisticated needs of the society. The inherent characteristics of DC motors suit most of the applications and forge to be a significant entity in the automated world. The protections of the drive units invite a serious attention to ensure their satisfactory operation. The growth of sensor technology along with the emergence of state of the art processors appear to corner the milestones and offer valuable options in this perspective. Inspect of the developments, still there is a far reaching scope to admonish greater facilities to predict and prevent the occurrence of different events that lead to the mal operation of the dc drive units. It is in this focus that the thesis proposes a PLC based protection scheme and envisages its investigative analysis for a series of contingences.
Introduction: 1. Basic philosophy of protection Protective circuits will protect the motor with, fuses, circuit breakers, overload relays, open field protection, over speed protection, current sensors and metal oxide varistors (MOV) for surge protection. 2. Need for protection in dc drives Protection commonly included in the Drive system to avoid harm due to mal operation and faults arise because of the followings: Short Circuit / Over current, Overload, Voltage Unbalance, Ground Fault Over current, Motor Over speed, Current Unbalance, under load, External Fault etc., 3. Reasons / Types of mal function in dc drives. 4. Existing preventive methods logics. Microprocessor based devise and controllers.
5. Need for new approaches. PLC’s are units of rugged design for an industrial setting and shield for improved noise immunity. Modular and Allowing easy replacement / addition of units
Objective: 1. To design schemes that attempt to a. Sense the VAR requirement at the supply side b. Over speeding of the drive motor and c. Short circuit fault at the...
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