Current Sensing of Electrical Drives: Current Sensing of Electrical Drives is required for the implementation of current limit control, inner current control loop of closed-loop speed control, closed-loop torque control of a dc drive, for sensing fault conditions, and for sensing speed in dc drives by back emf sensing method. In order to avoid interaction […]
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Closed Loop Speed Control of Multi Motor Drives: When mechanical part of the load is of large physical dimension it becomes desirable to share the load between several motors. For example a rotary printing press usually has several printing stations which are mechanically coupled by a long drive shaft. Each section (printing station) is driven
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Closed Loop Torque Control of Drives: Closed Loop Torque Control of Drives scheme of Fig. 3.4 finds application in battery operated vehicles, rail cars and electric trains. Driver presses the accelerator to set torque reference T*. Through Closed Loop Torque Control of Drives, the actual motor torque T follows torque reference T*. Speed feedback loop
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Current Limit Control of Drives: Current Limit Control of Drives scheme of Fig. 3.3 is employed to limit the converter and motor current below a safe limit during transient operations. It has a current feedback loop with a threshold logic circuit. As long as the current is within a set maximum value, feedback loop does
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Speed Control and Drive Classification: Speed Control and Drive Classification are the Drivers where the driving motor runs at a nearly fixed speed are known as Constant Speed or Single Speed Drives. Multi-speed drives are those which operate at discrete speed settings. Drives needing stepless change in speed and multispeed drives are called Variable Speed
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Modes of Operation of Electrical Drive: Three types of Modes of Operation of Electrical Drive: Steady-State Acceleration including starting Deceleration including stopping As we know already, steady-state operation takes place when motor torque equals the load torque. The steady-state operation for a given speed is realized by the adjustment of steady-state motor speed-torque curve such
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Load Equalisation in Electrical Drives: Load Equalisation in Electrical Drives – In some drive applications, load torque fluctuates widely within short intervals of time. For example, in pressing machines a large torque of short duration is required during pressing operation, otherwise the torque is nearly zero. Other examples are electric hammer, steel rolling mills and
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Steady State Stability of Drive: Equilibrium speed of a motor-load system is obtained when motor torque equals the load torque. Drive will operate in steady-state at this speed, provided it is the speed of stable equilibrium. Concept of Steady State Stability of Drive has been developed to readily evaluate the stability of an equilibrium point
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Time and Energy Loss in Transient Operations: Starting, braking, speed change and speed reversal are transient operations. Time and Energy Loss in Transient Operations can be evaluated by solving Eq. (2.19) along with motor circuit equations. When T and TL are constants or proportionals to speed, Eq. (2.19) will be a first order linear differential
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Classification of Load Torques: As we know already, the nature of Classification of Load Torques depends on particular application. A low speed hoist is an example of a load where the torque is constant and independent of the speed (Fig. 2.3). At low speeds, windage torque is negligible. Therefore, net torque is mainly due to
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