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- FORWARD AND REVERSE MOTOR CONTROL DIAGRAM FOR CRANE FULL
- FORWARD AND REVERSE MOTOR CONTROL DIAGRAM FOR CRANE SOFTWARE
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Replace the converter module by a modern digital unit.Replace only the converter cubicle, if the motor is still in good condition.Replace the entire DC drive (converter and motor) by a new DC drive.Hence the choice between AC and DC technology is a difficult one and various options need to be assessed: When dealing with a legacy system based on DC drives, there is the question of whether it is worthwhile modernising an existing DC drive or less expensive to replace it entirely with an AC drive. Retrofitting and modernisation of existing installations Modern DC drives inherit the system integration flexibility more typical of AC drives. DC drives are also very effective for non-motor applications, such as electromagnets, charging batteries and electrolysis.
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Tough industrial applications, such as rolling steel and turning a cement kiln, are other areas where DC drives may be favoured. Unlike the AC drive, this regenerative braking is achieved without the need for intermediate storage, resistive dumping or an additional power bridge. The relatively small size of a DC drive, compared to an inverter drive, may also weigh in its favour.Ī standard 4-quadrant DC drive is able to motor and brake in both directions of rotation, with the energy generated under braking returned into the mains.
FORWARD AND REVERSE MOTOR CONTROL DIAGRAM FOR CRANE FULL
In many applications with overhauling loads, such as cranes and hoists, where the motor’s ability to hold full load at zero speed means mechanical brakes may not be required for control purposes, DC is often the most cost-effective and safely-controllable option. Permanent magnet and explosion proof DC motors are all also used. Wound field DC motors (series, shunt or compound) are used for coil feeding reels in milling/metalforming, crane hoists, motor-driven cable reels and elevator hoist motors.
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However, due to the very large legacy population of DC motors currently in use, especially of the wound field type, AC motors still represent only a small part of this industrial application. In cranes and hoists, as with many market sectors, there is a trend to employ AC motors with flux vector control. Regenerative 4-quadrant drives > 15 kW – DC drives usually less expensive.1-quadrant drives 40…60 kW – DC drives usually less expensive.Digital microprocessor-controlled power converter technology has now reached a level of technical sophistication which enables almost any drive job to be handled both with DC and AC drives.
FORWARD AND REVERSE MOTOR CONTROL DIAGRAM FOR CRANE SOFTWARE
Easy to use configuration and diagnostic software tools make setting up today’s DC drives quick and simple, and a range of networking and communications options are available. Meanwhile, at the other end of the scale, AC drives offer far greater bandwidth due to their higher carrier modulating frequency and the forced commutation of the IGBTs.īut in reality, modern DC drives are also at the forefront of variable speed drive technology. Of course, it is true that for simple, high volume applications such as the control of fans, pumps and compressors, AC variable speed drives are excellent and energy efficient. The AC motor, they argue, is simple and sturdy, does not need much maintenance, is therefore less expensive, and possesses a higher degree of protection into the bargain. It is often thought that DC technology equates to old technology, with many engineers adopting the simplistic view that the DC motor is complicated and requires a lot of maintenance, which makes it expensive to run. High-performance applications involving four-quadrant loads (Quadrants I to IV) where the speed and torque can be in any direction, include hoists, elevators, and hilly conveyors. Quadrant IV – Generating or braking, reverse braking – decelerating quadrant with negative speed and positive torque.Quadrant III – Reverse accelerating quadrant with negative speed and torque.Quadrant II – Generating or braking, forward braking – decelerating quadrant with positive speed and negative torque.Quadrant I – Accelerating quadrant with positive speed and positive torque.Andy Pye explains how they are incorporated into these systems.ĭrive applications can be categorised as single-quadrant, two-quadrant, or four-quadrant: For many decades, motors and drives have been utilised in electric hoists, reels and winches.