AC drive systems

These AC drive systems require the inverters to operate with either low-slip induction motors or reluctance-type synchronous-induction motors.. Such systems are u.sed where DC commutator motors are not acceptable. Examples of such applications are motor operations in hazardous atmospheres and high motor velocities. 

Before 1990s, thyristors and transistors were used as power modules for AC drive systems. Since then other semiconductor switching power modules have been used, such as GTO, MOSFETs, IGBTs, and combination of them. Nowadays IGBT and MCT-based inverters are used by electric drives manufacturers for the electric car market. The key characteristics of the different types of technology used for power electronic component are reported in Table 5.1. However, other power switching modules are currently under development [12]. 

A complete discussion of the benefits of modern electrical systems over their predecessors is out of the scope of this paper. However, several major benefits of modern AC drive systems will be briefly outlined. A modern AC drive system is capable of being operated at unity power factor, or even leading power factor to provide power factor correction to the remainder of the hoist plant. The performance is far superior to previous DC drive systems whose power factor is dependent on speed, ranging from 0.1 to 0.8 during a typical duty cycle. The improved power factor will result in significant savings in electricity cost, and in power factor correction equipment that may otherwise be required. 

Modern AC drive systems intrinsically produce less hcumonics than traditioncd DC drive systems, and can usually meet IEEE-519 requirements without the need for external active filtering equipment, and without the risks of system resonance. 

The two AC drive systems used on extruders are the adjustable transmission ratio drive and the adjustable frequency drive. The adjustable transmission ratio drive can be either a mechanical adjustable speed drive or an electric friction clutch drive. 

Miyazaki, S., Kurosawa, R. and Ben-Brahim, L. US Patent Number 5502633, 26 March 1996 www.ess-sih.ru/MANUAL/Tosvert mv t.pdf Toshiba AC Drive System, Medium Voltage Inverter ... 

Inverter-AC Motor Drives. An adjustable-frequency control of AC motors provide efficient operation with the use of brushless, high-performance induction, and synchronous motors. A typical system is shown in Figure. 3-14. Such a system consists of a rectifier (which provides DC power from the AC line) and an inverter (which converts the DC power to acljustable-frequency AC power for the motor). Inverter cost per kilowatt is about twice that of controller rectifiers thus the power convertor for an AC drive can approach three times the cost of a DC drive. 

AC vector motors typically operate with a power factor In the range of 0.90 to 0.98 [20]. The power factor for a DC drive system can be considerably lower and as low as 0.5. Replacing an older DC motor with an AC vector motor can be economically attractive due to an Increase In both the efficiency and the power factor. 

David Finney, Variable frequency ac motor drive systems. Peter Peregrinus Ltd (1991). ISBN 0 863-41114-2... 

Mine hoist drive systems have evolved from DC-based systems to AC systems in the majority of new apphcations. Early AC apphcations involved the use of cycloconverter drive systems, however the trend in modern hoisting systems is to utihze cage induction motors on many new installations coupled with Pulse Width Modulated (PWM) style Vcuiable frequency drives (VFDs) complete with Active Front End (AFE) technology. 

The AC drive reduces the RMS kVA demand by converting incoming power at unity power factor. However, the power system is still subject to a high peak demand at the end of the acceleration phase of the hoisting cycle. By reducing the acceleration at the end of the acceleration phase of the duty cycle, the peak power (and kVA) demand is reduced. Various algorithms can be applied. In the example above, the acceleration rate is reduced at 90% of full speed, for... 

Ingedrive MV100 A Medium Voltage and Full Power Redundant AC Drive for Driving the Tongting Mine Hoist System... 

The hoist drive solution presented in this work, which is based on the Ingedrive MVlOO medium voltage AG frequency converters, contains two completely independent Active Front End Rectifier and Inverter sets under the well-known AC-DC-AC topology. The entire drive system solution allows the operation at full speed and full load (then full hoist performance, with no limitation) even in the case that one frequency converter (AG-DC-AC set) is unavailable. The solution presents some extra benefits comparing to the original hoist system solution that was based on two slip ring rotor wound induction motors in which the speed control... 

The hoist was supphed with a high voltage AC PWM drive, coupled to a 76.4 rpm overhung synchronous motor. A pony drive was provided to allow controlled movement of the hoist should personnel become stranded in the shaft on a conveyance during maintenance activities, due to a power outcige or fculme of the main drive system. 

A DC drive system with a tachometer feedback is preferred for fiber drives, although AC drives with an inverter have acceptable accuracy and are preferred for controlling fans with... 

The ACS controls the system. Nine of 12 control drums located in the reflector are controlling members and are actuated by one automatic control (AC) drive located behind the radiation shielding. 

In Europe, the drive system of the Impact propelled the Opel Impuls2, a conversion vehicle based on the Opel Astra Caravan in 1991. A new, specifically developed AC induction drive unit with IGBT inverter technology was used to build a small fleet of Impuls vehicles see Figure 8.4). The fleet served as an automotive test bed for the integration of various advanced battery systems such as nickel-cadmium, nickel-metal hydride, sodium-nickel chloride, sodium-sulfur, and sealed lead-acid. 

FC Hybrids in 2004-2006, the Alameda Contra Costa Transit (AC Transit) and SunLine Transit (serving the Palm Springs, California, area) demonstrated 40-foot Van Hool buses using UTC Power s FC stacks and compressed hydrogen fuel integrated with an ISE hybrid electric drive system. 

The use of an adjustable-frequency power supply (ac inverters) in conjunction with the induction motor results in an adjustable-speed drive system.The speed of the motor is adjusted by controlling the output frequency of the ac inverter.Thus the induction motor can be used on many adjustable-speed apphcations. The speed-torque motor performance at different input motor frequencies is Ulustrated by Fig. 5.127a. This permits the apphcation of induction motor adjustable-speed systems to loads such as fans and pumps for flow control with considerable power savings over fixed-speed systems with dampers or valves for flow control. Figure 5.127Z) shows the performance of a 10-hp motor adjustable-frequency system driving a fan load. 

The drive system has a frictionless asynchronous AC motor and inductive position sensor. The ranges are listed, accuracy is better than +10% at 0.00002 mN-m. 

Conventional back-drive systems on decanters perform a braking duty. As such many of them have the ability to regenerate power. Although an eddy current brake is unable to do this. AC. DC. and inverter motors, and hydraulic systems are. The braking process causes the electric motor to act as a generator and so returns power to the grid. In the case of the DC and inverter motor, the power regenerated is usually considered dirty unless electric filters are fitted which smooth out unwanted harmonics. 

Toyota Motor Corporation has also been developing zinc/bromine batteries for electric vehicles. - A concept urban transportation vehicle, called the EV-30, has been designed for use with Toyota s zinc/broinine battery and has been displayed at motor shows in Japan. This two-seater vehicle would transport people in buildings, shopping centers, small communities, and to and from train stations—a horizontal elevator concept. The front-wheel-drive system uses an AC induction motor built by Toyota Motor Corporation. The battery system is modular zinc/bromine at 106 V and 7 kWh. 

Ribeiro, R.L.A., Jacobina, C.B., da Silva, E.R.C., Lima, A.M.N. Faulttolerant voltage-fed pwm inverter ac motor drive systems. IEEE Transactions on Industrial Electronics 51(2), 439-446 (2004)... 

Single screw extruder drive systems While extrusion drive systems have evolved and can maintain speeds within 0.1%, the recent trend toward AC drives is being driven primarily by improvements in reliability and cost and not for better controls. The primary role of the drive system has remained the... 

The initial pilot plant agitation system was powered by a 40-kW AC motor with a standard gearbox. A problem with AC drives is that they do not deliver full power below 10 rpm. In the situation where the processing conditions produce a tacky material the rotational speed falls to below 10 rpm and the system does not... 

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