Motor drive solid-state

A variety of AC and DC drives are available for extruders. DC motors with solid-state eontrollers and power supplies provide the most flexible seenario for control. A speed control feedback loop on the drive will minimize variation in the extruder output. The unwind roll should be equipped with a tension control device such as an electronic regulator. 

Tbe use of special motors was more relevant until the 1980s. when solid-state technology was still in its infancy and wa.s not so widely applied. With the advent of static drives, as discus.sed in Sections 6.2-6.4, the use of standard motors is gradually becoming more common for all these applications. The drive it.self can alter the supply parameters to the required level to make a standard motor operate and perform within desired parameters, besides conserving energy. The purpose of describing a few of these applications is only to indicate their non-standard features, where a standard motor with normal controls may not be able to perform the required duties. 

Solid-state microprocessor based these are more sensitive and accurate. They can be made digital to be connected to a computer for remote monitoring and control of the process that the motor is driving. 

Wound-Rotor Motor Drives. The wound-rotor induction motor, using adjustable rotor-circuit resistance, is rarely used. However, two versions that use solid-state auxiliary equipment are finding limited application. 

Solid-State DC Drives. The controlled-thyristor rectifier and separate-field DC motor is the solid-state motor drive in greatest use. The combination provides control over at least a 10 1 speed range, plus an additional two to three times by field weakening. Depending upon the power level, the rectifier is operated directly from the AC supply lines, or via a transformer. Typical speed regulation of 2% can be accomplished with a single control system. The horsepower and speed limitations are set by the DC motor, not by the semiconductor rectifiers. The DC motor and rectifier can be combined to any required power level. 

Commercial solid-state DC motor drives fall into three general groups. Drives operating from single-phase lines are available in fractional horsepower sizes up to about 3 hp. Three-phase drives are available in horsepower sizes from 5 to 500 hp. Drivers above 500 hp are generally classed as special. 

The experimental rig is mounted on an optical bench, along which it can be moved. This ensures that the diffracted intensity is maximised by locating the ideal alignment of the diffraction lozenge and the sample (Fig. 4). The position of the solid-state detector is controlled by a series of motors which drive it remotely to the required angle. 

Variable Frequency Drives. An important energy by-product of solid-state electronics is the relatively low cost variable speed drive. These electronic devices adjust the frequency of current to control motor speed such that a pump can be controlled directly to deliver the right flow without the need for a control valve and its inherent pressure drop. Figure 11 shows that at rated load the variable speed drive uses only about 70% as much power as a standard throtde control valve system, and at half load, it uses only about 25% as much power. 

The specific power of rare earth permanent magnet motors can exceed 1 kW/kg. The combination of reliable, low-cost, solid-state controllers and brushless permanent magnet motors will find applications in (i) computer accessories like disk drives, printers, x-y plotters, (ii) consumer goods like hand tools, fans, and air-conditioners, (iii) robotics, traction motors, steel mills, lift motors, and (iv) aerospace flight control actuators. 

DC drive (direct-current drive) n. A machine drive, particularly that of an extruder, powered by a direct-current motor. The availability of economical solid-state rectifiers, and the good torque-versus-speed characteristic and tight speed regulation of DC drives have made them the most popular choice today for variable-speed service. 

Solid-state controls n. Control instruments or motor-drive controls whose circuitry employs transistors and kindred elements rather than mechanical or vacuum-tube devices. Practically all modern process instruments are of this type. 

Electrical building - houses the two non-safety-related standby diesel generators and their associated auxiliary equipment, and the solid-state adjustable speed drive units powering the feedwater pump motors and others powering the Reactor Water Cleanup/Shutdown Cooling System pumps. 

The decision logic is made up of solid-state circuitry that compares with various inputs. When a combination of inputs requires action, the logic circuitry provides a signal that seals into turn on a solid-state power gate that operates activation devices, such as contactors, circuit breakers, and solenoid pilot valves. Actuation devices in turn control power to the motors that operate valves and drive pumps, or control the air supply to pneumatically operated valves. 

Some early DC extruder drives used fixed-speed AC motors to drive DC generators that produced the variable voltage for the DC motor. Nowadays, the DC motor drives usually operate from a solid-state power supply, since this power supply is generally more cost-effective than the motor generator set. The DC motor drive can be simpler and cheaper than the variable frequency drive, even when the higher cost of the DC motor is included. The smaller number of solid-state devices tends to give the DC drive a better reliability than the variable frequency drive. Brushes and commutator maintenance is the principal drawback to the use of DC motors. If the drive has to be expiosion-proof, the additional expense associated with this option may be quite iarge for a DC drive, more so than with a variable frequency AC drive or a hydraulic drive. A schematic of the DC drive is shown in Fig. 3.4. 

The DC voltage from the solid-state power supply generally has a rather poor form factor. The magnitude of the form factor is dependent on the configuration of the rectifier circuitry. The poorer the form factor, the higher the ripple current in the DC motor. This increases motor heating and reduces the power efficiency. Several three-phase rectifier circuits are available for the AC line power into DC. Most drives over 5 hp use three-phase full wave circuitry. Figure 3.5 shows a three-phase half-controlled full wave rectifier. 

Variable Speed Motor drives—Above 1/4 HP, solid-state variable frequency AC motor drives are preferred to solid-state variable voltage DC motor drives. Below 1/4 HP stepper motor drives are preferred to variable voltage DC drives. The selection should be discussed with xxxxx electrical engineering representative to provide standardization when possible. 

SOLID-STATE VARIABLE-SPEED AC MOTOR CONTROLS CONTROL OF DC MOTORS DC Motor Starting and Braking Speed Control DC Drive Characteristics PROTECTION OF MOTOR CONTROLLERS Electrical Enclosure Types and Specifications Motor Overload (Running) Protection Other Types of Motor Protection Short-Circuit Protection Protection of Solid-State Motor Controls COMBINATION STARTERS Interrupting Rating... 

Troubleshooting Solid-State Variable-Speed (AC) Drives MOTOR CONTROL CENTERS Motor Control Center Specifications APPLICABLE CODES AND STANDARDS BIBLIOGRAPHY... 

Motor drive 1. Extruder 2. Take-up capstan 1. Extruder output 2. Line tension 1. Solid state controllers 2. Electronic controllers... 

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