Adjustable voltage

One of the oldest adjustable-speed drives is the Ward-Leonard system. This consists of an ac to dc motor-generator set and a shunt or compound-wound dc motor. Speed is adjusted by changing the generator voltage. A functional equivalent of this drive uses an adjustable-voltage rectifier feeding a dc motor. This system has only one rotating machine in contrast to the three of a conventional Ward-Leonard system. 

Typical applications for adjustable-voltage, adjustable-speed dc drives include winders, paper machines and auxiliaries, blending systems, feeders, extruders, calendars, machine tools, range and slasher drives, cranes, hoists, shovels and draghnes, and an almost unhmited variety of drives requiring the flexibility and efficiency possible with direct current. 

For speed ranges of 3 to 1 or greater, adjustable-voltage operation is recommended. The adjustable-voltage drive usually includes a motor-generator set to supply an adjustable voltage supply to the armature of the drive motor. With this method of operation, a speed range of 10 to 1 readily obtained. 

With an adjustable voltage supply to the armature, at speeds below basic, the motor is suitable for a constant-torque drive. Minimum speeds are limited by temperature rise, because the motor carries full-load current at the lower speeds and at low speeds... 

When designing a PCB for a switcher IC, try to plan ahead and leave the option of moving back from a fixed-voltage part to an adjustable-voltage part (leave room for two resistors). That is a likely retreat in the face of various problems you may encounter. 

Summary. We suggest a simple system of two electron droplets which should display two-channel Kondo behavior at experimentally-accessible temperatures. Stabilization of the two-channel Kondo fixed point requires fine control of the electrochemical potential in each droplet, which can be achieved by adjusting voltages on nearby gate electrodes. We study the conditions for obtaining this type of two-channel Kondo behavior, discuss the experimentally-observable consequences, and explore the generalization to the multi-channel Kondo case.1... 

Rotating electrical machines shall be tested at standstill and running with 0.9X 1.0X their rated speed. The rotor causes a certain turbulence of the test gas, resulting mainly in a considerably increased dp/dt value [2] and enhanced peak pressure. Cage induction motors may be fed from outside with an adjustable voltage and frequency via a frequency convertor, motors with sliprings or commutators need an auxiliary drive, e.g. a small cage induction motor powered by said frequency convertor. 

If this cell is now connected to an adjustable voltage (e.g., a battery), the potential E can be changed at will and the reaction system, O R, driven in the forward or reverse direction. Let us assume that the potential at E is made more positive, so that the net reaction at the electrode is the reduction of O to R. Eventually there will be reached a new equilibrium state in which the ratio (0)/(R) will be smaller as indicated by Eq. (XVII.8.4) "... 

A high voltage power supply is attached to the spray gun in a corona charging system. These power supplies provide an adjustable voltage (typically... 

The (27) relays should have an adjustable voltage range to cover for the 80% voltage condition, typically 50% to 100%. The relay should have a time delay that is adjustable up to at least 0.5 second. 

This operation is useful, for example, in the removal of offsets where through the use of a variable resistor, an adjustable voltage level can be subtracted from the other inputs. We will see a specific example of the use of this op-amp circuit later in this chapter for a piezoelectric force-transducer application. 

Figure 10.29 shows a standard configuration for a positive or negative, three-terminal, adjustable voltage regulator. 

The electronic workshop requires little, basic, very common and cheap instmmentation. Main elements are soldering iron, multimeter, oscilloscope, adjustable voltage supply, and function generator. 

Experimental results are also frequently evaluated by a pocket calculator or a computer, for example, the electrical resistance of a wire may be derived by dividing the adjusted voltage by the measured current. As a general rough rule as to how to present experimental results we may state that the last but one digit should be really accurate and be secured by the experimental method used. In other words, you are not accountable for the last but for the last but one digit. 

Shunt-Wound Motors. Shunt-wound and stabilized shunt-wound dc motors can supply both constant speed at any control setting and a wide speed range that is field-controllable (Fig. 5.118). Most shunt motors are operated from adjustable voltage power supplies and, therefore, do not need auxiliary starting provisions. 

The addition of p i), P2 t) and Pm(0 by means of a potential recorder gives the course of the total power p t). The curve p(t) with relation to the constant baseline po imparts q (Fig. 2.2). If po is compensated by an adjustable voltage source, only the desired q is recorded. 

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