Resistor design

Make the total resistanee about lOOK or two 47Kohm, 1/2W resistors. Designing the voltage multiplier input eireuit... 

There are two geometries for a ballast resistor, a thin film under the CNT (vertical resistor), or a thin film at the side of the CNT (horizontal resistor). Now, the local field for field emission from carbon is extremely high, 109 V/m, which may be 10 times larger than the breakdown field of many insulators. Given the dimensions of an emission system, it is likely that the thickness of any ballast resistor thin film will be smaller than that of the net cathode-anode distance. Thus, the applied field is likely to cause breakdown in any vertical ballast resistor design. Thus, horizontal ballast resistors are a safer option. However, they are more difficult to implement because they must be placed between each emitter and the current feed. 

ARMATURE REGULATING RESISTORS - Are resistors, designed to regulate the speed or torque of a loaded motor, by placing a resistance in the armature or power circuit. 

Dropping resistor A resistor designed to carry current that will make a required voltage available. 

Lumped-element design, in general, is little supported by convenhonal computer aided design (CAD) systems. Passive integration is usually limited to resistor design. Reasons for this are that the high-frequency-component... 

Thermistors. Thick-fihn thermistors are generally used for temperature compensation in various electronic circuits. They are a special class of thick-film resistors, designed to... 

D. Bender and R. Lathroy, Novel High Performance Resistor Design for Telecommunications A-C Surge Protection, Proc. ISHMAdv. Mail. Tech. Conf., Orlando, 1989. 

Chrome—nickel alloy heating elements that commonly ate used in low temperature furnaces are not suitable above the very low end of the range. Elements commonly used as resistors are either silicon carbide, carbon, or high temperature metals, eg, molybdenum and tungsten. The latter impose stringent limitations on the atmosphere that must be maintained around the heating elements to prevent rapid element failure (3), or the furnace should be designed to allow easy, periodic replacement. 

Amine Cross-Linking. Two commercially important, high performance elastomers which are not normally sulfur-cured are the fluoroelastomers (FKM) and the polyacrylates (ACM). Polyacrylates typically contain a small percent of a reactive monomer designed to react with amine curatives such as hexamethylene-diamine carbamate (Diak 1). Because the type and level of reactive monomer varies with ACM type, it is important to match the curative type to the particular ACM ia questioa. Sulfur and sulfur-beating materials can be used as cure retarders they also serve as age resistors (22). Fluoroelastomer cure systems typically utilize amines as the primary cross-linking agent and metal oxides as acid acceptors. 

In addition to secondarv resistance control, other devices such as reactors and thyristors (solid-state controllable rectifiers) are used to control wound-rotor motors. Fixed secondary reactors combined with resistors can provide veiy constant accelerating torque with a minimum number of accelerating steps. The change in slip frequency with speed continually changes the effective reac tance and hence the value of resistance associated with the reactor. The secondaiy reactors, resistors, and contacts can be varied in design to provide the proper accelerating speed-torque curve for the protection of belt conveyors and similar loads. 

Thyristors have been replacing saturable reactors they are small, efficient, and easily controlled by a wide variety of control systems. A modern crane control drive uses fixed secondary resistors and two sets of primaiy thyristors (one set for hoist, one for lower). With tachometer feedback for speed sensing, the control for the motor provides speed regulation and torque hmiting in both directions, all with static-devices. A wide variety of control systems is possible the control should be designed for the specific application. 

To increase the impedance of the network, a series resistor or reactor is sometimes used to contain the fault level of a system within a desirable limit. This may be required to make the selection of the interrupting device easy, and from the available range, without an extra cost for a new design as well as an economical selection of the interconnecting conductors and cables. Such a situation may arise on HV >66 kV or EFIV > 132. kV transmission networks, when they are being fed by two or more power sources, which may raise the fault level of the system to an unacceptable level. The cost of the interrupting device for such a fault level may become disproportionately high, and sometimes even pose a problem in availability. 

The design philosophy behind the fixed-base drive circuit is to draw current from a relatively low voltage source (3 to 5 V) which is usually provided by an auxiliary winding on the power transformer. The resistor directly in series with the base (R2 as shown in Figure 3-33) should be on the order of 100ohms. Its... 

Continuing the design example, let us use the elosest f pereent resistor value -2.49 K. This makes the aetual sense eurrent... 

Onee again, the designer ean ehoose whether to make the supply operate in the hieeup mode restarting or to have the eontrol and driver seetion eontinue to operate during a short-eireuit eondition. Choosing the value of the eolleetor resistor for 0.5 or 15 mA eurrent seleets the respeetive operation. 

Another faetor is the rated breakdown voltage of resistors. For a one-quarter watt resistor, the rated breakdown voltage is 250 VDC. The one-half watt resistor is 350 VDC. To design safely, two resistors in series should be used on all branehes that are eonneeted to the input line in off-line eonverters. 

I am designating the maximum voltage at the input to the error amplifier to be -1-4.5 V. The MOC8102 has a nominal C r of 100 percent and the TL431 requires a minimum of 1 mA passing through it to operate. This makes the value of the resistor Rl ... 

Then find the value of the feedback capacitor C. The designer knows the value of the input resistor (R). It is the upper resistor in the voltage divider responsible for the voltage feedback to the error amplifier. One then performs Equation B.15. 

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. 

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