Wire wound resistor, Physics

MANUFACTURING:

 

The resistance element is used as a wire, made from special alloys, which have small low temperature coefficient and good stability against environmental conditions. Ceramic substrate is used because the mismatch between linear expansion of ceramic substrate and wire wound is minimized and thus stable characteristics could be obtained. The wire is chosen according to   its resistivity. The actual resistance is adjusted during winding. The resistance required is driven from the length of the wire used, gauge and their resistivity. During winding, one end of the wire is welded on a butt cap. Known length of wire is tightly wound around the ceramic substrate and the other end of the wire is soldered to cap on other end. Since wire is susceptible to mechanical strain, they are annealed at high temperatures. Wire wound resistors suffer from high frequency effects due to winding. Also it is difficult to get high ohm values. Thus a back to back or bifilar winding is used. These resistors suffer from mechanical vibrations and shocks. Thus it is necessary to given adequate protections.

(a)          OPEN WOUND: Wire of nickel is wound on a ceramic rod. These rods are grooved or plain. The wire is thus unprotected. The wire used normally thick and thus limits maximum resistance value. Values available are from 25 kilo ohm to 150 kilo ohm. Wattage rating 10 to 60W.

(b)         VITREOUS ENAMELLEDTHESE resistors are coated with vitreous enamel. It enamels excellent protection against moisture penetration.

SPECIFICATIONS:

Range of value                                                         0.1 ohm to 106 ohms

Temperature coefficient                                             5 ppm/0C

Stability                                                                   >0.05%

Tolerance                                                                >0.5%

Working voltage                                                       < 300 V

Working temperature                                                35 to 3750C

Applications: These resistors are suitable for low resistance and low noise applications. Also these are used when high power handling capacity is required in small size. They find immense used in regulated power supplies, MultiMate's, Wheatstone bridge etc. 

Posted Date: 7/9/2012 5:02:13 AM | Location : United States







Related Discussions:- Wire wound resistor, Assignment Help, Ask Question on Wire wound resistor, Get Answer, Expert's Help, Wire wound resistor Discussions

Write discussion on Wire wound resistor
Your posts are moderated
Related Questions
Neuroscience is a scientific study of the nervous system. Usually, neuroscience has been seen considered as a branch of biology. Thus, it is now present an interdisciplinary scien

Q. An iron box of 400 W power is used daily for 30 minutes. If the cost per unit is 75 paise, find the weekly expense on using the iron box. Energy obsessive in 30 minutes

Keplers Second Law After studying a wealth of planetary data for the motion of the planets about the sun, Johannes Kepler reasons three laws of planetary motion. Kepler's secon


what are they and how do you measure them

why rutherford''s atomic model is failure

Radio waves and microwaves: What are microwaves and radio waves? Ans: Microwaves: 1. The wavelength ranges from 10μm to10m 2. Commonly produced by Electromagnetic osc

How many types of illuminators are there? As there are no standards inside the industry, the term "type" is slightly confusing. Regading to power usage, the lamp illuminators c

What evidence is there supporting the Big Bang theory? In short, the universe is increasing. All of the galaxies we have observed that are great distance away are moving away f