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Flat Wire Wound Resistors
FRW Series
 

Flat Wire Wound Resistors FRW Series Dimensions
Flat Wire Wound Resistors FRW Series

The FRW Series is designed for vertical or horizontal mounting, either singly or in stacks. Non-magnetic mounting brackets extending through the resistor allow easy and economical mounting. They also aid heat distribution along its entire length and serves as conductors to transfer internal heat to the chassis.
Other features of the FRW Series are lightweight construction, combined with exceptional mechanical strength, and the ability to withstand severe vibration.
Designed to fulfill requirements of high wattage dissipation in limited-space applications, the FRW Flat Wire Wound Resistor has a higher power to space ratio than standard tubular wire wounds. For different operating conditions, these compact resistors are available in two coatings, "D Coat" or "C Coat".

COATINGS
PYROSIL D-COAT is a unique combination of silicone resins and refactory oxidation barriers designed particularly for high temperature operation. It is capable of withstanding temperatures corresponding to five times rated load.
TROPICAL C-COAT is a specially developed silicone coat for the worst conditions encountered, such as on shipboard, in tropical countries and humid climates. Power rating in watts shown in the table should not be exceeded.

TOLERANCES
Standard tolerance is 5%,(50 ohm and above) 10% below. Tolerances as low as 1.0% can be supplied. Further details on application.

ADJUSTABLE  RESISTORS
Adjustable  resistors are available within the maximum resistance range for each type, as shown in the chart.

TAPPED RESISTORS
Tapped resistors may be supplied within the limitations of the resistor size used. The use of a tap results in a small reduction in power rating and ohmage available, since winding space is lost.


 Flat Wire Wound Resistors FRW Series Power Rating

STACKING
FRW Series Resistors are designed for assembly in stacks or gangs, as illustrated. When stacked, each resistor, under load, affects the temperature of its adjoining resistors. To limit the temperature rise of the hottest unit to 250 0C, for "D" coat or 1500C, for "C" coat, It is necessary, depending upon the number of resistors in the stack to reduce the power applied to each resistor by the percentage given in table 1.
For more efficient ventilation, FRW Resistors should be mounted in a vertical rather than a horizontal plane. A lower percentage of de-rating is necessary for vertical stacks, as shown in Table 1.
Two spacer sleeves are required for each resistor (more than one) in a stack assembly, as illustrated in the outline drawing. The required number of spaces should be noted when ordering. Specify as "FRW Spacers."

TABLE 1

Flat Wire Wound Resistors FRW Series Stack Rating

TAPPED RESISTORS
Tapped resistors may be supplied, within the limitations of the resistor size used as listed below. The use of taps results in a reduction in total resistance available, due to loss of winding space. When specifying Tapped Resistors, provide wattage per section.

Flat Wire Wound Resistors FRW Series Dimensions

FRW-20

Single section only

FRW-21

Two sections maximum

FRW-22

Three sections maximum

FRW-23

Four sections maximum

FRW-24

Five sections maximum


POWER RATINGS
The power ratings for Pyrosil "D" and Tropical "C" coatings are based on the ability of the resistor to give long service at full rated load, at the nominated ambients. At higher ambients, the resistor should be de-rated in accordance with the de-rating curve shown.
Full rated load for a Pyrosil "D" coated resistor is based on a temperature rise of 250oC from an ambient of 40oC. Full rated load for Tropical "C" coated resistor is based on a temperature rise of 150oC, from an ambient of 40oC.

DERATING
If operating FRW Resistors in an ambient higher than 40oC., it is recommended that they be derated according to the Derating Curve for High Ambient Temperatures.

Flat Wire Wound Resistors FRW Series Average Temperatures Flat Wire Wound Resistors FRW Series Ambient Temperatures

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