"SURE" BRAND WIRE WOUND RESISTOR - SCF

 

Ceramic Encased Axial Lead with Fusible Rating Wire Wound Resistor

Ceramic Encased Axial Lead With Fusible Rating Wire Wound Resistor, Brand Wire Wound Resistor, Resistor, Thane, India

Introduction:

'SURE' provides fusible resistor which fuse or blow if they are subjected to an abnormal spike of voltage / current. SCF Series is a low cost resistor fusible resistor which provides circuit protection for overload or component failure. The resistor will open quickly under continuous load and prevent circuit board from damage and hazards.

 

 

Features:

 

        High Power dissipation in small volume

        High surface insulation property

        Completely fire proof and welded construction

        Available in PCB type and capacitor type terminals

        Formed leads available on request

        Low inductance type available on request

        Long leads also available

 

 

General Specifications:

 

DESCRIPTION

SCF03

SCF04

SCF06

SCF09

SCF12

SCF20

Resistance range, Series

And tolerance (1)

10 %

5  %

E24 Series

0.01 W - 0.05 W

0.06 W - 100 KW

Maximum dissipation at Tamb = 40 C

03 W

04W

06 W

09 W

12 W

20 W

Maximum permissible voltage

(volts DC or RMS)

V =√ (Pn R)

Insulation voltage

> 2000 V

Temperature coefficient. (2)

R < 10 W: 0 to +600ppm/C

Operating temperature

R ≥  10 W: -100 to +150ppm/C

- 55 C to + 275 C

Stability DR/Rmax after:

Lead, 1000 hours

Climate tests

Short time overload

 

5.0% + 0.1 W

3.0% + 0.05 W

4.0% + 0.05 W

 

(1)   Tolerances, 1% and 3% available on request

(2)   Temperature coefficient, 30, 50 and 90ppm/C, available on request

 

Mechanical Data:

 

 

 

Table 1         

TYPE

L

D

d

SCF03

15 1.5

7.5 0.8

0.81 0.03

SCF04

25 1.5

7.5 0.8

0.81 0.03

SCF06

25 1.5

9.5 0.8

0.81 0.03

SCF09

38 1.5

9.5 0.8

0.81 0.03

SCF12

38 1.5

11.0 0.8

0.81 0.03

SCF20

50 1.5

11.0 0.8

0.81 0.03

Dimensions in mm

 

Construction

SCF: The resistor element is a resistive wire, which is wound, on ceramic rod. Tinned copper leads are connected to the caps by welding. The resistor body is housed in a rectangular ceramic case with a special inorganic potting which is non-flammable, will not melt even at high overloads and is resistant to most commonly used cleaning solvents and moisture.

 

Electrical Characteristics

 

DERATING

 The power that the resistor can dissipate depends on the operating temperature; see below

 

 

Fig - Maximum dissipation (Pmax) in percentage of rated power as a function of the ambient temperature (Tamb)

 

Applications:

 

The SCA Series is recommended for the use where occasional overload is upto 125% for long time [upto 2 Hrs.] are probable. This Series is also preferred for aesthetic value. The fusible resistors (SCF) are also available in this series.

 

 

Test and Requirements

 

Essentially all tests and requirements present in table below follow the schedule of IEC standard publication 60115-1, 60115-4 and 60068.

TEST

PROCEDURE

REQUIREMENTS

Insulation resistance

500 V (DC); during 1 minute

V-block method

Rins min 100 MW

Voltage proof on

insulation

 

1000 V (RMS); during

1 minute V-block method.

No breakdown or flashover

Temperature

Coefficient

Between

-55 C at +275 C:

R < 10 W

R ≥10W

0 to +600ppm/C

+ 150 to - 100ppm/C

Short time overload

5 times the rated wattage for 5 sec

DR/Rmax: 2% +0.05W

Robustness of terminations:

 

Tensile all samples

 

 

Bending half number of samples

 

Torsion other half

Number of samples

 

 

 

Load 10N; 10 s

 

 

Load 5N; 4 90

 

 

3360 in opposite

Directions

No visible damage

DR/Rmax; 2% + 0.05W

Solderability

(after ageing)

16h at 155 C, leads

Immersed in flux 600, leads immersed 2 mm for 2 0.5 s in a solder bath a 235 5 C

Good tinning;

No damage

DR/Rmax; 0.5% 0.05W

Resistance to Soldering heat

Thermal shock; 3s, 350 C;

6mm from body

DR/Rmax; 4% + 0.05W

Rapid change of

temperature

30 minutes at 55 C and 30 minutes at + 275 C;

5 cycles

No visual damage

DR/Rmax; 5% +0.05W

Climate sequence:

 

Dry heat

 

Damp heat

(accelerated)

1st cycle

 

Cold

 

Damp heat (accel) remaining cycles

 

 

16h, 275 C

 

24h; 25 C to 55 C;

90% to 98% R.H.

 

 

2h; - 65 C

 

6 days; 55 C;

90% to 98% R.H;

DR/Rmax; 3%+ 0.05W

Damp heat

(steady state)

56 days; 40 C;

90 to 95% RH

Loaded with 0.01 Pn

DR/Rmax; 5% +0.05

Endurance

40 C

1000 hours load with Pn or Vmax 1.5h ON 0.5h OFF

No damage

DR/Rmax  5% +0.1W

 

NOTE :  Fusible resistors are not standard resistor types and each type of fusible resistor must be designed to suit a particular application.

 

Data required to design a fusible resistor are:

  1. The type you require -
     Ceramic Encased or Axial Lead Type

  2. Resistance in ohms.

  3. Power rating in terms of watts.

  4. Tolerance.

  5. Fusing current - The current at which the resistor must fuse or blow.

  6. Fusing time - The duration within which the resistor must fuse or blow, on being subjected to the fusing current.

At SURE if no special data is provided, a fusible resistor can be made as per the following chart :

FUSING CHARACTERISTICS :

 

POWER

FUSING TIME

MAX

16 X Wattage

1 min

20 X Wattage

40 sec

24 X Wattage

30 sec

28 X Wattage

20 sec

32 X Wattage

15 sec


 

TYPICAL APPLICATIONS :

 

As mentioned previously a fusible resistor is a dual purpose component -
  (a)   In normal conditions it functions as a resistor.
  (b)   In high overload conditions it acts as a fuse/safety device.
 

In some countries all types of ceramic encased type resistors are wrongly called as fusible resistors. It must be clearly understood that fusible resistors are special purpose, specially designed resistors and are produced mainly in two configurations -

  (a)   Ceramic encased type (SCF) and
  (b)   Flame retardant silicone coated axial lead type. (SSF)

 

 

 

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