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1.Silicone Coating vs Vitreous Enamel Coating:

The traditional method of enamelling Resistors has been superceded by Silicone Resin based coatings over the years. However, there are some applications where the distinct difference that exist between the two gives an edge to enameled type and the designer is advised to select the appropriate coating for their requirements.

We at PEC have pioneered silicone coatings in India and subsequently pioneered the High Quality Vitreous Coatings (different from the available low melting types mostly used in India) to meet the specific demands from customers. A chart showing the important differences is given here.

Parameters
Silicone
Vitreous
Overload capability
Limited
High
Emission of fumes
Yes, but possible to reduce
No
Moisture absorption

Varies depending on coating and processing used

Good vitreous coatings are generally moisture proof

TCR achievable

Low TCRs to 10ppm can be achieved

 TCRs as low as 50ppm can be achieved.
Close tolerances
Yes. Upto 0.05%
Limited to about 0.5%

Deterioration of coating over life

Higher possibility in long tubular type resistors
very limited deterioration, suitable for traction applications

Power handling capability

Normal
Higher as compared to silicone for a given size.
Flammability

Flame proof coatings are available

Flame proof
Cost
Lower cost
Higher cost


2. Surge withstanding capability and high voltage withstanding capability .

Circuit designers often encounters repetitive surges, or low duty cycle pulses, in applications like capacitor banks, motor control and lightning protection. The design of a resistor suitable for each application can vary and be specific to the conditions of the specific circuit or appliance.

PEC has developed the expertise in designing Pulse rated Resistors specific to such applications and also has built up the capability to test such ideas to prove the design.

As no two applications are similar and often the overall size is a constraint, designers are requested to contact PEC R&D engineers for specific solutions.


3. Noise Suppression Resistors

As a natural extension of PEC's high voltage resistor design capability, PEC undertakes the production and testing of typical NSR's for OEM'S. Critical selection of materials and process enables the customer to get custom built NSR devices.


4. Resistor assemblies:

A variety of fused Resistor assemblies with predictable fusing current and time are offered by PEC to customers who need reliable devices of this type.


5. High Precision, Close tolerance Resistors:-

A variety of test instruments rely on stable, low TCR, High accuracy Resistive devices for use as reference devices in their circuits. While there are low cost metal film and chip devices which offer the desired characteristics, wirewound resistors are unique in their performance as they could offer very high stability with very low TCR's and the ability to give a long drift free service.


6. Thermal Considerations:

The Wire Wound Resistors are often required to absorb/ dissipate large amounts of power.  Due to this the resistor surface can get very hot, this can affect the performance of other components placed near it.

PEC offers several circuit specific thermal management ideas to customers.

7. Special TCR's:-

It is possible to build Wire Wound Resistors with specific TCR's from very low TCR values like <10ppm to large TCR's like 3000 PPM, 6000 PPM. Different applications demand different TCR capability and PEC can custom build products required by customers.

The PEC R&D team would be happy to study customer requests and suggest suitable solutions.

 



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