The system designer may choose from a wide range of standard high voltage resistor products. For most applications a standard device will be adequate but for some more demanding and specialist applications, only a custom high voltage resistor solution will suffice.
Where a custom resistor solution is required its performance is often critical to the performance of the overall system. To ensure the resistor performs to specification over the long term a close working relationship is required between the system designer and resistor manufacturer during the custom resistor design and development process.
The resistor manufacturer will have a detailed understanding of materials, design limits and manufacturing processes. However, only the system designer can understand the system requirements, mechanical and environmental limitations.
It is important the designer delivers all relevant information to the manufacturer and after review, the manufacturer delivers an honest assessment of what can (and cannot) be achieved. Cost implications of various options and timescales should be discussed at an early stage.
High voltage resistors are used in a wide range of applications. Each application has its own set of key requirements. The system designer should consider both steady state and transient conditions including both electrical and environmental conditions.
The resistor manufacturer will be concerned with ensuring the custom resistor device meets the electrical specification and stability (of resistance value) over the long term. They will consider:
- Changes in resistance value with temperature.
- Stability of resistance value over time.
- Power (and surge) handling capability.
They will carefully consider the environmental and electrical transient conditions that may cause performance degradation or (worst case) resistor failure. The selection of materials and manufacturing process will be crucial to success . To ensure all issues are considered the manufacturer will require the following information:
Maximum continuous current
Maximum continuous voltage
Peak voltage / waveshape
Required resistance value
Surge conditions (amplitude and waveform)
Operating temperature range
Max ambient temperature
Available board area.
Resistor mounting method
Termination type and material.
Length of pin.
Expected in service life.
Target component cost.
Armed with this information the manufacturer may proceed with the custom high voltage resistor design and approval phase. In some cases, this may involve manufacturing a set of prototypes for approval before proceeding to manufacture of production parts.