What is the resistor safety factor?
But for use in a hazardous area, safety factor is taken as 1.5 while selecting resistor wattage. Hence, wattage rating with safety factor of the resistor = wattage rating (W2) × safety factor = 132.3 mW × 1.5 = 198.45 mW. Therefore, W2 × 1.5 < 0.25 W. Thus, the wattage rating is within the safe limit.
What is power rating in resistor?
The power rating of a resistor indicates how much power a resistor can handle before it becomes too hot and burns up. Power is measured in units called watts. The more watts a resistor can handle, the larger and more expensive the resistor is.
What is the specification given to a resistor to determine the maximum power?
The power rating of a resistor is the specification given with a resistor that serves to tell the maximum amount of power that the resistor can withstand. Thus, if a resistor has a power rating of ¼ Watts, ¼ Watts is the maximum amount of power that should be fed into the resistor.
What physical characteristic determines the power rating of a resistor?
Every resistor has a maximum power rating which is determined by its physical size as generally, the greater its surface area the more power it can dissipate safely into the ambient air or into a heatsink.
How is the rating of a resistor determined?
The rating is always for given conditions, such as the ambient temperature, or when mounted on a heat sink. You determine the power in a resistor by computing the voltage across times the current thru it. Usually a safety factor is also used, so the rating is at least twice the expected power. Such derating helps make reliable circuits.
What should the safety factor be for resistors?
As an ex-Navy electronics technician, I’ll show my predjudice by pointing you to some Navy training materials. Typically, a safety factor of 50% is used in circuit design, when it comes to resistors.
When do you need to derate a resistor?
In a nutshell, designs must not violate resistor power or voltage ratings; these are resistance-dependent parameters. Power ratings must be reconciled with the operating temperature. If the circuit operates at temperatures exceeding the resistor’s rated temperature, resistor power handling must be derated appropriately.
What happens when a resistor is too large?
In the process of absorbing power to discharge excess power, if the inductance value of the resistor is too large, it is easy to generate oscillation, and other components in the circuit, power supply and The device itself inflicts damage and even burns many internal devices directly.