Resistor overcurrent problem

tangwei8802429

Resistor overcurrent problem [Copy link]

2 1K2 + 3 22R, all 10W wire wound resistors, are connected to the load circuit together. The peak voltage of the pulse (1us) across the resistor is 400V. Shouldn't the instantaneous current be 54A? According to the resistor data, the maximum instantaneous power is 10 times the rated power, but the current is not that large? How is the maximum instantaneous current of this resistor calculated? If I want to use it for current limiting, how should I deal with this problem?

gmchen

Note that in the data, the short-time overload time is 5 seconds, and your pulse is only 1 microsecond!

maychang

The manual states that the power allowed is 10 times within 5 seconds, which is 3.16 times the current.

Now your overload time is only 1us, the power that the resistor can withstand is much greater than 10 times. How much, you can only ask the manufacturer, or determine it through experiments.

tangwei8802429

maychang posted on 2024-3-12 15:35 The manual says that the power can be 10 times within 5 seconds, which is 3.16 times the current. Now your overload time is only 1us, and the power that this resistor can withstand is much higher than 10 ...

Mmm Good.

maychang

tangwei8802429 posted on 2024-3-12 15:37 Yes, OK.

The ability of various resistors to withstand pulses is different. Metal film resistors have poorer ability to withstand impacts, while wirewound resistors have the strongest ability to withstand pulses.

tagetage

For wirewound resistor pulses (1us), you also need to consider the inductive reactance.

qwqwqw2088

When the pulse duration is less than 5s, the wirewound resistor can withstand an instantaneous power of 5 to 10 times the nominal power.

lanhua

2 1K2 + 3 22R are all 10W wirewound resistors and connected to the load circuit together. The pulse (1us) peak voltage of 400V is measured across the resistors:

There is another parameter, what is the frequency?

qwqwqw2088

Measure the pulse (1us) peak voltage of 400V across the resistor

The magnitude of the instantaneous current is closely related to time, and the instantaneous current does not exist continuously. Whether
the maximum instantaneous power is a single pulse or a continuous pulse is a frequency that needs to be considered.