# Looking for 22K, 3W, 2512 SMT with >=500V(working) rating

Good Day,
I am a design engineer and have an application where I need a 3W, 2512 SMT Power resistor 22K, 5% (nominal) that has a working voltage >= 500V. I see many that have a 500V overload but only 250V working.
Please let me know if you can suggest anything.
Thank you.
JNiland

Welcome to the Tech Forum.

What you are asking for is not possible. A 3 Watt 22K Ohm resistor cannot handle 500V continuously, as it would exceed it’s power rating. According to Ohm’s law, if one applied 500V to a 22K Ohm resistor, a 22.73mA current would flow . . .

`500V / 22,000 Ohms = 0.02273A`

. . . and this would mean it would be dissipating 11.36 Watts – nearly 4x its rated value.

`500V x 0.02273A = 11.36W`

The reason for the voltage rating is to satisfy our internal voltage derating requirements. The actual application is for a Half-Wave rectified 240VAC (with high-line considerations) PEAK voltage derated to 80% of working voltage—gives a voltage rating of 466V. That’s the reason.

Ah, I see.

This is a bit larger, but have you taken a look at the SMF322KJT?

The datasheet does not specify a “Max. Overload Voltage” but it does state that its “Max Operating Voltage” is 500V.

Thank you, yes, I have seen that one but was trying to keep my PC artwork in-tact as much as possible.

Because the current is 1/2 wave rectified, it turns out that I can just get away with a 2W and still have a safety factor. The CRGP2512F22K from TE will work, but our company requires a second source if at all possible. Do you have any insight into that?

Thank you,

Hi jnilandhayward,

No, sorry. The best alternative I could find in the 2512 size and rated 2W or more was the CRM2512-JW-223ELF, which is rated for 300V max working voltage and 600V max overload voltage.

Ok, thank you.