[TechAssist] Re: Voltage Rating of Resistors
- From: Bil Green <tv.vcrrepair@xxxxxxxxxxx>
- To: J Silverman <techassist@xxxxxxxxxxxxx>
- Date: Mon, 25 Apr 2005 15:29:40 -0700
I just called KOA and the engineer said that 100% overvoltage with
carbon film resistors is fine, even with pulses occurring once per
second.
Bil
PC 1000
Mammoth Lakes, CA
760-924-1000
M-Pulse 5000 magnetic pulse generator
http://www.heal-me.com.au/m-pulse5000.htm
Monday, April 25, 2005, 11:03:34 AM, you wrote:
JS> With the current at 5 ma, the resistors would see a peak power of 45
JS> milliwatts each. Only the manufacturer could answer your question.
JS> Jerry Silverman
JS> Greentron Inc
JS> 4 Newland Ave
JS> Greenville SC 29609
JS> Fax/Phone 864 232 3889
JS> mail to: greentron@xxxxxxx
JS> ----- Original Message -----
JS> From: "Bil Green" <tv.vcrrepair@xxxxxxxxxxx>
JS> To: "Jerome Silverman" <techassist@xxxxxxxxxxxxx>
JS> Sent: Monday, April 25, 2005 7:08 AM
JS> Subject: [TechAssist] Re: Voltage Rating of Resistors
>> I don't know the peak power rating of the resistors, but the 900V
>> inverter I am using is current limited to 5mA (the final output,
>> after the voltage doubler is 1700V, at around 2.5mA).
>>
>> Therefor the max power that the 3 resistors (in series) will be
>> subjected to is around 4W total, not 535W. And this would be for
>> less than 0.5 seconds.
>>
>> I just need to know if continually applying an overload voltage
>> to a carbon film resistor (for a fraction of one second, at a
>> pulse rate of 1Hz) will weaken it. They are designed for 100%
>> overvoltage during an overload.
>>
>> Bil
>>
>> PC 1000
>> Mammoth Lakes, CA
>> 760-924-1000
>> M-Pulse 5000 magnetic pulse generator
>> http://www.heal-me.com.au/m-pulse5000.htm
>>
>>
>> Sunday, April 24, 2005, 8:16:33 PM, you wrote:
>>
>> JS> What is the peak power rating of the resistors? You are asking the
JS> three
>> JS> reistors to handle a peak power of 535 watts.
>> JS> Jerry Silverman
>> JS> Greentron Inc
>> JS> 4 Newland Ave Greenville SC 29609
>> JS> Fax/Phone 864 232 3889
>> JS> greentron@xxxxxxx
>>
>> JS> ----- Original Message -----
>> JS> From: "Bil Green" <tv.vcrrepair@xxxxxxxxxxx>
>> JS> To: ".TECHASSIST @ freelists . org" <techassist@xxxxxxxxxxxxx>
>> JS> Sent: Sunday, April 24, 2005 8:22 AM
>> JS> Subject: [TechAssist] Voltage Rating of Resistors
>>
>>
>> >> If anyone is very familiar with the voltage ratings of carbon
>> >> film resistors, I could use some help.
>> >>
>> >>
>> >> I would like to know if the Max. Overload Voltage of carbon
>> >> film resistors (this is 2 x times the working voltage) would
>> >> apply in this instance:
>> >>
>> >> I would like to use three 1.8k, 1/2W resistors* in series
>> >> with a 1700VDC supply to charge a 0.5uF capacitor. It will
>> >> fully charge in approx. one second.
>> >>
>> >> * 1/2W carbon film resistors are rated at 350V (working voltage)
>> >>
>> >> I realize that this is not exactly a surge condition, however
>> >> the voltage exceeding the rating of these resistors would
>> >> only exist for about 1/2 second (and would be below the Max.
>> >> Overload Voltage of the 3 resistors wired in series).
>> >>
>> >> This is to be used in a magnetic pulse generator in which the
>> >> capacitor discharges into a coil once per second (one second
>> >> to fully charge and a very small fraction of one second to
>> >> discharge).
>> >>
>> >> This instrument would only be used for a few minutes per day,
>> >> and must be reliable.
>> >>
>> >> I will be ordering some 1W resistors (500V rating), but have
>> >> a couple units that need to be shipped out on Monday.
>> >>
>> >> From what I've read, it's common for engineers to not consider
>> >> the voltage rating of resistors when designing circuits, so I
>> >> don't feel negligent, since I am doing the best I can at this
>> >> time.
>> >>
>> >> Bil
>> >>
>> >> PC 1000
>> >> Mammoth Lakes, CA
>> >> 760-924-1000
>> >> M-Pulse 5000 magnetic pulse generator
>> >> http://www.heal-me.com.au/m-pulse5000.htm
>> >>
>>
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