Calculating Joules from Watts for Microwave Capacitor

In summary, a capacitor rated for 2100v can't be used in a microwave that is only rated for 1800 watts.
  • #1
Samson4
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How can a microwave I took apart have a .9 microfarad capacitor rated for 2100v? The microwave is rated at 1800 watts. What am I missing?
1/2 CV*2=1.98 joules
 
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  • #2
The capacitor won't be able to power it for a long time then (can you calculate for how long?), but that was never its purpose.
 
  • #3
Samson4 said:
How can a microwave I took apart have a .9 microfarad capacitor rated for 2100v? The microwave is rated at 1800 watts. What am I missing?
1/2 CV*2=1.98 joules
I don't know why do you calculate capacitor energy. Do you know how a microwave power supply works?
 
  • #4
mfb said:
The capacitor won't be able to power it for a long time then (can you calculate for how long?), but that was never its purpose.

I don't know the formula for such a calculation. How can it draw more power then the capacitor is able to provide? The power supply isn't charging to higher voltages than it's rated for.
 
  • #5
zoki85 said:
I don't know why do you calculate capacitor energy. Do you know how a microwave power supply works?

I don't understand what you're asking me.

A microwave power supply works by providing a high voltage ac current to a doubler circuit. It then feeds the rectified current into a magnetron. I am definitely not the one to be answer question of the sort though.
 
  • #6
Samson4 said:
I don't know the formula for such a calculation. How can it draw more power then the capacitor is able to provide? The power supply isn't charging to higher voltages than it's rated for.

Total energy stored in a capacitor is not the same thing as the power it is able to provide. I assume the purpose of this capacitor is to help smooth the output DC current/voltage? If so, then it's constantly being charged and discharged. The current and voltage during capacitor discharge should be nearly the same as they are at the peak of the AC signal (unless you have a poor quality filter circuit) so the output power should remain relatively constant with only a small ripple. Having too small of a capacitor for your output would greatly increase the ripple effect.

I'd provide formulas for determining all this, but I don't happen to know them. Looking around on google did net me the following link though. Maybe it can help?
http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=4856&context=ujmm

I think the key point here is that the capacitor is only discharging for a short time before being charged again. If sized correctly, the drop in voltage and current between the start and end of discharge is small, so output DC power is relatively constant and equals the input power (ignoring losses).
 
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  • #7
Samson4 said:
A microwave power supply works by providing a high voltage ac current to a doubler circuit. It then feeds the rectified current into a magnetron. I am definitely not the one to be answer question of the sort though.
Then, if you know how it works, I don't know what is bothering you...
 
  • #8
zoki85 said:
Then, if you know how it works, I don't know what is bothering you...
I thought it was a power capacitor; that is what was bothering me. Drakkith already helped me, but thanks anyway.
 

1. How do I calculate the joules from watts for a microwave capacitor?

To calculate the joules from watts for a microwave capacitor, you can use the formula J = W x t, where J is the energy in joules, W is the power in watts, and t is the time in seconds. First, determine the power rating of your microwave capacitor in watts. Then, calculate the time it takes for your microwave to run by multiplying the cooking time per minute by the number of minutes you plan to cook. Finally, plug these values into the formula to calculate the joules.

2. Can I use the wattage listed on my microwave to calculate joules?

Yes, you can use the wattage listed on your microwave to calculate joules. The wattage listed on a microwave is the power rating, which is measured in watts. You will need this value to calculate the joules using the formula J = W x t.

3. How do I convert watts to joules?

To convert watts to joules, you can use the formula J = W x t, where J is the energy in joules, W is the power in watts, and t is the time in seconds. First, determine the power rating of your microwave capacitor in watts. Then, calculate the time it takes for your microwave to run by multiplying the cooking time per minute by the number of minutes you plan to cook. Finally, plug these values into the formula to calculate the joules.

4. What is the relationship between watts and joules in a microwave capacitor?

Watts and joules are both units of measurement for energy. Watts measure the rate of energy transfer, while joules measure the total amount of energy. In a microwave capacitor, the watts indicate the power rating, while the joules represent the total energy used during the cooking process. They are related by the formula J = W x t, where J is the energy in joules, W is the power in watts, and t is the time in seconds.

5. Why is it important to calculate joules from watts for a microwave capacitor?

Calculating joules from watts for a microwave capacitor is important because it allows you to understand the total energy used during the cooking process. This information can be useful for determining the efficiency of your microwave and managing your energy consumption. It also gives you a better understanding of the power and energy requirements for different cooking tasks, helping you to use your microwave more effectively.

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