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Capacitors on motors?

Old 06-23-2003, 10:25 PM
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Default Capacitors on motors?

Hi, my Greatplanes speed 280 motor came with two capacitors on it. Two on each lead. I was wondering what these were for and if they are neccesary, I was thinking they were so the radio doesn't interfere with it or something like that... I have another motor I would like to use that doesn't have capacitors. Would I need to solder some on to be able to use it? thanks!
Old 06-24-2003, 02:17 PM
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Default Capacitors on motors?

Cap's on a DC brushed motor stops or help stop RFI (Radio Frequency interface) EMI ( Electrical Magnet Interface) Long time
ago we had just plain copper wire for spark plugs on cars and
changed to carbon wires to help RFI for many thing includeing TV
jumping around. Their are needed even to help your own radio
reciver in the airplane. CU
Old 06-24-2003, 06:14 PM
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Default Capacitors on motors?

Ok, now I know that they are needed, what kind of capacitors would I need? I see on the Radio Shack website lots of different kinds of capacitors with all these different numbers and such. The number 103 is on the capacitors on my motor. How many pF would there need to be and V? Thanks again... I just want to make sure I put the right ones on there.
Old 06-25-2003, 02:19 PM
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Default Capacitors on motors?

103 is .01 uf witch is micro farad 3ea . one + to - then another
+ to case of motor then - to case of motor. RFI is very hard
FCC has many engineer's working in this area and still a lot questions. CU
Old 07-03-2003, 07:17 PM
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Default Capacitors on motors?

e-bird, why do we need to go to the case of the motor? I always wondered.
John
Old 07-03-2003, 07:32 PM
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Default Capacitors on motors?

Steel does contain the RFI so they try to keep everything within
the motor can same a magnet flux lines they try.CU
Old 07-04-2003, 01:04 PM
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Default Capacitors on motors?

It is important the the capacitors used be "ceramic" style. The value of the capacitor need not be specific. Most use a .01uf capacitor but other values can be substituted. If you want to know more about the electric motor and use of capacitors/schottsky diodes go to the web site: www.ezonemag.com and click on "FAQ" on the left side. There, you will find lots of info on electric flying and in the electric motor section of the FAQ's you will find an answer to the capacitor question. An additional capacitor can be added between the two terminal leads on the motor. The capacitors are there to reduce the electrical "noise" generated by the arcing of the brushes that can interfere with radio reception. As E-bird said, capacitors are used on automobiles to surpress the spark plug noise that is detected by the car radio. To add to the issue, some ESC manufacturers will include a "Schottsky diode" to protect the ESC from 'back emf' and let the ESC run more efficiently and cooler. Back EMF (electro motive force) is the electricity that comes from the motor when it becomes a generator. If you were to hook up a volt meter to the motor leads (no battery attached) and spin the prop with your finger you will see a voltage that is generated.
Old 07-07-2003, 06:47 PM
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Default Capacitors on motors?

Thanks Tippie and e-bird. I never expected such a complete answer.
John Smith.

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