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The first step in selecting a motor for your application is to come up with any two of the following three parameters: Required Power, Speed, and Torque. Once you know any two of these, you can calculate the third by using the following equation: P (watts)=(Torque (in-oz) x Speed (rpm))/1352. Then comes the available voltage you have. By knowing the available voltage and the required speed, you can determine the Kv value of the motor that will fulfill your application's needs.
***NOTE: by selecting the Kv of the motor, the sizing process has just begun. The most important factor in selecting which motor will work in your application is to make certain that the amount of heat that is generated in the motor can be safely dissipated.
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Required
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1810 rpm
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This application requires that the selected motor have Kv = 1810 rpm/12V
With this value in mind, you can search our standard product list and select a motor which has a Kv close to the one you have calculated. If one can not be found we can build a motor with a custom number of turns to specifically meet your needs.
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11.20 in-oz
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15.00 watts
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Available
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12.00 v
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Motor Specifications
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1817/8
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As we have calculated, this motor can safely dissipate 33.08 watts of heat. You now have to calculate the losses in the motor and see if they are less than or equal to the amount the motor can safely dissipate.
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167 rpm/V
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8.1 in-oz/A
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14.00 watts
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0.26 ohm
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3 in
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1.8 in
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Total Surface Area (TSA) =
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22.05 in^2
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Heat Dissipation Capability =
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1.5 x TSA
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33.08 watts
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Losses
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Power Loss at Speed (No Load)
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In very simplified terms, a DC brushless motor's losse can be broken down into two major categories:
1) losses due to hysterisis and drag torque (V x Io)
2) losses due to the resistance in the motor's windings (I2 x R)
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Io x V
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4.8 watts
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Torque Loss at Speed (No Load)
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P1 x 1352/S
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3.59 in-oz
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Power Loss due to Current
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I2 x R watts
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.87
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The losses in the motor are only 5.67 watts which are less than the 33.08 watts the motor can safely dissipate. You can now select this motor or try to find a smaller, lighter one.
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P1 + P2
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5.67 watts
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Requiremtents After Losses
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As you can see, this motor only requires 11.31 volts to provide the required speed and 1.83 amps to provide the required torque.
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P + P3
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20.67 watts
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T + T1
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14.79 in-oz
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Ttot/Kt
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1.83 A
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IR + S*1/Kv
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11.31 v
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P/Ptot
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73%
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*** NOTE: The above calculations are merely for demonstration purposes.
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