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            Electric potential, torque and energy equation

            Electric potential, torque and energy equation 
            Electric potential, torque and energy equation (1)  Electric potential (Figure 6)
            From V=E+2△U+I*r we get E=V-2△U-I*r
            Meanwhile E=KE*Φ*n(armature back EMF)
            V: power supply voltage (Unit: V)
            2△U: brush voltage drop (Unit: V)
            I: armature current (Unit: A)
            R: rotor resistance (Unit: Ω)
            KE: EMF constant = Z/60 (for a 2-pole motor.
            Z: number of conductors)
            Φ: magnetic flux (Unit: Weber) = average magnetic flux density B * width of magnetic pole *effective length of rotor 
            N: speed (Unit: rpm)
            (2)  Torque
            TE=KTΦ*I(electromagnetic torque: N.M)               ?KT: torque constant = Z/2π
            Φ: magnetic flux (unit: Weber)                                  I: armature current (unit: A)
            (3)  Relationship between power and torque?br>P=T*n/97500        P: power(unit: W)      ?T: torque (unit: g.cm)        n: speed (unit: rpm)
            When the unit of T is “N?m? P=T*n/9.55(unit: W?br>(4)  Energy equation(Figure 7):
            Electric potential, torque and energy equation P1=2△U*I+I2r+PE
            PE=P2+PFe+Pmec
            PE: electromagnetic power   P2: output power
            Pmec: mechanical loss      PFe: iron loss
            P2=P1-2△U*I-I2r-PFe-Pmec (unit: W)
            Efficiency: η=P2/P1*100%
            PFe+Pmec is also called no load power
            P0=PFe+Pmec
            PE=P2+P0 and TE=T2+T0


            (5)  Energy transmission graph: (Figure 8)
            Electric potential, torque and energy equation


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