Other Parts Discussed in Thread: DRV8874
we have did the spice simulation for DRV8256 using (DRV8874 model) please find the noise generated in the circuit, request to confirm if we can proceed or need to take any precaution in new design.
Rad/s = RPM * 6.283185307 / 60
DC motor spice model properties
Table DC Motor Properties |
||
|
Property.. |
Meaning.. |
Measured in.. |
|
R |
Series winding resistance |
ohms |
|
L |
Series inductance |
Henries |
|
BACK_EMF |
Back electromagnetic field constant |
volt-sec/rad |
|
K_TORQ |
Torque constant |
N-m/amp |
|
K_VISC |
Viscous frictional coefficient |
N-m-sec/rad |
|
INERTIA |
Rotor moment of inertia |
N-m-sec2/rad |
|
CONST_FRIC |
Constant friction torque |
N-m |
- Vbackemf= BACK_EMF X(Motor speed)
- When the 100w motor is under the maximum load condition, CONST_FRIC =45kg-cm=45* 0.09807=4.41N-m, Vip=24V, I=5.5A, winding resistance = 1.8R, winding inductance = 0.78mh
Motor speed = 130rpm=130*6.283185307 / 60 = 13.61rad/s
Vbackemf = Vip-R*i= 24-1.8*5.5=14.1V
BACK_EMF = Vbackemf / (Motor speed) = 14.1/13.61 = 1.036 V/rads
K_TORQ = CONST_FRIC /I = 4.41/5.5=0.8 N-m/A
K_VISC = CONST_FRIC / (Motor speed) = 4.41/13.61 = 0.32 N-m/rads
INERTIA = CONST_FRIC / (Motor speed*60s)=4.41/(13.61*60) = 0.0054 N-m/rads2
Simulation circuit
Simulation wave
The part where noise occurs is because drv8874 does not have a noise model.
- When the 100w motor is under the spike load condition
Since the provided drv8874 spice model does not provide noise characteristics, it is difficult to simulate spike load.
Regards
arun
