I'm trying to make a swing rotor centrifuge and find a proper BLDC motor to reach 6000G with capacity of 4x50 ml Falcon tubes. I did the calculations roughly but I'm not so sure about them and also couldn't find a proper motor for my calculations.
My rotor will be something like this;
Well for my calculations;
- Mass of the system : 250 g (50 g for body and 4x50 g for tubes)
- Radius of the body : 6.5 cm (I'm trying to minimise it to minimise the inertia)
- RCF : 6000
- Ramp-up from 0 to 6000G : 10 s
And probably my supply voltage will be 12 V or 15 V and my custom ESC can deliver up to 20 A.
And from those inputs I get;
- Inertia : 0.000528125 kgm2
- Angular Acc. : 95.1056763541775 rad/s2
- RPM : 9100
- Torque (with 20% safety margin) : 60.27 mNm
- Power : 57.4 W
But for example when I go and search for a motor such as 200 W High Power Brushless Outrunner DC Motor Bldc Motor Price
It seems the torque is well within specs. But to get 9100 RPM I need to supply 10.1 V which may cause decrease in torque (?).
Also taking Torque Constant into account I get; 5.7 A and it seems too low to me. I mean can I really make this thing spin from 0 to 9100RPM in just 10 seconds with just 10 V and 5 A?
Additionally, there is also Back EMF which I still didn't quiet understand. For the motor in the link, BEMF constant is 0.0011 V/rpm and when I calculate torque producing voltage I get 0.6 V, does this mean that I actually drive this with 0.6V? If so, than I need 95 A to spin it with 9100 RPM? But with terminal resistance involved, my available current is 0.6/0.1 = 6 A, so I can't drive this with 95 A, because of terminal resistance?
As you can see, I'm really confused and I'm really new at this things, so any help would be great.