Large motor starting

[swiminelectricity]

I am running SKim.M y question is, what we need to run by SKIM in order to determine if the motor can start properly.
Thank you in advance.

 

[aolalde]

You should know the load inertia (WK^2), the load spee-torque and the motor speed-torque curves.

The torque requirements to accelerate the load will dictate if reduced or full voltages are required.

The accelerating or starting time in seconds will be:

t= WK^2 x (Drpm)/(308 X Tave)

Drpm = speed change
Tave = Average motor torque minus load torque (Lb*Ft)

Note that at reduced voltage the motor torque is reduced with the squared power of the voltage reduction ratio.

 

[swiminelectricity]

Thanks,Aolalde,

 

[jraef]

You should also know the acceptable bus voltage drop on the system, both primary and secondary, along with as complete a study of the power supply as is possible. Transformer / generator sizes, impedances, cable sizes and lengths, existing loads on line at the time of starting etc.

Just a plug for an excellent product...
We use SKM as our primary modeling tool for predicting RV starting success. In nearly all applications where we have run a simulation, it has been dead on correct! On 3 occasions, competitors claimed to be able to do something that we said couldn't be done because the SKM models did not bear out, and that turned out to be true (and costly for the competitors and end users).

The only minor drawback is in modeling solid state soft starting, because it can only model a fixed current acceleration, not a true ramped acceleration. But to be honest, I cannot see how any PC based sofware program could model all the variable dynamics of ramping the voltage or current, so IMHO it is as good as is reasonably possible.

"Venditori de oleum-vipera non vigere excordis populi"

 

[maypot]

Aolade,

What is the DRPM ?


Bob

 

[jraef]

Delta (change) in RPM.