Inertia Constant H vs Starting Time Constant T_a
Inertia Constant H vs Starting Time Constant T_a
(OP)
http://www.eng-tips.com/viewthread.cfm?qid=257084
I think Wolf is perfectly right.
The inertia constant H is the ratio between the rotational energy E_rot stored in the turbogenerator and the nominal Power of the generator P_nom.
H = E_rot / P_nom [kWs/kW = s]
It's more or less artificial. You may calculate the value by using moment of inertia J, nominal rotating speed omega w_nom, nominal moment M_nom
H = (1/2*J*w_nom^2)/(M_nom * w_nom) = 1/2*w_nom * J/M_nom
The starting time constant T_a is the time needed to speed up a rotating system with nominal moment for zero to nominal omega.
As M = J*w', w' = M_nom/J
w' applied during a period of T_a will accelerate the turbogenerator to w_nom. T_a * w' = w_nom. So,
T_a = w_nom * J/M_nom
You can see that T_a is twice the time compared to H.
Regards,
Gunnar
In German T_a is called Anlaufzeitkonstante. Is starting time constant the correct expression?
I think Wolf is perfectly right.
The inertia constant H is the ratio between the rotational energy E_rot stored in the turbogenerator and the nominal Power of the generator P_nom.
H = E_rot / P_nom [kWs/kW = s]
It's more or less artificial. You may calculate the value by using moment of inertia J, nominal rotating speed omega w_nom, nominal moment M_nom
H = (1/2*J*w_nom^2)/(M_nom * w_nom) = 1/2*w_nom * J/M_nom
The starting time constant T_a is the time needed to speed up a rotating system with nominal moment for zero to nominal omega.
As M = J*w', w' = M_nom/J
w' applied during a period of T_a will accelerate the turbogenerator to w_nom. T_a * w' = w_nom. So,
T_a = w_nom * J/M_nom
You can see that T_a is twice the time compared to H.
Regards,
Gunnar
In German T_a is called Anlaufzeitkonstante. Is starting time constant the correct expression?






RE: Inertia Constant H vs Starting Time Constant T_a
And yes, Tm = 2H.
Regards.