Installation manual

Danaher Motion Kollmorgen Appendix D
SERVOSTAR
®
S and SERVOSTAR
®
CD Series 124
Energy Calculations
To determine if a system needs a regeneration resistor, use the following
procedure:
EQUATION 1
Define the term E
M
which is the kinetic energy of the motor/load minus the
system losses.
E
M
= (1.356/2)(J
M
+ J
L
)
ω
M
2
– 3I
2
M (R
M
/2)t
d
– (1.356/
2
)T
F
ω
M
t
d
Joules
Where: J
M
= rotor inertia (lb – ft – sec
2
)
J
L
= load inertia (lb – ft – sec
2
)
ω
M
= motor speed before decel (rad/sec) =
RPM
9.55
I
M
= motor current during deceleration
R
M
= motor resistance (Ù L – L)
t
d
= time to decel (sec)
T
F
= friction torque (lb-ft)
If this energy is less than that which the BUS Module can store, then no regen
resistor is needed. Thus, the condition for which no regen resistor is required is:
EQUATION 2
E
M
< (1/2) C (V
2
M
– V
2
NOM
)
Where: C = BUS Module capacitance (Farads)
V
M
= max BUS voltage (V)
V
NOM
= nominal BUS voltage (V) = V (L-L)
2
Where: all negative E
M
are set equal to zero before summation (sum all non-
negative E
M
). This represents a worst case in which only the motors that are
regenerating (E
MJ
> 0) decelerate while those whose system losses exceed their
regenerative energy (E
MJ
< 0) remain idle. If Equation 2 is not satisfied, then a
regeneration resistor is required.
Regeneration Calculations
The procedure for calculating regeneration requirements is twofold. Both the
regen resistance value and the resistor wattage rating must be determined.