Calculation of Required Braking Resistance
Max. deceleration torque T [N·m]
If the motor rotation direction and
the motor torque direction are
different, the regenerative energy
will be produced.
Max. rotation speed N [r/min]
The energy is proportional to the
square of the speed.
The regenerative energy momentarily
becomes the largest at this point.
Speed
Time
Torque
Resistance of braking resistor : R ≤
60 × V
2
2π
· (
T - 0.2 × Tm)
·
N
V : 200-V class inverter 362.5 [V]
400-V class inverter 725 [V]
T : Maximum braking torque [N
·
m]
Tm : Motor rating torque [N
·
m]
N : Maximum rotation speed [r/min]
Note
Calculate a braking torque according to Inverter Capacity Selection in the Motor Capacity Selection sec-
tion.
Calculation of average regenerative energy
Regenerative energy is produced when the motor rotation and the torque are opposite in direction.
Use the following formula to calculate the regenerative energy for each period in a cycle.
Pi = N×T×t×1.047×10
-1
Pi
: Regenerative energy in Period i [J]
N : Motor rotation speed [r/min]
When the number of rotations changes,
take an average value.
ex. For linear deceleration
(Nmax+Nmin)/2
T : Deceleration torque [N·m]
t : Deceleration time [s]
Time
Period 2
Period 1
Torque
Speed
For horizontal load
For the average regenerative energy, calculate the time average by adding the regenerative energy
for all periods in a cycle and dividing it by the cycle time, as shown below.
Appendices
A-301
M1 Series EtherCAT Type User’s Manual (I670)
A-10 Overview of Inverter Selection
A
A-10-3 Overview of Braking Resistor Selection
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