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4-5 Large Load Inertia Adjustment and
Dynamic Brake
The applicable load inertia of the Servomotor is the value of the load inertia at which the Servo
Drive circuit is not destroyed in normal usage conditions. Use the Servomotor at or below the
applicable load inertia, and note the cautions below regarding adjustment and dynamic
braking.
Adjustment When the Load Inertia Is Large
In the instances below, realtime autotuning may not function properly. In this event, improve
the load conditions, or perform manual tuning to set the gain and the inertia ratio.
When the load inertia is less than 3 times or over 20 times the rotor inertia, or is over the applicable
load inertia ratio.
When the load inertia varies.
When the load has low mechanical rigidity.
When backlash or non-linear conditions occur in the load.
When the acceleration/deceleration torque is less than the unbalanced load or viscous friction
torque.
When a speed of 100 r/min or higher or an acceleration/deceleration of 2000 r/min per second or
higher continues for no more than 50 ms.
Dynamic Brake When the Load Inertia Is Large
Because the dynamic brake is used for emergency stopping, the rating is for short time intervals.
To prevent wire breakage, smoke, and fire during dynamic braking, pay attention to the following
points.
Do not intentionally start and stop the motor by Servo ON/OFF.
Do not drive the motor using an externally applied power. Do not turn ON the power while the
motor is rotating.
If motor rotation stops due to dynamic braking, establish a stop time of at least 3 minutes until the
Servo is turned ON again.
The dynamic brake converts the rotational energy of the motor into heat by the dynamic brake
resistance.
The rotational energy of the motor is calculated using the equation below.
Rotational energy of motor
J
: Load inertia + rotor inertia of motor
N
: Motor speed
When the load inertia is large or the rotation speed is high, the load on the dynamic brake
circuit increases. Set the maximum operating rotation speed appropriately for the load inertia.
You can specify in the parameters whether or not the dynamic brake operates in the conditions
below.
A 5 kW or less Servo Drive enters the dynamic braking state when the control power turns
OFF, regardless of the settings.
OMNUC G5-Series AC Servo Drives Users Manual (Built-in MECHATROLINK-II communications type)
4-5 Large Load Inertia Adjustment and Dynamic Brake
1
=
J
ω
2
2
1
N
J
(2
)
2
(
)
2
2
60
[W]
[r/min]
4
4-54
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