7.2 Specifications and Ratings
7.2.7 Load Moment of Inertia
7-8
7.2.7
Load Moment of Inertia
The load moment of inertia indicates the inertia of the load. The larger the load moment of iner-
tia, the worse the response. If the moment of inertia is too large, operation will become unsta-
ble.
The allowable size of the load moment of inertia (
J
L
) for the Servomotor is restricted. Refer to
on page 7-4. This value is provided strictly
as a guideline and results depend on Servomotor driving conditions.
An Overvoltage Alarm (A.400) is likely to occur during deceleration if the load moment of inertia
exceeds the allowable load moment of inertia. SERVOPACKs with a built-in regenerative resis-
tor may generate a Regenerative Overload Alarm (A.320). Perform one of the following steps if
this occurs.
•
Reduce the torque limit.
•
Reduce the deceleration rate.
•
Reduce the maximum motor speed.
•
Install an External Regenerative Resistor if the alarm cannot be cleared using the above
steps.
7.2.8
Servomotor Heat Dissipation Conditions
The Servomotor ratings are the continuous allowable values when a heat sink is installed on the
Servomotor. If the Servomotor is mounted on a small device component, the Servomotor tem-
perature may rise considerably because the surface for heat dissipation becomes smaller.
Refer to the following graphs for the relation between the heat sink size and derating rate.
When using Servomotors with derating
, change the overload warning and overload alarm detec-
tion timing in advance based on the overload detection level of the motor. Refer to the following
section for the overload detection level of the motor.
7.2.6 Servomotor Overload Protection Characteristics
Note: The derating rates are applicable only when the average motor speed is less than or equal to the rated motor
speed. If the average motor speed exceeds the rated motor speed, consult with your Yaskawa representa-
tive.
The actual temperature rise depends on how the heat sink (i.e., the Servomotor mounting sec-
tion) is attached to the installation surface, what material is used for the Servomotor mounting
section, and the motor speed. Always check the Servomotor temperature with the actual equip-
ment.
Important
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Derating rate (%)
Heat sink size (mm)
Heat sink size (mm)
Derating rate (%)
SGM7G-03 and -05
SGM7G-09, -13, and -20
SGM7G-30, -44, and -55
SGM7G-75
SGM7G-1A and -1E
Derating rate (%)
Heat sink size (mm)
Heat sink size (mm)
Derating rate (%)
