37
Rev. 2.0
07/27/2023
MBDV Hardware Manual
4) Analyze
When P
AV
< 0, that is, the total power generated during the deceleration process is less than the
power absorbed by the bus capacitor in the driver, so no external absorption resistor is required.
When P
AV
> 0, that is, the total power generated during the deceleration process is greater than the
power absorbed by the bus capacitor in the driver, and an external absorption resistor is required
to reasonably control the temperature rise of the external absorption resistor. The minimum value
of the resistance power is P
AV
/ 0.5.
◆
Calculation example: 400W SM0602G*L**** is selected, the load inertia is 15 times the motor
inertia, assuming t
dec
(deceleration time + interval time between two decelerations) is 0.5s, and
each movement is decelerated from 3000rpm to 0rpm, then the required power of the absorption
resistor is calculated as:
Since the power absorbed by the bus capacitor in the driver is less than the total power generated
during the deceleration process, an external absorption resistor is required.
B. The external load torque drives the motor, and the motor continuously outputs negative
power.
Most motors are doing positive work, that is, the torque output direction of the motor is consistent
with the rotation direction. In some special applications, the torque output direction of the motor
is opposite to the rotation speed direction, and the external energy will be fed back to the drive.
such as during the downward, vertical movement of a large load. in order to meet the position
requirements and speed requirements of the servo system, the motor will output the opposite force
to overcome the gravity of the external load. When running in this manner for a long time, the bus
capacitor will become saturated and will fail to continue absorbing regenerative energy. At this time,
the regenerative resistor needs to absorb the energy. The power calculation formula is as follows:
T
M
: Motor output torque. Unit: Nm
N
M
Motor speed. Unit: rps
◆
Calculation example:
The torque output direction of the motor is opposite to the rotation speed direction. When the motor
output torque is 0.6Nm and the speed is 2400rpm, the power is:
At this time, an external absorption resistor is required, and the minimum power is 150.72
watts. In order to reasonably control the temperature rise of the external absorption resistor, the
recommended minimum power of this resistor is 300 watts.
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