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2.15 Regenerative resistor selection and connections
The use of regenerative resistor
When the motor opposes the direction of rotation as in deceleration or vertical axis
escalation, part of the regenerative energy will be delivered back to the driver. This energy
will first be stored in internal capacitors of the driver. When the energy stored in the
capacitors reach the maximum capacity, a regenerative resistor is required the excessive
energy to prevent over-voltage.
Selection of regenerative resistor
EL8-EC series servo drives are equipped with internal regenerative resistor. If an external
resistor is needed, please refer to the table below.
Internal regenerative resistor
Model no.
Resistance(Ω)
EL8-EC400
EL8-EC750
EL8-EC1000
Calculation of regenerative resistance under normal operation
Steps:
1. Determine if driver comes with a regenerative resistor. If not, please prepare a
regenerative resistor with resistance value higher than might be required.
2. Monitor the load rate of the regenerative resistor using front panel (d14). Set the driver
on high velocity back and forth motions with high acceleration/deceleration.
3.Please make sure to obtain the value under following conditions: Driver temperature <
60℃, d14<80(Won't trigger alarm), Regenerative resistor is not fuming, No overvoltage
alarm(Err120).
Pb(Regenerative power rating) = Resistor power rating x Regenerative load rate (%)
Please choose a regenerative resistor with power rating Pr about 2-4 times the value of
Pb in considered of harsh working conditions and some 'headroom'.
If the calculated Pr value is less than internal resistor power rating, external resistor is not
required.
R(Max. required regenerative resistance) = (380
Problem diagnostics related to regenerative resistor:
If driver temperature is high, reduce regenerative energy power rating or use an
external regenerative resistor.
If regenerative resistor is fuming, reduce regenerative energy power rating or use an
Power rating(W)
100
50
50
75
50
75
User manual of EL8-EC***F AC Servo
Minimum allowable
Resistance(Ω)
Power rating(W)
50
40
30
2
2
– 370
)/Pr
50
50
75
45
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