EA180 Servo Drive Manual
6
Chapter 2 Installation
2.1 Selection of braking resistor
When the output torque of the motor is in reverse direction, the energy is transmitted back from the load to the drive. This energy
will be injected into the capacitors of the bus bar, so that the voltage of the bus inside the drive rises, and the size of the recharging
energy depends on the inertia of the rotor and the load of the motor. If the system inertia is small, possibly through capacitor to drive the
internal recirculation of energy absorption, but if the system inertia is large, more than the capacity to absorb the energy, then the voltage
value may rise too high, causing the drive stop or even damage, so when the voltage rises to a certain value, the recharge energy must be
consumed by brake resistance.
The following table 2-1 lists the rotor inertia of the commonly used SER series servo motors and the capacity of the internal
absorption of EA180 servo drive, as well as the formula for the calculation of the regenerative energy.
Table 2-1 Rotor inertia of commonly used SER series servo motors and capacitor absorbable regenerative energy
The regenerative energy from rated
speed to 0 with no load
Eo (Joule)
The maximum regenerative
energy of capacitor
Ec (Joule)
Calculation formula of regenerative energy：
（Joule） V：rpm，motor’s rated speed
The difference in rotor inertia between a servomotor with a brake and a servomotor without a brake is little, and can be
considered the same.
2.2 Built in braking resistor
EA180 series drive starting from 5R5 contains a braking resistor that is suitable for general load inertia. Table 2-2 is the
specifications for EA180 series built-in brake resistors.
Table 2-2 EA180 Built in brake resistance and Allowable minimum external resistance
Built in brake resistor specifications
Built in brake resistance,
handling capacity
Allowable minimum
external resistance
2.2.1 External braking resistance capacity calculation formula
When the regenerative capacity exceeds the handling capacity of the built in braking resistance, alarm Al017 occurs, should
apply to external braking resistance.
According to the calculation formula of the retrogradation of energy, assuming total load inertia is N times the inertia of the
rotor of the motor, brake motor is braked from the rated speed to 0, regenerative energy is N *Eo, the action cycle is T(S),
then, the power of brake resistance= 2[Nx Eo-Ec]/T
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