9. SPECIFICATIONS
9－55
9.1.16 Regenerative Processing
Although the PY2 (15 A/30 A) has a built-in regenerative processing circuit, no regenerative resistor is
provided. So, externally connect a regenerative resistor as necessary. It is recommended that one be
externally connected when a 300 W or higher motor is to be driven.
Mount it between the P and Y (or COM) terminals of connector CND on the front of the amplifier.
The PY2 (50 A) has a built-in regenerative resistor. However, regenerative power that cannot be absorbed
by the built-in resistor may occur depending on the load inertia or the operating pattern. In such cases,
connect an external regenerative resistor.
Available external regenerative resistors are introduced in 9.5. Select according to your specifications by
referring to the following method of calculating regenerative power PM.
(1) Calculation of regenerative power PM
Step 1 : Calculate the regenerative energy
The following is an example of how to calculate regenerative energy EM.
① For horizontal shaft driving
EM = EHb = × N × 3 • KEφ × × tb – ( )
2
× 3 • Rφ × tb
EM : Regenerative energy at horizontal shaft driving [J]
EHb : Regenerative energy at deceleration [J]
KEφ : Induced voltage constant [Vrms/min
－
1
] (motor constant)
KT : Torque constant [N･m/Arms] (motor constant)
N : Motor speed [min
-1
]
Rφ : Armature resistance [Ω] (motor constant)
tb : Deceleration time [s]
Tb : Torque at deceleration [N･m] (Tb = Tc – TF)
Tc : Acceleration/deceleration torque [N･m]
TF : Friction torque [N･m]
1
2
Tb
KT
Tb
KT
If inertia is large and sudden starting or stopping is applied without a regenerative resistor,
an overvoltage alarm ("5" displayed in the 7-segment LED, alarm code "05H") may be
issued. In this case, externally connect a regenerative resistor (the Servo Amplifier will not
break even if an overvoltage alarm is issued).
On the Servo Amplifier without an external regenerative resistor, the main circuit power
smoothing electrolytic capacitor is not instantaneously discharged when the R, S or T
terminal of the main circuit power is turned off. In this case, allow more than five minutes
after the main circuit power is turned off and make sure that the red LED on the front of the
amplifier, which indicates whether the main circuit power is charged or not, is turned off
(discharged) before removing the amplifier.
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