Jetter JM-105, User Manual, Page: 46 / 106

7 Description of Connections
46 Jetter AG
7.1.3 Recommendations on preventing
overvoltage at braking or lowering a
vertical load
At fast braking or reversing the axis motion, the braking energy is fed back to the
motor power supply. This can cause the DC link voltage to increase. If the voltage
has reached a limit of 60 V, the overvoltage error is recognized and the motor control
deactivated. There are two ways of preventing overvoltage:
Possibility # 1:
Connecting an external capacitor:
The external capacitor must be able to take up the back-fed energy.
The capacitor must be designed for a voltage of at least 100 V.
Designing an external capacitor:
Where:
U
Max
= 60 V
C
Int
= 200 µF
U
Nom
= 48 V
E
M
: back-fed energy [J]
Calculating the braking energy in case of a rotatory motor:
Where:
J
M
: Inertia of the motor [kgm
2
]
J
L
: Inertia load of the motor [kgm
2
]
n
M
: Motor speed before deceleration [1/s]
m
L
: Mass of the load at non-horizontal motion [kg]
g = 9.81 m/s
2
h
1
: Height before deceleration [m]
h
2
: Height after deceleration [m]
I
M
: Motor current during deceleration [A]
R
Ph
: Resistance of the motor [ ]
t
d
: Delay time [s]
M
L
: Friction torque of the motor [Nm]
C
2E
M
U
Max
2
U
Nom
2
–
----------------------------- C
Int
– =
E
M
1
2
---
J
M
J
L
+
( )
2
π
n
M
m
L
g h
1
h
2
–
( )
3I
M
2
R
Ph
t
d
–
M
L
t
d
π
n
M
– + =
Kinetic energy Potential energySwitching losses Friction
Ω