every power supply, which is to be introduced around the three phase wires of the AC-Line. In some
cases it might be beneficial to insert further blocking ferrites (6) into the DC-Bus pairs. If doing so, make
sure, every DC-Bus output of the power supply gets its own ferrite to prevent overheating of the ferrite.
Other combinations of motors and cable might require a single stage line EMC filter or an insulated
transformer between 3x400V line-in and TP350.
3.7 Overvoltage
A system of a motor coupled with a load has a certain amount of energy. This energy is mainly kinetic
when the load is moving or rotating. While stopping these loads, the energy must either be stored or
dissipated. The same applies during moves when gravitational energy or spring energy is involved.
The drives recuperate this energy back to the power supply and the bridge voltage rises.
Internal brake capability
The following measures are provided internally of the power supply to store and dissipate energy. The
internal capacitors can store a certain amount of energy
Ec = 0.5 * C * (U2 - UdcSupply2)
Since the maximum voltage is given, the energy stored is defined by the rectified supply voltage UdcSupply.
See technical specification sheet.
Above UBrake-I, the internal brake will be activated to dissipate energy. This resistor can dissipate a short
term energy Eb but only a small continuous power Pb. If an external brake is missing or not properly de-
signed and high mechanical energy is involved the internal brake resistor might reach its thermal limit.
It will turn off and the DC-bus voltage might increase further until the drives turn off. Then the axis does
not stop and might cause mechanical damage.
This failure is avoided by adding an external brake resistor or reducing the deceleration of the drives.
Slower stopping reduces the load on the brake resistor. See section RS232 communication on how to
measure the internal state of the brake resistor.
External brake resistor
The external brake resistor must be dimensioned properly to account for the amount of energy to be
dissipated in the axis system if the internal resistor is not sufficient.
It is recommended to use a resistor that is protected against overtemperature. Contact manufacturer
for dimensioning.
Overvoltage protection
If the external braking resistor is not dimensioned properly, the DC-bus voltage may exceed the limit U d-
cMax. The drives will not be damaged because they protect themselves by turning off their semiconduct-
or switches. The axis is not decelerated anymore and the voltage will not increase any further. However,
turning off the drives during fast motion leaves the axis at the original speed. The axis might crash into
its end-limits, which might cause significant mechanical damage to the mechanical system.
Therefore it is important to choose a well dimensioned braking resistor. Also, the overvoltage error
message of the drives may be used by the control system for further information.
6 Würth 742 7010 or similar.
HWTP150-TP350_B_HardwareManual_EP017 2014-04-01 9/13
