Planning the electrical installation
70
2. Check that the motor voltage rating meets the application requirements:
See section When DC link voltage is increased with parameter settings (page 73).
3. Consult the motor manufacturer before using a motor in a drive system where the
motor nominal voltage differs from the AC power source voltage.
4. Ensure that the motor insulation system withstands the maximum peak voltage in
the motor terminals. See section Requirements for motor insulation and bearings
and drive filters below for the required motor insulation system and drive filtering.
Example: When the supply voltage is 440 V, the maximum peak voltage in the
motor terminals can be approximated as follows: 440 V × 1.41 × 2 = 1241 V.
Check that the motor insulation system withstands this voltage.
Protecting the motor insulation and bearings
The drive employs modern IGBT inverter technology. Regardless of frequency, the
drive output comprises pulses of approximately the drive DC bus voltage with a very
short rise time. The pulse voltage can almost double at the motor terminals,
depending on the attenuation and reflection properties of the motor cable and the
terminals. This can cause additional stress on the motor and motor cable insulation.
Modern variable speed drives with their fast rising voltage pulses and high switching
frequencies can generate current pulses that flow through the motor bearings, which
can gradually erode the bearing races and rolling elements.
Optional du/dt filters protect motor insulation system and reduce bearing currents.
Common mode filters mainly reduce bearing currents.
To avoid damage to motor bearings:
• select and install the cables according to the instructions given in the hardware
manual
• use insulated N-end (non-drive end) bearings and output filters from ABB
according to section Requirements for motor insulation and bearings and drive
filters below.
When … then the motor voltage rating
should be …
DC link voltage is not increased from nominal (through
parameter settings)
U
N
DC link voltage is increased from nominal (through
parameter settings)
U
DC
/ 1.41
U
N
Rated input voltage of drive
U
DC
Maximum DC link voltage of drive in V DC. See the parameter setting. For resistor
braking, U
DC
= 1.21 × nominal DC link voltage. Note: Nominal DC link voltage is U
N
×
1.41 in V DC.
To Next Page
Loading...
