52 Guidelines for planning the electrical installation
Selecting the supply disconnecting device
Install a hand-operated input disconnecting device between the AC power source and the
drive. The disconnecting device must be of a type that can be locked to the open position
for installation and maintenance work.
European Union
To meet the European Union Directives, according to standard EN 60204-1, Safety of
Machinery, the disconnecting device must be one of the following types:
• switch-disconnector of utilization category AC-23B (EN 60947-3)
• disconnector that has an auxiliary contact that in all cases causes switching devices to
break the load circuit before the opening of the main contacts of the disconnector
(EN 60947-3)
• circuit breaker suitable for isolation in accordance with EN 60947-2.
Other regions
The disconnecting device must conform to the applicable safety regulations.
Selecting the main contactor
If a main contactor is used, its utilization category (number of operations under load) must
be AC-1 according to IEC 60947-4, Low-voltage switchgear and controlgear. Select the
contactor according to the nominal voltage and current of the drive.
Examining the compatibility of the motor and drive
Use an AC induction motor with the drive. Several induction motors can be connected at a
time.
Select the motor size and drive type from the rating tables in chapter Technical data on
basis of the AC line voltage and motor load.
Make sure that the motor withstands the maximum peak voltage in the motor terminals,
see the Requirements table on page 53. For basics of protecting the motor insulation and
bearings in drive systems, refer to section Protecting the motor insulation and bearings
below.
Note:
• Consult the motor manufacturer before you use a motor which nominal voltage differs
from the AC line voltage connected to the drive input.
• The voltage peaks at the motor terminals are relative to the supply voltage of the drive,
not the drive output voltage.
Protecting the motor insulation and bearings
The drive uses modern IGBT inverter technology. Regardless of frequency, the drive
output has pulses of approximately the drive DC bus voltage with a very short rise time. Up
to twice bus voltage can be at the motor terminals, depending on the attenuation and
reflection properties of the motor cable and the terminals. The increased voltage 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. This can
gradually erode the bearing races and rolling elements.
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