2-46
Engineering Guide CDA3000
2 Drive definition
Project planning notes
A synchronous motor, too, is a special motor which must be tested anew
prior to every production deployment. Depending on the situation, smooth
running, heat, noise or vibration problems may occur. The following table
presents a listing of key points which may need to be considered.
Subject Project planning notes
Motor design For precise data refer to the manufacturer’s data specification booklet
Tips:
• Synchronous motors with cage winding can be run on the mains
and on the inverter.
• The synchronous breakdown torque M
ksy
is approx. 1.35 x M
N
.
If a higher breakdown torque is required (e.g. 1.6 times), a hig-
her-powered motor must be chosen.
• The external moment of inertia specified by the manufacturer
must not be exceeded, otherwise the motor will not be able to
generate the acceleration torque required for synchronization.
• At low frequencies the no-load current may be higher than the
load current.
• Motor protection only possible via PTC
• High tendency to vibrate
Inverter design In static operation with manipulating range <
1:5 (20-100 Hz)
• I-Inverter ~ I
N
Motor
In static operation with manipulating range <
1:5 (5-100 Hz)
• I-Inverter ~ 1.2 x I
N
Motor
With group drive
• Refer to the “Multi-motor operation” project planning notes,
section 3.3. The startup currents for connection of the motor to
max. frequency may be 30 times the motor rated current.
• V/F characteristic with at least three programmable interpolation
points
• Shut down the slip compensation, load compensation and V/F
characteristic adaptation software functions
For rapid synchronization the motor should be run in the frequency
range to 50 Hz with current injection. In individual applications it will
be necessary to stop the acceleration process for 10 s at 5 Hz to allow
the motor time to switch to synchronous mode.
Table 2.14 Project planning notes for permanent magnet excited
synchronous motors with cage winding for asynchronous
self-starting.
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