Design Guide | iC2-Micro Frequency Converters Electrical Installation Considerations
See EN/IEC61800-5-1 for further information.
7.7 Motor Installation
7.7.1 Motor Installation Considerations
When selecting an AC drive, consider the following aspects:
l Torque limits: When an AC drive controls a motor, torque limits can be set for that motor. Selecting a frequency converter with an
apparent power rating that matches the rated current or power of the motor ensures that the required load can be driven reliably.
However, an extra reserve is necessary to enable smooth acceleration of the load and also cater for occasional peak loads.
l Current ratings of the drive and the motor. Power rating is only a rough guide.
l Correct operating voltage.
l Ensure that the motor withstands the maximum peak voltage on the motor terminals.
l Required speed range: Operation above nominal motor supply frequency (50Hz or 60Hz) is possible only at reduced power.
Operation at low frequency and high torque can cause the motor to overheat due to lack of cooling.
l Derating: Synchronous motors require derating, typically by 2–3 times, because the power factor, and hence the current, can be
high at low frequency.
l Overload performance: The drive limits current to 150% of full current quickly. A standard, fixed-speed motor tolerates these
overloads.
l Stopping the motor: If it is necessary to stop the motor quickly, using a brake resistor should be considered (select braking
terminals on iC2-Micro Frequency Converters) to absorb the energy.
l The direction of rotationwhen connected to the frequency converter's output terminals U-V-W follows the specification from
NEMA MG1 and IEC 60034-8. Ensure correct direction of rotation in the end application to avoid a potential hazardous situation. If
only 1 direction of rotation is required, it is recommended to parameterize the drive to operate in the relevant direction only.
For the basics of protecting the motor insulation and bearings in AC drive systems, see 7.7.3 Motor Insulation and 7.7.4 Bearing Currents.
7.7.2 Supported Motor Types
The iC2-Micro Frequency Converters are compatible with:
l Asynchronous AC induction motors.
l Synchronous permanent magnet motors.
The drives are motor-independent, and can be connected to any brand of motor. For instructions on how to set up motors, refer to the
application guide.
For detailed information about the supported motor types, contact Danfoss.
7.7.3 Motor Insulation
Because of rapid switching and reflections in the cables, motors are subject to more voltage stress in the windings when fed by AC drives
than with sinusoidal supply voltage.
Regardless of frequency, the AC drive output comprises pulses of approximately the drive DC-bus voltage with a 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 stresses the motor winding insulation and can cause it to break down, resulting in possible sparking.
Depending on voltage and cable length, a filter or reinforced insulation of the motor is required.
7.7.4 Bearing Currents
AC drives can cause common-mode voltages which induce voltages across motor bearings, leading to current flow through motor
bearings. To protect against bearing currents, use either sine-wave filters or common-mode filters.
Danfoss A/S © 2024.08 AJ402315027937en-000401 / 130R1239 | 85
To Next Page
Loading...
