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160 Powerdrive F300 User Guide
Issue Number: 2
8.3 Switching frequency
The default switching frequency is 3 kHz, however this can be increased up to a maximum of 16 kHz by Pr 05.018 (dependent on drive size). The
available switching frequencies are shown below.
Table 8-1 Available switching frequencies
If the switching frequency is increased from 3 kHz the following apply:
1. Increased heat loss in the drive, which means that derating to the output current must be applied.
See the derating tables for switching frequency and ambient temperature in section 12.1.1 Power and current ratings (Derating for switching
frequency and temperature) on page 232.
2. Reduced heating of the motor - due to improved output waveform quality.
3. Reduced acoustic noise generated by the motor.
4. Increased sample rate on the speed and current controllers. A trade off must be made between motor heating, drive heating and the demands of
the application with respect to the sample time required.
Table 8-2 Sample rates for various control tasks at each switching frequency
8.4 High speed operation
8.4.1 Field weakening (constant power) operation
(Open loop and RFC-A mode only)
The drive can be used to run an induction machine above synchronous speed into the constant power region. The speed continues to increase and
the available shaft torque reduces. The characteristics below show the torque and output voltage characteristics as the speed is increased above the
rated value.
Fire Mode - Important Warning.
When Fire Mode is active the motor overload and thermal protection are disabled, as well as a number of drive protection functions. Fire
Mode is provided for use only in emergency situations where the safety risk from disabling protection is less than the risk from the drive
tripping - typically in smoke extraction operation to permit evacuation of a building. The use of Fire Mode itself causes a risk of fire from
overloading of the motor or drive, so it must only be used after careful consideration of the balance of risks.
Care must be taken to prevent inadvertent activation or de-activation of Fire Mode. Fire Mode is indicated by a flashing display text
warning "Fire mode active".
Care must be taken to ensure that parameters Pr 01.053 or Pr 01.054 are not inadvertently re-allocated to different inputs or variables. It
should be noted that, by default, Pr 01.054 is controlled from digital input 4 and changing Pr 08.024 can re-allocate this digital input to
another parameter. These parameters are at access level 2 in order to minimize the risk of inadvertent or unauthorized changes. It is
recommended that User Security be applied to further reduce the risk (see section 5.9 Parameter access level and security on page 109).
These parameters may also be changed via serial communications so adequate precautions should be taken if this functionality is utilized.
Drive size Model 2 kHz 3 kHz 4 kHz 6 kHz 8 kHz 12 kHz 16 kHz
3
All 99999
99
4
5
6
7
8
9A
9E
10E
11E
3, 6, 12 kHz 2, 4, 8, 16 kHz Open loop RFC-A / RFC-S
Level 1
3 kHz = 167μs 6 kHz = 83 μs
12 kHz = 83 μs
2 kHz = 250 μs
4 kHz = 125 μs
8 kHz = 62.5 μs
16 kHz = 62.5 μs
Peak limit Current controllers
Level 2 250 μs
2 kHz -500 μs
4 kHz - 250 μs
8 kHz - 125 μs
16 kHz - 125 μs
Current limit and
ramps
Speed controller and
ramps
Level 3 1 ms Voltage controller
Level 4 4 ms Time critical user interface
Background
Non-time critical user interface
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