94 Unidrive M/HS Frame 5 to 6 Power Installation Guide
Issue Number: 9
5.1.15 Start up time
This is the time taken from the moment of applying power to the drive, to the drive being ready to run
the motor:
Sizes 5 and 6 = 2.5 s
For faster start up time a 24V backup supply can be used, see section 4.5 24 Vdc supply on
page 54.
5.1.16 Output frequency / speed range
Unidrive Mxxx models:
In all operating modes (Open loop, RFC-A, RFC-S) the maximum output frequency is limited to 550
Hz.
Unidrive HSxx models:
In open loop mode the maximum achievable output frequency is 3,000 Hz.
In RFC-A and RFC-S modes, the maximum achievable output frequency is 1,250Hz.
In RFC-S mode the speed is also limited by the voltage constant (Ke) of the motor unless field
weakening operation is enabled. Ke is a specific constant for the servo motor being used. It can
normally be found on the motor data sheet in V/k rpm (volts per 1,000 rpm).
It is recommended that a minimum ratio of 12:1 is maintained between the switching frequency and
the maximum output frequency to maintain the quality of the output waveform. If this minimum ratio is
exceeded, extra motor losses will result due to the increased harmonic content of the output
waveform.
5.1.17 Accuracy and resolution
Speed:
The absolute frequency and speed accuracy depends on the accuracy of the crystal used with the
drive microprocessor. The accuracy of the crystal is 100 ppm, and so the absolute frequency/speed
accuracy is 100 ppm (0.01 %) of the reference, when a preset speed is used. If an analog input is
used the absolute accuracy is further limited by the absolute accuracy of the analog input.
The following data applies to the drive only; it does not include the performance of the source of the
control signals.
Open loop resolution:
Preset frequency reference: 0.1 Hz
Precision frequency reference: 0.001 Hz
Closed loop resolution
Preset speed reference: 0.1 rpm
Precision speed reference: 0.001 rpm
Analog input 1: 11 bit plus sign
Analog input 2: 11 bit plus sign
Current:
The resolution of the current feedback is 10 bit plus sign.
Accuracy: typical 2 %
worst case 5 %
5.1.18 Acoustic noise
The heatsink fan generates the majority of the sound pressure level at 1 m produced by the drive. The
heatsink fan is a variable speed fan. The drive controls the speed at which the fan runs based on the
temperature of the heatsink and the drive's thermal model system.
Table 5-14 gives the sound pressure level at 1 m produced by the drive when running at maximum
normal and heavy duty current and when the heatsink fan is running at minimum speed.
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