NORDAC FLEX (SK 200E ... SK 235E) – Users Manual for Frequency Inverters
80
BU 0200 en-US-4920
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2.6.1.3
Maximum output voltage and torque reduction
As the maximum achievable output voltage depends on the pulse frequency to be set, in some cases
the torque which is specified in document
must be reduced for values above the rated pulse
frequency of 6 kHz.
For F
pulse
> 6 kHz:
T
reduction
[%] = 1 % * (F
pulse
– 6 kHz)
Therefore, the maximum torque must be reduced by 1% for each kHz pulse frequency above 6 kHz.
The torque limitation must be taken into account when reaching the breaking frequency. The same
applies for the degree of modulation (P218). With the factory setting of 100%, a torque reduction of
5% must be taken into account in the field reduction range:
For P218 > 100%:
T
reduction
[%] = 1% * (105 – P218)
No reduction needs to be taken into account above a value of 105%. However, with values above
105% no increase in torque above that of the Planning Guideline will be achieved. Under certain
circumstances, degrees of modulation > 100% may lead to oscillations and motor vibration due to
higher harmonics.
Information
Power derating
At pulse frequencies above 6 kHz (400 V devices) or 8 kHz (230 V) devices, the reduction in power must be
taken into account for the design of the drive unit.
If parameter (P218) is set to < 105%, the derating of the degree of modulation must be taken into account in the
field weakening range.
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2.6.1.4
Commissioning information
For zone 22 the cable inlets must at least comply with the IP55 rating. Unused openings must be
closed with blank screw caps that are suitable for ATEX zone 22 3D (generally IP66).
The motors are protected from overheating by the device. This takes place by means of evaluation of
the motor PTC thermistor (TF) on the device. In order to ensure this function, the PTC thermistor must
be connected to the intended input (terminal 38/39).
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In addition, make sure to use a NORD motor from the motor list (P200). If a standard 4-pole NORD
motor or a motor from a different manufacturer is not used, data for the motor parameters ((P201) to
(P208)) must be adjusted to those on the motor nameplate.
The stator resistance of the motor (see
P208) must be measured by the inverter and at ambient temperature. To do this, set parameter P220
to 1.
In addition, parameterize the variable frequency drive so that the motor can be operated with a
maximum speed of 3000 rpm. For a four-pole motor, set the maximum frequency to a value that is
less than or equal to 100
Hz ((P105) ≤ 100). Adhere to the maximum permissible output speed of the
gear unit here. In addition, switch on I²t motor monitoring (parameter (P535)/(P533)) and set the pulse
frequency to between 4 kHz and 6 kHz.
