Moeller DF6-340 Series - Features of the Frequency Inverters; Selection Criteria

01/02 AWB8230-1413GB
Selection criteria
11
Features of the frequency inverters
The DF6 frequency inverters convert the voltage and frequency of
an existing three-phase supply to a DC voltage and use this
voltage to generate a three-phase supply with adjustable voltage
and frequency. This variable three-phase supply allows infinitely
adjustable speed control of three-phase asynchronous motors.
a Supply through an interference suppressor
Mains voltage U
LN
(EU-rated voltages):
3 AC 400 V, 50/60 Hz
b The bridge rectifiers convert the AC voltage of the electrical supply to
a DC voltage.
c The DC link contains a charging resistor, smoothing capacitor and
switched-mode power supply unit. It allows DC link coupling and the
supply of DC current:
DC link voltage (U
ZK
) = W2 x mains voltage (U
LN
)
d IGBT inverter:
The power inverter converts the DC voltage of the internal DC link to
a variable three-phase alternating voltage with variable frequency.
In conjunction with an external braking resistor, the braking transistor
allows braking of motors with a high moment of inertia or during
extended regenerative operation.
e Output voltage (U
2
), motor connection:
three-phase, variable AC voltage, 0 to 100 % of the input voltage
(V
LN
)
Output frequency (f
2
):
Variable frequency, 0 to 400 Hz
Output rated current (I
2N
):
22 to 253 A at about 1.5 times starting current for 60 s, at a switching
frequency of 5 kHz and at an ambient temperature of 40 °C
Motor connection, assigned shaft output (P
2
):
11 to 132 kW at 400 V
f Programmable control section with LCD keypad and interface
Selection criteria
Select the frequency inverter according to the rated current of the
motor. The rated output current of the frequency inverter must
however, be greater than or equal to the rated current of the
motor.
The following drive data is assumed to be known:
• Type of motor (three-phase asynchronous motor)
• Mains voltage = supply voltage of the motor (e.g. 3 ~ 400 V)
• Rated motor current (guide value, dependent on the circuit type
and the supply voltage)
• Load torque (quadratic, constant, with 1.5 times the starting
torque)
• Ambient temperature (maximum temperature 40 °C).
The rated output current of the frequency inverter can be found in
the technical data in the appendix from page 159.
Figure 5: Function chart of the frequency inverter
a
bc d
f
e
M
3
˜
h
h
If several motors are connected in parallel to the output of
a frequency inverter, the motor currents are subject to
vector addition, i.e. the active in-phase current and
reactive current components are added separately. When
you select a frequency inverter, make sure that it can
supply the total resulting current.
h
If you connect a motor to an operational frequency
inverter, the motor draws a multiple of its rated current.
When you select a frequency inverter, make sure that the
starting current plus the sum of the currents of the
running motors will not exceed the rated output current of
the frequency inverter.
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