Control Rack - WEG MVW01 User Manual

3.4 CONTROL RACK

Inverter operation:
The inverter uses PWM (Pulsed Width Modulation) modulation technique, in order to produce AC voltage with variable frequency and amplitude,
from the DC link voltage, and make it available to the motor at the output terminals. The connection of the medium voltage cables to the motor
is available via terminals (copper bars). The cable exit is located on the lower front of the inverter panel.
The output current (motor current) is measured using Hall effect CTs in all the three phases, and the current signals are sent to the control
board. The inverter uses the measurements to indicate the current and to perform the control and protection functions of the INVERTER +
MOTOR system.
Pre-charge:
During the power-up, due to the high inrush current that is necessary to load the DC link, a pre-charge in the DC link becomes necessary, and
it is carried out by the rectifier (V1) and the high insulation transformer T2. The pre-charge circuit energizes the primary of this transformer with
220 V. The pre-charge resistors AR1 are also connected to the primary winding of this transformer, but they are installed in the control cabinet.
Only after the pre-charge procedure it becomes possible to close the main circuit breaker.
Auxiliary power supply:
The auxiliary power supply (220 V - 690 V) must be connected to the specific terminal strip located in the control cabinet. The T1 transformer
has taps for different primary voltages and supplies 220 V at the secondary in order to feed the low voltage circuits and the exhausting fans
present in the product.
The control rack A8 is fed with 24 Vdc supplied by the PS24 (A11) power supply, whose input is of 220 Vca 1~or 3~. The control rack is
composed by the Power Supply and Interface Board (PIC); and by 02 control boards: MVC3 and MVC4. The MVC3 board is responsible for
the motor and inverter control, and the MVC4 board performs the user interface tasks. Both boards are fed by low voltages coming from the
PIC board, which also contains optoisolated digital inputs and relay outputs (220 Vac) for internal MVW01 use.
Optional Fieldbus communication and function expansion boards (EBA, EBB or EBC) can be connected to the MVC4 control board. The
connections between the MVC3 board and the power stages are made with fiber-optic cables through the FOI interface boards.
✓
NOTE!
For more information on the boards, refer to the
Figure 3.6: MVW01 standard control rack
Item 2.3.3 MVW01 Electronic Boards on page 2-15
MVW01 WITH 3 LEVELS (3L)
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MVW01 | 3-7
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