ABB ACS 502 Series, Инструкция по установке и запуску, Страница: 20 / 92

Chapter 2 – Overview of the ACS 502/504
2-6 ACS 502 Installation & Start-up Manual
General Information
About Your ACS 502/504
Functional Description
Power-on sequence
When line voltage is switched on, the capacitor bank is charged first via the
charging circuit. The charging takes less than one second. During this time,
the thyristors on the rectifier bridge are not conducting.
GENERAL WARNING! The maximum permissible number of chargings in
one minute is four. If the DC bus is charged more often, the charging resistor
may fail due to excess heat. Therefore, it is recommended that you do not use
the input power switching on and off as a Start/Stop command.
The power supply of the ACS 504 comes from the capacitor bank. The power
supply turns on when the voltage on the capacitors has reached about
300 VDC. Subsequently, the Control Interface Card, Motor Control Card and
Main Circuit Interface Card are energized.
When the DC-voltage has reached 80% of its nominal value, the
microprocessor on the Motor Control Card energizes the Input Protection
Card. The thyristors are gated fully conducting and the thyristor-diode
rectifier behaves like a normal 6-pulse diode bridge.
The cooling fan turns on at initial power-on. To prolong the useful life of the
fan bearings, the fan is automatically turned off after one minute, unless:
• The drive has a RUN command, or
• Heatsink temperature is above 113
°
F (45
°
C).
Control
In normal duty the drive follows commands and references either from the
keypad or the terminal block on the Control Interface Card. The control signal
source selection and the way the drive interprets these signals are configured
by parameters.
Power section Power flow through the drive in normal duty is from AC-input line through
the rectifier bridge to the DC-filter capacitors which sustain a constant DC-
voltage. The nominal value for this voltage is 1.35 x V
IN
.
The Inverter consists of six power semiconductor switches whose operation is
controlled by the Motor Control Card via the Main Circuit Interface Card.
Turning these switches on and off in a certain sequence is called modulation.
The modulation frequency in the ACS 504 is about 3 kHz at maximum and
cannot be altered.
The potential at any terminal U
2
, V
2
, W
2
(T
1
, T
2
, T
3
) of the inverter can only
be high or low. The modulation determines which one. At any instant, the line
to line output voltage is either 0 V when the switches in these phases are in the
same position or
±
1.35 x V
IN
when the corresponding switches are in
different positions.