Rockwell Automation SA500 AC Power Modules - Manual (Page 26)

3-2 SA500 Power Modules
The PMI will automatically request its operating system from the UDC module as soon
as communications are established over the fiber-optic link. After the operating system
has been downloaded from the UDC module (a process that takes approximately 0.5
seconds), the PMI Regulator will send a feedback message. The UDC module will
respond with a command message and configuration data. The information sent
contains configuration data as well as the synchronization information necessary for
the PMI to determine when to send feedback messages to the UDC module once
UDC application tasks are put into run.
The PMI uses non-volatile EPROM memory to store the initial start-up software and
power-up diagnostics and to establish communication with the UDC module. After
power-up, the module stores data in and operates out of volatile SRAM. If power is
removed from the Power Module, all data and the module’s operating system will be
lost. When power is returned to the Power Module, the PMI module will begin its
normal power-up routine.
3.2 DC-to-DC Converter
A DC-to-DC converter in the Power Module provides the DC voltages necessary for
the operation of the PMI. The converter is connected to DC input power internally
when the Power Module is connected to the DC Bus Supply.
The PMI monitors the +5V and the +/-15V supplied via the converter. When these
voltages are above specified levels, the PMI will turn on the PWR OK LED. If the +5V
line falls below a pre-determined level, the PMI turns off power to the gate drivers
under hardware control, and the motor coasts to a stop.
3.3 Resolver Interface
The resolver interface converts analog sine and cosine resolver feedback signals into
digital format. A tracking ratiometric resolver-to-digital (R/D) converter outputs a 12- or
14-bit digital number indicating the absolute electrical position of the resolver shaft.
The resolution (12 or 14 bit) of the R/D converter is selected during drive parameter
entry. A two-bit revolution counter extends operation over four electrical revolutions.
The counter is reset whenever power is turned on to the system or a system reset
command is asserted by the PMI. When 12-bit mode is selected, the resolver data
format will be as shown in figure 3.1. Figure 3.2 shows the resolver data format when
14-bit mode is selected.
Figure 3.1 – Resolver Data Format (12-Bit Mode)
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
bits
revolution counter
resolver data 0 0