20 Gear Drive, Plymouth Ind. Park, Terryville, CT 06786
Tel: (860) 585-1254 Fax: (860) 584-1973 http://www.amci.com
7
I
NTRODUCTION
TO
THE
RD750
The RD750
For over twenty years, Rockwell Automation and
Advanced Micro Controls Inc. have partnered
together to offer the most advanced sensor interface
technology on the market. Based on this long
standing relationship, AMCI is proud to announce
the first and only resolver interface module for the
PowerFlex 750-Series AC Drives from Rockwell
Automation.
Utilizing advanced resolver to digital conversion
technology, the RD750 can interface with a wide
variety of resolvers, including those from AMCI,
Moog, Reliance, and Tamagawa, as well as many
others.
R-D Converter
The heart of the resolver-to-digital converter is a
monolithic IC that utilizes a ratiometric, Type II
tracking loop converter for high speed data acquisi-
tion without velocity induced errors.
To be as accurate as possible, the monolithic R/D converter requires a very specific return voltage from the
sine and cosine windings, as well as minimal phase shift between the reference voltage and these return sig-
nals. The RD750 has additional hardware to guarantee R/D conversion accuracy.
Analog Buffer:
The analog buffer presents a specific load to the resolver. This load prevents the mag-
netic cores of the resolver from saturating if it is operated at a voltage higher than its published specifi-
cation. (A resolver can always be operated at a lower voltage without accuracy concerns.)
Analog Multiplier:
On power up, or when the RD750 receives a reset signal from the drive, the card
reads the sine and cosine return voltages multiple times for approximately sixty milliseconds. With
these readings, the RD750 calculates the proper coefficient for an analog multiplier that adjusts the sine
and cosine signals so they are optimized for the monolithic R/D converter.
Phase Compensator:
The readings that are used to set the analog multiplier are also used by the
RD750 to determine the phase shift between the reference voltage and the return signals. Once this
value is known, the RD750 generates a second reference signal that is identical in frequency to the first
reference, but phase shifted by the proper amount. The first reference voltage signal drives the resolver.
The second reference is fed into the R/D converter. To the R/D converter, the reference and return sig-
nals appear to be in phase, yielding a more accurate conversion.
The RD750 offers multi-turn position feedback with a single turn position resolution of up to 65,536 counts
per turn and a tracking rate of up to 150,000 RPM. In addition to the single resolver interface, the RD750
offers an A/B quadrature output with Z pulse, powered by differential output drivers. These drivers are
jumper selectable for 5 or 12 Vdc operation.
The module’s basic configuration is accomplished with a bank of ten DIP switches located on the board. The
parameters set with these switches are:
Transformation Ratio:
Thirteen settings that cover a range of 0.15 to 1.75
†
Reference Frequency:
Fifteen settings from 2.0 to 20.0 kHz
Resolver Position Resolution:
Settings of 10, 12, 14, or 16 bits per turn
† In order to control the level of the return signals, Transformation Ratio is a more important setting to the RD750 then
setting the level of the reference voltage. Setting the TR sets the reference voltage between 3.75 and 15.00 Vrms.
