Delta RMC101 User Manual
Page 604
RMC100 and RMCWin User Manual
6-60
Resolvers are rotary transformers with one primary winding and two secondary windings. The
primary winding is generally on the rotor and the two secondary windings are on the stator. The
secondary windings are arranged 90 degrees from each other such that when one is lined up with
the rotor winding (full coupling) the other is at a right angle (no coupling).
The primary winding is driven with an alternating current signal at a specified voltage and
frequency. The position measurement is determined by the ratio of the amplitudes of the signals
on the secondary windings and their phase with respect to the primary signal.
The RMC100 Resolver Interface Module
Resolvers are commercially available in many varieties with different specifications. The primary
specifications of interest as applied to the RMC are:
a. Frequency
The frequency of the signal driving the primary winding.
b. Voltage
The specified voltage of the signal driving the primary winding.
c. Output Voltage
The output voltage from the secondary windings or the transformation ratio between primary and
secondary windings.
The RMC resolver interface card is designed to work with only a subset of all resolver types
available. The Resolver Specifications topic lists the range of values compatible with the standard
RMC Resolver module. In addition, a wider range of resolvers can be used by modifying
components on the interface card module or by using external reference generators to drive the
primary winding. Contact Delta for more details.
Determining Absolute Position
There are several conditions when the resolver axis establishes its absolute position within one
turn of the resolver. These conditions are:
• On power-up
• After a transducer fault
• After a Reset Position command
• After a Set Parameters command if the Scale or Coordinate Limit parameters have changed
The axis determines its absolute position as follows.
1. The 16-bit value read from the resolver is added to the Count Offset
2. If the result is outside the range of -32768 to +32767 then 65536 is added or subtracted to force
it into the range. (This is the range that can be represented by a 16 bit number.)
3. This value is converted to Position Units:
Position Units = Scale x Counts / 32768