Resolver Fundamentals

Resolvers are absolute rotary position transducers. They are very simple and robust, can be very accurate, and, in some cases, inexpensive. A wide variety of resolvers are available in many configurations and for various applications.

Resolver feedback is supported by the RMC150 Resolver (R) and Resolver (RW) modules.

The RMC150 Resolver module supports the following resolver options:

Resolver Options	Resolver (R) - Standard	Resolver (RW)
Resolution	14 or 16 bits	14 or 16 bits
Reference Frequency	800Hz to 5kHz (generated by RMC)	400Hz (externally generated)
Reference Amplitude	1.42 to 4.80 V RMS (generated by RMC)	26 V RMS (externally generated)

Contact Delta for other options.

How Resolvers Work

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. This signal is called the Reference Signal and is generated by the RMC. The position measurement of the resolver is determined by the ratio of the amplitudes of the signals on the secondary windings and their phase with respect the signal on the primary winding (the reference signal).

Important Resolver Specifications

Resolvers are commercially available in many varieties with different specifications. The primary specifications of interest as applied to the RMC are:

Frequency
The frequency of the Reference Signal driving the primary winding.
Voltage
The specified voltage of the Reference Signal driving the primary winding.
Output Voltage
The output voltage from the secondary windings or the transformation ratio between primary and secondary windings.

The RMC Resolver module is designed to work with only a subset of all resolver types available. The Resolver Module 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.

Setting Up the Resolver Module

Wire the resolver according to the RMC150 Resolver Wiring topic.
Set the following parameters:
Scale the axis. Typically, resolvers will use Rotary Scaling. Notice that one revolution of the resolver will always consist of 65,536 counts on the RMC, regardless of the resolver resolution parameter.