User manual

Chapter 1 Introduction to the 2762-17

ADVANCED MICRO CONTROLS INC.

Brushless Resolver Description

The brushless resolver is unsurpassed by any other type of rotary position transducer in its

ability to withstand the harsh industrial environment. An analog sensor that is absolute over a

single turn, the resolver was originally developed for military applications and has benefited

from more than 50 years of continuous use and development.

The resolver is essentially a rotary transformer with one important distinction. The energy

coupled through a rotary transformer is not affected by shaft position whereas the magnitude of

energy coupled through a resolver varies sinusoidally as the shaft rotates. A resolver has one

primary winding, the Reference Winding and two secondary windings, the SIN and COS

Windings. (See Figure 1.2, Resolver Cut Away View). The Reference Winding is located in

the rotor of the resolver, the SIN and COS Windings in the stator. The SIN and COS Windings

are mechanically displaced 90 degrees from each other. In a brushless resolver, energy is

supplied from the Reference Winding to the rotor by a rotary transformer. This eliminates

brushes and slip rings in the resolver and the reliability problems associated with them.

In general, the Reference Winding is excited by an AC voltage called the Reference Voltage

). (See Figure 1.3, Resolver Schematic). The induced voltages in the SIN and COS

Windings are equal to the value of the Reference Voltage multiplied by the SIN or COS of the

angle of the input shaft from a fixed zero point. Thus, the resolver provides two voltages

whose ratio (SIN / COS = TAN , where  = shaft angle) represents the absolute position of the

input shaft. Because the ratio of the SIN and COS voltages is considered, any changes in the

resolvers’ characteristics, such as those caused by aging or a change in temperature, are

ignored.

R1 Red Wht

R2 l Wht

Winding

4 lu

2 el

3 l

1 Red

Winding

Rotary

Transformer

Wire Color

Fig 1.3 Resolver Schematic

SIN and COS W indings

Reference Winding

Fig 1.2 Resolver Cut away View