AD2S1210CSTZ datasheet(16/37 Pages) AD

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AD2S1210

Rev. A | Page 15 of 36

RESOLVER FORMAT SIGNALS

Vr = Vp × sin(ωt)

Vb = Vs × sin(ωt) × sin(θ)

(A) CLASSICAL RESOLVER

Va = Vs × sin(ωt) × cos(θ)

Vr = Vp × sin(ωt)

Vb = Vs × sin(ωt) × sin(θ)

(B) VARIABLE RELUCTANCE RESOLVER

Va = Vs × sin(ωt) × cos(θ)

Figure 24. Classical Resolver vs. Variable Reluctance Resolver

A resolver is a rotating transformer, typically with a primary

winding on the rotor and two secondary windings on the stator.

In the case of a variable reluctance resolver, there are no wind-

ings on the rotor, as shown in Figure 24. The primary winding

is on the stator as well as the secondary windings, but the saliency

in the rotor design provides the sinusoidal variation in the

secondary coupling with the angular position. Either way, the

resolver output voltages (S3 − S1, S2 − S4) have the same

equations, as shown in Equation 1.

cos

sin

−

(1)

where:

θ is the shaft angle.

Sinωt is the rotor excitation frequency.

E0 is the rotor excitation amplitude.

The stator windings are displaced mechanically by 90° (see

Figure 24). The primary winding is excited with an ac reference.

The amplitude of subsequent coupling onto the stator secondary

windings is a function of the position of the rotor (shaft) relative to

the stator. The resolver, therefore, produces two output voltages

(S3 − S1, S2 − S4) modulated by the sine and cosine of shaft

angle. Resolver format signals refer to the signals derived from

the output of a resolver, as shown in Equation 1. Figure 25

illustrates the output format.

0°

S2 – S4

(cos)

S3 – S1

(sin)

R2 – R4

(REF)

90°

180°

270°

360°

Figure 25. Electrical Resolver Representation

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