Datasheet

AD2S1205
Rev. A | Page 8 of 20
RESOLVER FORMAT SIGNALS
06339-003
V
r
=
V
p
× Sin(ωt)
V
b
= V
s
× Sin(ωt) × Sin(θ)
(A) CLASSICAL RESOLVER
S1 S3
V
a
= V
s
× Sin(ωt) × Cos(θ)
S2
S4
R1
R2
θ
V
r
=
V
p
× Sin(ωt)
V
b
= V
s
× Sin(ωt) × Sin(θ)
(B) VARIABLE RELUCTANCE RESOLVER
S1 S3
V
a
= V
s
× Sin(ωt) × Cos(θ)
S2
S4
R1
R2
θ
Figure 3. Classical Resolver vs. Variable Reluctance Resolver
A classical resolver is a rotating transformer that typically has a
primary winding on the rotor and two secondary windings on
the stator. A variable reluctance resolver, on the other hand, has the
primary and secondary windings on the stator and no windings
on the rotor, as shown in Figure 3; however, the saliency in this
rotor design provides the sinusoidal variation in the secondary
coupling with the angular position. For both designs, the resolver
output voltages (S3 − S1, S2 − S4) are as follows:
SinθtSinES1S3
0
×ω=− )( (1)
CosθtSinES4S2
0
×ω=− )(
where:
θ is the shaft angle.
Sin(ωt) is the rotor excitation frequency.
E
0
is the rotor excitation amplitude.
The stator windings are displaced mechanically by 90° (see
Figure 3). The primary winding is excited with an ac reference.
The amplitude of subsequent coupling onto the 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 the shaft angle. Resolver format signals refer to the
signals derived from the output of a resolver, as shown in
Equation 1. Figure 4 illustrates the output format.
06339-004
0°
S2 – S4
(COSINE)
S3 – S1
(SINE)
R2 – R4
(REFERENCE)
90° 180°
θ
270° 360°
Figure 4. Electrical Resolver Representation