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Sin-cos encoders are typically powered by a 5V supply. Therefore it is important to ensure that the
controller is configured to supply 5V on Encoder Vcc. This should be done by setting the encoder
configuration object dictionary entry at 4630
h
.
Resolver
The resolver is a position feedback device which requires a sinusoidal excitation (provided by the
Dragon8 controller). The speed feedback consists of two pairs of signals: a Resolver Sin pair and a
Resolver Cos pair (Figure 19). These signals consist of the excitation frequency modulated by the sin or
cosine (respectively) of the rotor position.
The following issues are important when selecting a resolver: mechanical, environmental and electrical
specification.
• Mechanical specification includes e.g. material; dimensions; max speed; max angular
acceleration; rotor moment of inertia; resistance to shock; resistance to vibration; permitted
axial offset; permitted radial runout (deviation from true circle) of motor shaft.
• Environmental specification includes: max operating temperature (including self-heating); IP
rating.
• Electrical specification includes: number of pole pairs (p); transformer ratio (Rt); angular error
tolerance; residual voltage; recommended input voltage; recommended operating frequency;
maximum primary current.
Regarding mechanical and environmental specification, the user must select a resolver appropriate to the
environment of the application.
Regarding electrical specification, the following features are required of a resolver to work with the
Dragon8:
• Transformer ratio = 0.2 to 0.6
• Excitation frequency = 10kHz
• Excitation voltage = 5Vrms nominal (a resolver specified to 5Vrms or higher will be acceptable)
The controller is able to control motors with multiple pole-pair resolvers (i.e. returning multiple sin and
cosine waves per mechanical rotation). However, it is required that the number of pole pairs in the motor
is an integer multiple of the number of resolver pole pairs.
For example:
• A single pole pair encoder can be used with motors that have 1 pole pair, 2 pole pairs, 3 pole pairs,
etc…
• A 3 pole pair encoder can be used with motors that have 3 pole pairs, 6 pole pairs, 9 pole pairs, etc…
• A 5 pole pair encoder can be used with motors that have 5 pole pairs, 10 pole pairs, 15 pole pairs,
etc...
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