SM-Resolver User Guide 13
Issue Number: 4 www.controltechniques.com
4.4 Wiring, Shield connections
Shielding considerations are important for PWM drive installations due to the high
voltages and currents present in the output circuit with a very wide frequency spectrum,
typically from 0 to 20 MHz.
The sensitivity of various inputs to electromagnetic disturbance differs with the
introduction of shielding providing good data transfer. Circuits at particular risk are
precision analog inputs, where quite small induced voltages may cause significant
errors, and fast data or encoder inputs where the signal levels are relatively high but the
bandwidth is wide so that very brief excursions may cause errors.
Table 4.2 Feedback Device Properties
It is also necessary to provide the correct shielding arrangement in order to meet the
radiated emission requirements of EMC standards.
4.4.1 Functional shielding requirements
These requirements are necessary to ensure the correct transfer of data from the
resolver to the drive.
Figure 4-4 Functional shielding requirements
Note that the resolver provides inherent galvanic isolation of the signal connections from
ground. This means that no special provisions are required in order to provide surge
immunity for cables exceeding 30m.
Input Type Nature Wiring Requirement
Resolver Inputs
Medium bandwidth e.g. 10kHz,
sensitive
Shielding recommended
Encoder Inputs
Wide bandwidth e.g. 500kHz.
Good immunity but limited
common mode range
Correct shielding arrangement essential.
Matched cable and correct termination
recommended.
Data links/
comms port
Wide bandwidth for advanced
communications systems, e.g.
500kHz to 10MHz.
Good immunity but limited
common mode range.
Correct shielding arrangement essential/
Matched cable and correct termination
recommended with no discontinuity.
Cable
Cable
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