The five most important factors to consider when specifying the proper resolver for your application include: input voltage, input current, transformation ration, size of resolver, speed of resolver.

• Input Voltage - In general, resolvers take an input voltage from 0.5 to 115 Vrms (60 Hz to 100 kHz). It is important not to exceed the recommended input current; otherwise the iron core may saturate.
• Input Current - The maximum input current is the current in amps that is required to energize the primary winding at the system input voltage and frequency. For a given resolver winding and input voltage, the resolver will draw a specified current. This current will vary slightly depending on small variations in wire diameter, and on changes to drive voltage. 
• Transformation ratio
• Size of resolver – outer diameter of the housing and the attachment type (frameless vs housed)
• Speed of resolver