64 Frequency Converters This classifi cation is illustrated in Fig. 2.20 Speed control performance control classifi cation and Fig. 2.21 Torque performance control classifi cation. Here, the response time refers to how long the FC needs to calculate a corresponding signal change to its output when there is a signal change at the input. The motor characteristics determine how long it takes to register a response on the motor shaft when an input signal is applied to the input of the FC. [ms] 1 Reaction time 10 100 Simple Precision: Speed (% of rated speed) 10 1 0.1 0.01 [%] 10 Fig.
2.20 Speed control performance control classifi cation The rated motor speed is used as the basis for establishing the speed accuracy. The rated motor speed is 50 Hz in most countries, and 60 Hz in the US. FCs can be classifi ed according to price/performance ratio. That is, a FC that uses a simple control method is better value for money for performing very simple tasks, than one featuring fi eld-oriented control. [ms] Flux-vector without feedback 0.1 Reaction time 1 10 Space vector with feed-back 100 Scalar with compensa- tion al ar ar ar ar a it wit wit wit wit wit wit h Precision: Torque (% of rated torque) 100 10 1 0.1 [%] Fig.
2.21 Torque performance control classifi cation Servo Servo Flux vector with feedback Servo Flux vector wo. feedback feedb Space vector feedb Scalar with compensatio Servo -vector Flux-vecto with feed-back Flux-vecto with feed-back -vecto ace vector thout Space vector without feedback ace vector thout