Table 4 Steady-state eigenvalues

5th Mode

(− 0.4633 ± 295.19i)/1.60205e−03

(− 2.7521 ± 295.18i)/9.32305e−03

(− 3.32561 ± 295.17i)/1.1266e−02

4th Mode

(− 1.1478 ± 200.68i)/5.71946e−03

(− 3.1478 ± 200.66i)/1.56853e−02

(− 4.2164 ± 200.65i)/2.1009e−02

3rd Mode

(− 2.3695 ± 159.51i)/1.48532e−02

(− 4.3578 ± 159.50i)/2.73114e−02

(− 5.3785 ± 159.51i)/3.3699e−02

2nd Mode

(− 3.1452 ± 124.39i)/2.52769e−02

(− 5.7569 ± 124.38i)/4.62352e−02

(− 6.1982 ± 124.37i)/4.9775e−02

1st Mode

(− 1.1596 ± 97.26i)/1.19218e−02

(− 4.5987 ± 97.24i)/4.72394e−02

(− 5.4462 ± 97.21i)/5.5937e−02

0th Mode

(− 1.3215 ± 5.10i)/2.50832e−01

(− 4.1634 ± 5.09i)/6.33133e−01

(− 5.25641 ± 5.08i)/7.1906e−01

Other mode

Stable

Stable

Stable

Electric mode-eigenvalue/damping ratios

Electrical-mode

(− 0.0756 ± 191.69i)/3.94386e−04

(− 3.2685 ± 190.23i)/1.71792e−02

(− 5.9634 ± 190.21i)/3.13362e−02