# .Spot.DrivesDC.Partials.Synchron3rd_bldc

## Information

The model is valid for permanent magnet (excite=2) machines.

For rectangular voltage without additional PWM the only degree of freedom is the voltage phase. It is chosen such that the d-axis current (magnetising current) is zero i_s = 0.
Under theese assumptions the torque-speed characteristic is different from that of a DC-machine. In order to obtain a 'true' DC-characteristic with linear dependence of torque and i_s from w_el, a second degree of freedom is needed.

Example using 'average' inverter (approximation of rectangle by its fundamental)
```  v_sd = -w_el*c.L_s*i_s/((4/pi)*sin(width*pi/2)*par.V_nom);
v_sq = 1;
uPhasor = sqrt(v_sd*v_sd + v_sq*v_sq);
uPhasor = atan2(v_sq, v_sd);
```

For reluctance (excite=3) machines psi_e is replaced by a desired magnetising current in d-axis i_sd.

```  uPhasor = atan2(c.R_s*i_s + w_el*c.L_s*i_sd, c.R_s*i_sd - w_el*c.L_s*i_s);
```
Using a pu-current i_sd_pu we obtain
```  uPhasor = atan2(c.R_s*i_s + w_el*c.L_s*i_sd, (par.V_nom/(c.omega_nom*c.L_s))*i_sd_pu - w_el*c.L_s*i_s);
```