with variable voltage. Although input voltage fluctuates according to traction output, auxiliary power is stabilized by the GTO thyristor inverter. The configuration of the unit circuit is almost the same as that of the traction inverter.
The smoothing reactor's function is to maintain electrical separation of control influence between input and output. At the reactor input, there is a voltage regulating the controller including alternator exciter circuits, and there are three traction inverters individually controlled by every inverter and microprocessor at the output. Unlike the smoothing reactor, variation of capacitor voltage at the DC circuit is directly related to both alternator voltage regulator and inverter controllers, so separation is necessary to avoid influence.
The three traction inverters with induction motors are essentially controlled independently. Each inverter has a control function both for output voltage and frequency for the traction motor. Motor current and voltage are set to values determined by the operator notch command, satisfying the output torque of the traction motor.
Electrical weight transfer compensation is easily achieved by means of an individual axle control system. At locomotive speeds of up to 40 km/h, the traction motor current for the front axle within a bogie is controlled to be 6% more, and that of the rear axle 6% less, to equalize the adhesive coefficient value of each wheel.
Individual axle control performs re-adhesion control for wheel slip and slide independently for each axle. When a wheel slips, the motor current must be decreased to reduce motor torque for re-adhesion just after the slip is detected. The influence of this torque reduction on the locomotive performance is not great; just enough to reduce the slipped motor current. In this case, if some motors are connected to an inverter in parallel, current reduction for re-adhesion has much more influence on locomotive torque depression.
(2) Performance
Fig. 2.2 shows locomotive performance. Maximum locomotive wheel output power is 1800 kW when two diesel engines generate 2500 kW of power, and auxiliary circuit portion and loss of traction circuits are reduced from the maximum output value.
The maximum output power is 1.5 times greater than that of the conventional DD51 diesel- hydraulic locomotive. The balancing speed in hauling a 1000 ton container train up a 1% gradient was improved from 29 km/h to 47 km/h.
With six driving axles instead of the DD51's four and better re-adhesion control using the individual axle control method described before, the average obtainable adhesive coefficient is more than 0.3 times, and the starting torque, nearly twice as much as that of the DD51. Actual measurements proved the maximum starting torque was 333 kN, and the adhesive coefficient was estimated at more than 0.35.
