Three bolsterless two-axle bogies are used. The car body is supported by three bogies on air springs, two end bogies and one middle bogie. Traction efforts are transmitted from a Z-link connected to the center beam of the truck via the center pin.
The traction motor is a nose-suspension-type, and the driving gear is single-reduction. The journal bearing is elastically supported from the bogie frame in the lateral and longitudinal directions with rubber supports, which ensures bogie running stability. For tread brake equipment, a unit brake with automatic slack adjuster is used.
(4) Control
* Traction control
The notch command from the driver's console is simultaneously transmitted to both engine and exciter controllers and to six microprocessor units of traction converters. Engine speed changes to the value demanded by the command, and exciter current flows to perform suitable DC voltage. Next, the microprocessor unit of each traction converter adjusts slip frequency by monitoring the actual rotational speed and current, to control motor torque in accordance with the notch command.
The control unit also has a function for smooth re-adhesion when wheel slip. Wheel slip is detected by excessive acceleration of each wheel or excessive speed difference between wheels. Once slip is detected, the motor current is reduced immediately and current reduction is continued until the wheel speed returns to the correct value.
* Brake control
Brake control is performed by a combination of the electric command automatic air brake and the rheostatic brake.
The brake command amplifier controls both the rheostatic and air brakes, and the brake controller converts the electric command to air pressure. For optimum brake cooperation between the locomotive and various kinds of freight cars, jerk is monitored and controlled to vary braking performance with freight car type.
The air brake works additionally at high speeds, in coordination with the rheostatic brake, especially when the electric brake does not provide the required brake force.
2.3 Outline of Locomotive
Fig. 2.3 shows the outline of the DF200. The length of the locomotive is 19.6 m and the wheel base is 2.3 m. The axles weigh 16 tons each, and the total weight of the locomotive is 96 tons. Driver side entrance doors were eliminated to keep the maximum locomotive length within 20 m and make more space in the machine room.
Fig. 2.4 shows the machine layout inside the locomotive body. Both the electrical and mechanical configurations are symmetrical.
