Gives you more power to the ground for greater productivity.
Designed and manufactured by Caterpillar, the MT4400D AC is a 221 tonne (244 ton) AC electric drive truck that is single sourced from Caterpillar and supported through the Cat dealer network. The MT4400D power train works seamlessly with the 3516C HD engine to create a smooth ride and offers exceptional safety, serviceability and performance.
Modular Design for Excellent Serviceability
The modular design allows for easy removal and installation of components. The engine, traction alternator/generator, motors, inverter, grid, and final drives can be removed independently. The close coupled, dual bearing, traction alternator allows for easy mounting to the 3516C HD engine.
Superior Control Yields Excellent Operator Confidence
The Cat AC drive system gives you the best retarding, braking, and control in the industry. Class leading dynamic retarding coupled with blended braking, of the rear wet disc brakes and the front dry brakes, provide the operator with exceptional control and confidence.
High Voltage - Lower Heat
The Cat AC drive is a high voltage system (2,600 volts) that operates at relatively low current. The result is lower heat generation, smaller/lighter components, and longer component life.
The Cat AC Electric Drive in Propel
The 3516C HD diesel engine drives the close coupled traction alternator through an isolation coupler. The AC power is rectified to a nominal 2,600 volts to form the DC link. The DC link supplies power to the Inverter where IGBT’s convert the DC signal to 3-phase AC to drive the traction motors. Motor output drives the wheels through a Caterpillar double reduction ring output final drive.
Cat AC Electric Drive in Retard
During retarding the wheel motors become generators. Motor power is fed back through the DC link. The power is fed to the contactor and chopper circuits and then exhausted through the radial grid. A brushless AC fan blows air across the grid to dissipate the power and control retarding speed.
No shimming or radial alignment required with the close coupled, dual bearing alternator, resulting in decreased install time. The excitation system is brushless which has longer maintenance intervals than brush type systems.
The Inverter uses Mitsubishi Electric IGBT Phase Modules to control the rimpull, direction and speed of the truck. Mitsubishi Electric is the leader in IGBT technology.
Each traction motor is a 3-phase AC induction type. The high voltage, low current motor is mounted inside the rear axle box.
The radial design grid sits well back on the deck giving operators excellent visibility to the right side. The grid features the highest retarding power in the industry, better grid life, and is significantly quieter than box grids. The AC electric motor does not require any maintenance, which is a significant savings to the customer over DC motor systems.
Variable Hydraulic Blower
The hydraulic drive blower motor offers exceptional cooling, even in extreme environments. The variable hydraulic blower has the ability to provide the required cooling, even while the truck is at idle, compared to direct drive motors that are dependent on engine rpm. The variable blower is better at keeping critical components cool, and thus ensures long component life.
- Anti roll back prevents the machine from moving in a direction opposite the operator’s intent.
- The grid dry function dries the grid quickly in inclement weather.
- Traction Control System (TCS) electronically monitors individual wheel speed and adjusts the torque of each final drive to mitigate the hazard and keep the operator in control.
- Reverse Shift Inhibit ensures reverse propulsion is not applied when the truck is moving forward.
- Cat AC drive system is trolley capable.