By Sam Meeker, Market Professional – Dozers, Caterpillar Inc.
Still getting used to the idea of powershift automatic shifting on your heavy equipment? Now, on some machines, you’ve got another choice: electric drive. What exactly is different? Why would you pick one option versus the other? And what makes either better than a traditional powershift transmission? You’re not the only one asking these questions. We’ve got some answers.
Electric drive, defined
Here’s the simplest way to explain electric drive:
- An engine drives a generator (instead of a torque converter) that converts mechanical power into electricity.
- An electric motor (instead of a transmission) powers the final drives.
- A power inverter (connected to both the generator and motor) controls the flow of electricity between the two components.
The electric motor can operate at all ground speeds, ensuring the machine is always operating at the most efficient point possible. The drivetrain can vary torque delivery to the final drives with minimal change to engine speed. Both of these factors help reduce fuel consumption and can extend engine life. Another benefit: Electric drive has 90% fewer moving parts than a traditional powershift transmission for simpler, less expensive maintenance.
Comparing your options
The easiest way to see the differences is to look at one machine — the Cat D6 Dozer — that’s available with either electric drive or auto shift, then compare it to the previous powershift model (the D6T).
The electric drive next generation Cat D6 XE requires a bit more investment up front, but fuel savings can reach up to 35% versus the three-speed D6T. There are no gears to shift — instead, power to the ground is continuously optimized for forward momentum throughout the push. You also get faster cycle times, thanks to a combination of constant power to the ground, continuous push and greater maneuverability. Work the D6 XE hard, and you could recoup the cost difference in two years or less.
With a four-speed, fully automatic transmission, the D6 is priced lower than the XE model but still delivers fuel savings — up to 20% over the D6T. Fully automatic shifting with an added transmission gear reduces the momentary hesitation felt when a traditional machine shifts, so you maintain more momentum and drawbar power throughout the entire push. And, because auto shift works up and down the entire working range, power to the ground and fuel consumption are optimized for a greater percentage of the time.
Making the right choice
Choosing between electric drive and auto shift comes down to your application and goals. Both are easy to operate — just set the ground speed and let the dozer automatically optimize based on load for the greatest productivity and fuel efficiency. That said, if your job requires the highest levels of both productivity AND fuel efficiency, it pays to consider the added benefits of electric drive.
Want to learn more about the differences and benefits? Take a closer look at the D6 XE and D6.