The importance of drive train efficiency

As a manufacturer of IE2, IE3 and future IE4 motors, Bauer Gear Motor understands the value that a motor’s performance can place on running costs for an end user. However, the motor is just one piece of the puzzle.

Rather than breaking down the drivetrain into different sections and focussing on a single component, such as the motor, Bauer believes that a view should be taken of a single, ‘electro-mechanical’ package – one which must be fully integrated to achieve maximum performance. Despite the current focus on motor efficiency, the potential energy savings throughout the drivetrain can typically be distributed via the ZVEI model which is:

• 10% via improved efficiency of the motor,

• 30% via electronic speed regulation,

• 60% via optimisation of the mechanical system.

As the model shows, while it is motors that are currently grabbing the headlines for development, there is no point specifying the latest motor if the foundations are not already in order.

Using a speed control device to monitor and regulate a motor will straightaway make a significant improvement to any application that doesn’t require the motor to operate at full load at all times. Even when operating at full load, a motor with a variable speed drive installed will still be more efficient at start-up. The importance of speed control in real world efficiency is recognised by the introduction of Regulation 640/2009. This stipulates that from January 1st, 2015, any installation in Europe where an IE2 rated motor between 7.5 kW and 375 kW is specified, it must be installed with a variable frequency drive (VFD).

If it is the speed control device that unlocks the potential of a modern motor, then it is the mechanical components of a drive train that transmits the potential throughout the system. Within the electro-mechanical package, the mechanical components can be broken down into two sub-groups: gear technologies and drivetrain optimisation.

Specifying the most efficient gearbox allows for the transmission of a larger percentage of the motor’s power for its intended function. A well specified and efficient gearbox will avoid unnecessary oversizing, saving money from the outset, and reducing system losses in operation. It is these system losses that are a major factor in the EN50598 standard, which awards the new IES efficiency classes based on the efficiency of the complete power drive system.

Drivetrain optimisation is no less important than other considerations. Once each aspect of the drivetrain has been specified, it must then be integrated into the machine with as much efficiency as possible. 

That is not to say that steady improvements in motor efficiency are unimportant. The gains that have been made in the last decade are impressive, and beyond comparison to the relatively mature, and therefore slowly developing gear and drivetrain technology. So, while it is important that an efficient mechanical system is specified as a foundation, once that is in place, significant savings can be made by combining the latest electric motors with well integrated inverter drives.