With an outstanding reputation, direct drive motors are extremely popular and fit the bill for many applications created today. Known for their efficiency and reliability, with excellent power and performance statistics, direct drive motors are also much simpler, with fewer moving parts and lower maintenance requirements. As they use a frameless application, the need for framing, housing or bearing systems is reduced, allowing suppliers to integrate their motors into the application itself. This reduces the need for added interfacing and lowering the cost of ownership.
Efficiency is key to managing costs of electric motors. Depending on the application, up to 90% of the cost of ownership is in electricity consumption, so it makes sense to create the most optimised, efficient and cost-effective electric motor solution possible.
Often using a Permanent Magnet Synchronous Motor (PMSM), the initial costs of a direct drive motor will typically be higher than a lot of other alternatives. Cost factors will often be attributed to the amount of 'active materials' used in the motor. These materials - namely copper or aluminium for the wire, magnets and steel, are used to achieve the same power outage at lower speeds, as opposed to a high-speed motor with a transmission. There is always a sweet spot, however usually the active materials used will be higher in cost in a direct drive motor.
Direct drive solutions are typically designed around the specific criteria of an application. As there is no transmission to be adapted to the individual use case, the motor itself needs to be optimised for the specific case. This will invariably incur developmental costs. There are of course many off-the-shelf direct drive motors available, however the bigger the motor the less chance you have of finding something to suit your specific requirements.
The production costs will largely be dependent on the type and size of the motor required, and the quantity of active materials to be handled and used. Customised solutions can be designed in a way to be produced on standard machinery, which can reduce the investment in the production equipment required to produce the motors.
Direct drive motors can be highly integrated into the final product. Production can include other sub-systems or functions; therefore, the overall production cost of the product should be considered before commencing your project.
Componentry makes up a large part of the overall cost of many motor types. This includes but is not limited to the motor frame, transmission system and torque connection. Even though direct drive motors are more costly upfront, their lack of componentry helps to keep ongoing costs down. With fewer parts to wear out and potentially require replacement, the direct drive is superior to other motor types in this sense. Manufacturers can also minimise logistical and storage costs, along with other hidden operational costs, which all help to keep the total system cost at a competitive level.
The cost of commodities worldwide is volatile and has never been more so since the COVID-19 global pandemic began. Active materials used in direct drive motor production such as copper or aluminium wire, electrical steel, along with Neodymium and ferrite magnets are continually sourced and supplied to ensure ongoing motor production. Costlier components such as Neodymium magnets and copper are becoming more in demand as electrification increases in many industries. The option of cheaper, more sustainable materials is worth looking into however the use of these materials invariably impacts performance in terms of lower power density or increased need for cooling.
Many factors will contribute to the cost of a direct drive motor solution. When looking into a solution, the initial costs are likely to be higher than other alternatives, and we have touched on some of the contributors in this article. A superior motor choice, a direct drive makes a lot of sense for many applications, however it is important to weigh up all the initial and ongoing costs of this or any other motor choice before reaching the decision-making process.