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Smaller than an AC motor, and more cost-effective than a servo

Smaller than an AC motor, and more cost-effective than a servo

Stober has defined a new category of electric motor which is says mixes the properties of a synchronous servo motor, asynchronous motors and switch reluctance motors. The new interior permanent magnet synchronous machine that enable the creation of innovative machine designs.

Introduced to the world at the SPS/IPC/Drives fair in November, the LeanMotor from Stober is a new concept in motor design that bridges the gap between servo motors and asynchronous motors. The LeanMotor is a highly efficient and compact electric drive that is significantly lighter and smaller than an asynchronous drive. And with the same output as a more expensive servo drive, the LeanMotor is a robust and cost effective option for those looking for higher performance at a lower cost.

More rugged than a synchronous motor and delivering better performance than an asynchronous motor, it exceeds the IE4 efficiency level in its respective performance group. Its fan-less construction, with integral holding brake, means it is smaller than comparable drives and with a single power connection, very easy to fit.

What’s more, its robust construction means that the LeanMotor can be used for dynamic automation tasks in harsh production environments. It also allows for variable regulation of speed and torque from a standstill to maximum speed with full torque control, without the need for positional sensor elements. And being small and light, engineers can design more compact machines, while users benefit from lower energy consumption and long service life.

Specification of the LeanMotor also means that the need to use heavier and larger asynchronous motors is eliminated, with the smaller size and lower weight combination providing around 30% improvement in cost-efficiency. Additionally, it can regulate more dynamically and efficiently when compared to an asynchronous motor with incremental encoder thanks to its greatly reduced flywheel mass. Defined as an interior permanent magnet synchronous machine (IPMSM), it features a design where the magnets are embedded within the rotor, enabling the controller to take advantage of the anisotropic behaviour of the motor inductance. The smart design of the rotor optimises the magnetic path as well as using the reluctance properties to realise maximum torque. And with less permanent magnet material used, more torque is available.

With appropriate drive controller algorithms, this design enables sensorless motion control. These algorithms have been implemented within Stober’s SC6 and SI6 drive controllers, enabling variable regulation of speed and torque, from standstill to maximum speed, without position sensors. In the speed range from 0-1000rpm, a high frequency injection technique is used to determine the rotor position. Above 1000rpm, the position is determined by using an EMF-based method. Speed and positional accuracy is ±1°. Stober says the performance of the LeanMotor with its SC6/SI6 controllers is comparable to an asynchronous motor with a 1024 line incremental encoder.

The increased efficiency of the design is another key feature. Efficiency exceeds IE4, and within some power bands the efficiency even exceeds IE5.

Benefits for engineers and designers are that smaller drives can be designed, commissioning and maintenance costs are reduced and that this new drive can integrated with a wide range of Stober gear units and accessories, such as a rugged spring-loaded holding brake. This provides high braking performance throughout the entire service life.

The motor is protected to IP56 as standard, with IP66 as an option, but the design also suites it to use in challenging application areas. It is well-suited to automation applications that are exposed to high vibrations and oscillations. In applications that might currently use or consider an asynchronous motor, the LeanMotor will be significantly lighter and smaller for the same output. It offers efficiency up to 96%, and higher acceleration ability than a synchronous motor. You’ll also benefit from dynamic regulation of speed and torque at lower speeds, without an encoder.

If you would typically have considered a synchronous servo motor for a given application, Stober says the LeanMotor offers a cost-effective and rugged alternative. It also addresses the needs of applications in harsh production environments or where there are high levels of vibration or oscillation. This ruggedness comes by virtue of the fact that there are no electronics in the motor. And motor connection requires only a standard power cable.

Applications include all types of automation and precision positioning tasks. Bridging the gap between an AC motor and a servo motor, the LeanMotor brings IE5 level efficiency, enables you to design more compact machines, delivers a long service life, requires only a standard power cable connection, and defines a new motor class that lets you tackle dynamic automation tasks in harsh production environments.

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