Technical Papers

A Compact Specialist

One frequency converter, two designs

The compact frequency converter SD2B by SIEB & MEYER is especially suited to small CAD/CAM routing machines used, for example, in dental laboratories, for jewelry making or engraving works as well as producing advertising displays. Beside the classic design, the new SD2B plus design with additional functions and an IP20 housing is available now. Both designs stand out for their compact design and for keeping the motor heating as low as possible even at maximum power. This is beneficial especially for the sensitive bearings of the spindles but also for the machining quality.

Powerful, compact and reduced to the essential – this is the frequency converter SD2B by SIEB & MEYER. This device allows sensorless operation of synchronous and asynchronous motors with a speed of up to 120,000 rpm. "The 'classic' IP00 version of SD2B comes with the space-saving single board design that is quickly and easily built into the customer's construction. This is an important advantage for many users," Torsten Blankenburg, CTO at SIEB & MEYER AG, explains. "The reason: Low-voltage spindles are often installed in very compact machines which makes the available volume for built-in electronic components quite small."

Easy parameter setting and connection

Parameterizing the device is also very simple: By means of the software drivemaster2 the user can create parameter sets for asynchronous motors via V/f characteristic curve and for synchronous motors via basic data taken from the motor data sheet. As an option SIEB & MEYER offers a device version with USB interface for parameterization.

The devices of the series SD2B come with all interfaces required for the connection to a higher-ranking control, such as analog reference signals (+/-10 V), digital I/Os, RS232 and CAN bus. A low-voltage power supply unit with a wide range power input between 24 V and 80 V is used to provide the power supply. This permits optimal adjustment to the supply voltage of the machine and to the specific rated voltage of the motor. In many cases suitable voltages are available in the machine (e.g. 24 V, 48 V) which makes integrating the drive amplifier very easy and cost-efficient.

Further development of a classic: SD2B plus

SD2B plus is an advanced version of the existing one. This device permits control with sensors based on TTL encoders to make speed-controlled and torque-controlled motor operation possible; even from speed zero. Beside the TTL encoder inputs and outputs the new design provides five digital inputs and five digital outputs as well as a USB interface for easy parameterization as standard. "Our customers' feedback on SD2B was and still is very good," says Torsten Blankenburg. "Further discussions made it clear, though, that there is a demand for additional functions depending on the specific application."

In the field of optical system applications, for example, users requested to operate several high-speed motors with angular synchronism via master/slave connection. SD2B plus can do that; depending on the motor and encoder data, the device synchronizes motors up to speeds of 120,000 rpm within a few degrees accuracy. The robust speed control can also cope with high mass inertia ratios of up to 1:100 between motor and tool. All these advantages do not only apply to optical systems – as a pleasant side effect SD2B plus also supports sensor-controlled operation of machine tools.

More safety and an internal logic supply

The classic field of application for SD2B are machine tools for micro processing. Since safety technology is playing an increasingly important role even for the operation of such small machines, SD2B plus provides the safety function STO as standard. This function makes sure that the motor cannot generate torque-forming energy, which prevents unintentional startups. "This way, the machine manufacturer can implement the increasing demands towards machine safety at low costs," Torsten Blankenburg points out. "We are monitoring the development towards more operating safety of machines in many industry sectors. Therefore, we have integrated important safety functions into our devices."

In addition, SD2B plus comes with an internal logic supply, which makes the external 24 VDC supply redundant. Especially for multi-axis applications the DC supply voltage makes the use of one central power supply unit possible which reduces the wiring work and therefore the costs of the complete system.

An IP20 housing for switch cabinet installation

One difference to the established module is immediately apparent, since SD2B plus has an IP20 housing. "The open construction of SD2B is especially beneficial for machines with small installation spaces," Torsten Blankenburg explains. "Customers used to switch cabinet installations on the other hand, often want enclosed electronic components. With SD2B plus we can fulfill this demand." Even with the housing the device is still compact: Thanks to the reduced construction height of only 25 mm the required installation space for the frequency converter is still quite small.

Other dimensions of the housing are also possible: Generally, the series devices by SIEB & MEYER serve as a basic concept for customized solutions. SD2B plus, for example, allows modifications regarding performance and installation space. "The device provides a basis for all high-speed applications with low-voltage motors and we can adapt it to different performance or construction requirements," Torsten Blankenburg concludes.


SD2B in watch-making industry
The classic field of application for SD2B are machine tools for micro processing, for example in the watch-making industry (Copyright Fotolia: ©

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