Frequency converters

Good start for SD4x frequency converters

Good start for SD4x frequency converters

Good start for SD4x frequency converters

Good start for SD4x frequency converters

Good start for SD4x frequency converters

Good start for SD4x frequency converters

The development of the new SD4x series of frequency converters for high-speed applications progresses with great strides: In the course of the year 2022, the SD4S series by Sieb & Meyer AG will grow to a total of nine sizes, which cover and even extend the current power range of the SD2S series. In addition, SD2M models, which are equipped with state-of-the-art power electronics, will be transformed to the powerful SD4x platform.

"In the long run, the SD4x devices will replace the frequency converters of the series SD2x," explained Ralph Sawallisch, key account manager drive technology at Sieb & Meyer AG. "In this regard, we are well on the way: the SD4x product family grows steadily." Until recently, the focus was still on field testing of the new SD4x development platform. The first SD4S device variant was developed foremost to close a gap in the existing product line of frequency converters regarding the lower power ranges: it is a switch cabinet variant of SD4S with 800 W / 1.6 kVA. At the end of the second quarter of 2021, another construction size with 1,600 W / 3.2 kVA was available. These SD4S variants make an optimal basis for the operation of high-speed spindles and motors in the power range from a few hundred watts up to 1.6 kW. "Both device variants are already working successfully in customer installations," said Ralph Sawallisch. "Testing in different applications proves that we have developed a stable system for universal use."

Series start for SD4S and SD4M

The functionally tested successor products for the SD2S and SD2M series are ready for the market. Over the first half of the year 2022, SD4S will be available in five construction sizes in the 230 V class; over the second half of the year, four additional construction sizes in the 400 V class will be launched. Together these devices cover the current power range (1.4...55 kVA) of the SD2S series and even extend it downwards and upwards (0.8...66 kVA).

In addition, the SD2M series becomes the SD4M series. In 2021 Sieb & Meyer launched a new SD2M construction size with a higher output power and output current of 470 kVA / 800 Arms (at 400 V) that allows for powerful system solutions in the sector of turbo blowers and turbo compressors. "This device comes with state-of-the-art power electronics," explained Ralph Sawallisch. "We have prepared everything so that this device can be transferred as a new logic variant into SD4M. This makes the changeover feasible relatively quickly."

Customers mainly benefit from the improvements to the control loop and the Ethernet-based bus systems. Existing customers can of course continue to use SD2M – for new projects, though, switching to SD4M is quite easy. "There is not much to be adapted on the power side," said Ralph Sawallisch. "On the logic side, customers only need to use a slightly different connector and consider a few minor differences." By the way, switching from the SD2x series to the SD4x series is quite easy, since the parameters are simply transferred from the SD2x devices.

Ready for the future – in numerous applications

"With regard to functions and control technology the SD4x series provides even higher gains compared with the predecessor series SD2x. One example is the expansion of the speed range of the sensorless vector control up to 240,000 rpm," said Ralph Sawallisch. "We have already gathered initial positive practical experience with sensorless synchronous motors in the speed range up to 180,000 rpm (3,000 Hz)." For comparison: sensorless operation of the predecessor series SD2x was limited to 120,000 rpm (2,000 Hz). Moreover, Sieb & Meyer has added a vector control for asynchronous motors with encoder feedback to the existing drive functions and thus extended the application range of the SD4x series even further.

With the multiprotocol chip, which is used for the commercially established Ethernet-based interfaces, as well as useful additional functions like a real time clock, the SD4x devices are well prepared for the future. Although the devices come with future-oriented, purely digital interfaces for communication, analog interfaces are still available via option boards to connect analog speed sensors, e.g. resolver and sin/cos 1Vpp.

Better performance and new control functions

The key feature of the SD4x product family is the significantly increased processor performance: The new 32-bit processor is up to five times faster, thus allowing a higher resolution and more precise calculations. Sieb & Meyer has also switched from a fixed-point to a floating-point arithmetic, which allows for a more flexible software design. All in all, the new processor system enables users to perform more complex tasks faster. On the hardware side, a new FPGA makes 1.8 times faster calculations possible, which allows executing more complex control tasks. For customers, this translates into a considerable performance increase. Higher switching frequencies and an enhanced control performance at even higher speeds lead to an optimized overall process.

Thanks to an integrated position controller, SD4x devices are able to perform high-precision positioning tasks on their own. In addition, the new devices support higher PWM switching frequencies of 24 and 32 kHz. For an even finer modulation of the sine-wave signal, a commutation angle control for 32, 48 and 64 kHz is integrated. The result is an almost optimum sine with nearly no harmonic currents. Moreover, the power loss caused by the PWM can be reduced to a small fraction. Dynamic servo applications also benefit from the improvements to the control loop: design-related influences of the motor like cogging are minimized – this was proven in practice in applications of reference customers.

Besides, Sieb & Meyer uses the available processor performance for new control functions. As a result, SD4x devices can optimally operate synchronous motors with magnets embedded in the rotor, so-called interior permanent magnet motors (IPM). The reluctance torque generated by these motors is optimized in real-time depending on the operating point. "Other systems generally use a static optimization on a fix operating point," explained Ralph Sawallisch. "That way, it is not possible to use the full capacity of the motors for broader working areas."

Simple parameterization and diagnostics

Another highlight is the new software Drivemaster4. It is the control center for the frequency converter family allowing initial parameterization and initial operation as well as diagnosis. The integrated software tool Motor Analyzer enables meaningful simulations of the frequency converter operation. This allows for an FFT analysis of the simulated output current. With the figures for the total harmonic distortion (THD) of the motor curent (THDi) and the motor voltage (THDv), expert users are able to estimate the motor heating more accurately. Based on these data, users can also create a digital system twin, which enables a considerable risk minimization and cost reduction during the development process.

In addition, Sieb & Meyer continuously develops the software Drivemaster4 for international customers. Beside the German and English user interface, the software will soon be available in Chinese. Japanese, Korean and French will follow.

"We look forward to the extensive series launch of SD4S and SD4M," concluded Ralph Sawallisch. "Then, even more customers will benefit from the key advantages of the SD4x product family: optimized performance, higher speeds and low motor heating without additional sine-wave filter." Behind the scenes the development continues. The next development stages focus on functional extensions. In addition, Sieb & Meyer will increase the number of customized solutions based on the SD4x platform  – it opens up completely new opportunities after all.

By Torsten Blankenburg, CTO, Sieb & Meyer AG

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