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Hannover Messe Hall 12, Stand D73

Hedgehog Electric presents the completely redesigned digital soft starter ISA-SL3, which will replace the ISA-DS series undergone several facelifts in the last 13 years. In addition to insights from the medium-voltage sector, the experience of several customer-specific development projects has been incorporated into the development. The inductive galvanic isolation of the power unit from the control unit, which is used for the first time, renders the ISA-SL3 insensitive to harmonic-charged power supply networks and is therefore ideally equipped for future requirements and events.


In particular, new components have been implemented and tested in recent years, which were then transferred to the ISA-SL3 product line with sufficient field experience. From a technical point of view, the basic technology of soft starters has not changed in recent years. New components are more likely to optimize the size and performance of the devices. From a technical point of view, there is a tendency for more complex solutions.

This tendency is primarily due to the approach of the soft starters to the frequency converters, while the first devices were rather compared with a star / delta connection. Thus, he gave two basic factors that have significantly determined the design and performance of the new product series: experience and problems with the current ISA-DS series and experiences and wishes of our customers and users.

Errors should be avoided

Especially the first point "error avoidance" has led to a fundamental new development of the soft starter. Due to the ever increasing load of the supply networks by harmonics, it has come in some applications to equipment failures. In combination with an IT network, as found on ships and in the chemical industry, an accumulation of failures occurred. The problem with these errors is the temporary load on the networks due to harmonics, depending on the load and consumers connected. Especially these temporary, sometimes only seconds-lasting conditions make troubleshooting almost impossible. However, the effect of harmonics is the same for all causes. Thus, certain resonance frequencies are hit by internal circuits and damaged by the high current flow. Based on these findings, a fundamental change was made in the design of soft starters.

In the ISA-SL3 series, a continuous galvanic isolation of the power level from the control plane has been implemented. In addition to optocouplers for the energy-free signals an inductive technology was used, which allows transmission of the ignition signals. The combination of integrated galvanic isolation combined with inductive transmission technology represents a solution in which disturbances due to a harmonic load network can be ruled out. This technology is currently used worldwide exclusively in the ISA-SL3 product line. Based on service evaluations in recent years, the development department expects a reduction in returns of significantly more than 50%.

Individual product design

The application- and customer-oriented product design was the second decisive factor in the development. For better needs analysis, the customers were divided into four groups: switchgear manufacturers and system integrators, end customers, planning offices, as well as brand label partners and export customers. The same applies to all customers, the reliability, ease of use and cost optimization on the wish list.

As mentioned at the beginning, reliability was the highest priority. The use of already proven components and the novel galvanic isolation have significantly increased the reliability compared to the predecessor model. For ease of use of the soft starter was deliberately set to internationally accepted standards. Thus, the devices have a standard USB interface which together with a Windows-based software allows the parameterization and monitoring of the soft starters. Of course, the parameters can be saved, the data sent by e-mail and played back again. The subject of cost optimization was not only reduced to the factor cheap, but also considered holistically. So there is actually a cheaper variant of the soft starter, which is in this case to the control of the motors via only two switched phases.

In many standard applications, this technology has already established itself on the market and will be available for the first time in up to 3 kW through the ISA-SL600 series. Another important factor in cost optimization is the reduction of storage and spare parts costs. In this point, a customer-friendly configuration of the devices was consistently taken into account. Thus, the actual soft starter represents only the basic variant. Any options that may be required can be retrofitted by the customer later in Plug and Play mode. This means, for example, that a Profibus card is plugged into the free slot and the soft starter automatically recognizes and integrates this option card.

In addition to the general requirements for a customer-friendly product, there are of course customer-specific requirements. The switchgear manufacturer or system integrator would like to have a standard supplier for all softstarter applications. In the globalized world, this means a wide range of voltages / currents and network frequencies. With the voltage range from 230 to 690 V and 8 A to 1100 A, the ISA-SL3 product line covers more than 90% of market requirements. For larger outputs and voltages in-house can be used on other product. Furthermore, a short delivery time is at the top of the wish list. Again, the modular design helps to deliver the appropriate device from stock.

The end customer, on the other hand, thinks more in terms of application or application. The electrician wants optimal start-up performance for his system. Here the ISA-SL3 offers different pump curves, torque curves, protection functions and stop curves. Minimizing downtime is an important goal, especially in the industrial environment. In the case of an error, it is superficial first of all to have a quick repair. The complete restoration of the plant can then be carried out at the next scheduled shutdown. This is exactly where a new feature of the ISA-SL3 comes in. In the event of a fault in a power phase (thyristor fault), this phase can be bridged externally by a cable and the soft starter can then be put back into operation directly without further work. The device recognizes the bridge automatically and then continues working in 2 phase mode.

Optimization potential for the planning effort

At the planning offices, the manufacturer sees a great potential for optimization in terms of planning effort. Thus, the entire application is covered with only one product series, which also always has the same control unit. As a result, the same connection modules can always be used. Furthermore, the selection of the respective soft starter is facilitated if the device has the required approval in the project. As with the ISA-DS series, the ISA-SL has all current international approvals, so that not only the technical parameters but also the legal side is considered.

As the largest customer area, the brand label partners and export customers were considered. In addition to many requirements already mentioned above, product customization is in the foreground here. The use of a printed circuit board-mounted control and display unit has virtually no limits on the design of the plastic cover. Thus, a potential Brandlabel partner can design the device completely independently, without generating high investment costs. In addition, the partner can adapt and change the complete parameter naming according to his wishes via a simple Excel-based tool. This not only allows the maintenance of any language imaginable, but also extends to personalized error messages such as "Pump 23 Overtemperature bearings".

No special customer group can be assigned and thus a kind of special features round off the possibilities of the ISA-SL3 product series. For certain applications, soft starters are connected in the so-called root 3 circuit. As a result, the starter nominal current is reduced by the factor "root 3", so that as a rule the next smaller product can be used. However, in terms of overall balance, this cost saving is usually used up again due to the extra effort of the 6 motor cables. For the first time, the root 3 feature also features automatic detection of incorrect wiring, which adds real value to users.

In the low voltage range also rather a rare application is the multi motor control. Here, with the help of only one soft starter several motors are started in a cascade one after the other and bridged by an external circuit. Again, the same applies as with the root 3 circuit that the additional cost of installation eliminates the price savings on the soft starter again.

For one or the other customer, the event memory of the last 99 events with the respective time stamp is of interest, as well as an optional motor insulation measurement and the front-end possible firmware update via the bootloader.
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