19 March 2008
The SJ700 is an off-the-shelf unit with integral easy sequence programmable functionality (EzSQ) as standard. It is compact in size, designed to help users and system builders reduce control panel size. It also incorporates power switching technology, claimed to reduce dVdT, with the IGBT (insulated gate bipolar transistor) stack at the heart of the drive. High dVdT is associated to motor insulation breakdown by the increased terminal voltage of motors when used with AC drives.Stuart Harvey of Silverteam said large drives are often used for many years and can look dated when replaced, adding: ‘The SJ700 resets the benchmark for small and medium sized drives, offering multipoint positioning and near servo performance from a standard induction motor’. He continued: ‘The 160kW-400kW SJ700 makes similar performance available right through the power range.’The SJ700 is a sensorless vector drive, with 150 per cent torque at zero speed and near total immunity to motor constants problems. An optional feedback card can be used to close the vector loop.Harvey said: ‘The built-in EzSQ functionality provides a very powerful controller that negates the need for an external unit such as a PLC in even the most demanding of applications.‘Its communication with both the external system and the drive’s internal circuitry is naturally very fast and very secure. This enhances operational performance all round.’Silverteam said the large drives should set new performance standards in water pumps, fans, hoists, lifts and many other applications.‘With lifts, for example, we can offer very smooth floor transitions with adjustable S ramps and brake release confirmation signals, while the superior torque and speed control make it particularly suited in hoist applications like cranes or theatre flying systems,’ Harvey said.‘There are savings because you don’t have to buy a separate PLC, panel space savings, installation and commissioning time savings and an increase in reliability.’Hitachi has designed the drive for a working life of at least 10 years. Harvey said: ‘Every detail has been looked at to design out possible failure modes. The patented switching is just one example of this.‘We tested all the leading drives with many different makes of motor. Voltage spikes leading to insulation breakdown was always a potential problem particularly with cable runs over 50m, so we gave the designers the targets of reducing problems to negligible levels and for the drives to be usable with cables over 100m long without line reactors. To achieve this they could not refine existing techniques, so they had to develop next generation technologies.’ The SJ700 also includes brake transistors on sizes up to 22kW, integral EMI/RFI filters, comms options, customisable display panel, intelligent energy saving, active frequency matching for restarting and flying load catching, regenerative braking under E-stop conditions and RoHS compliance.
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