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Trenchgate technology digs into drives power losses

01 February, 2000

Trenchgate technology digs into drives power losses

Hitachi claims to be the first drives-maker to use a new power semiconductor technology known as trenchgate, which it says can cut power stage losses by up to 30% compared to conventional planar IGBTs (insulated gate bipolar transistors) and achieve a 50% higher current density.

The company says that the technology also reduces the problem of electromagnetic interference. Hitachi is using the trenchgate technology in a new family of sensorless flux vector inverters that it says will deliver 150% torque at 0Hz, and more than 200% torque at 0.5Hz, without needing any feedback devices.

"We`re not trying to claim that we can stand still," says Steve Scales, joint managing director of Hitachi`s UK partner, HID, "but we have a true 0Hz, 150Hz torque". He sees this as being a particular attraction in applications such as lifts, hoists and conveyors, where it will deliver smooth, snatch-free starting and stopping.

Although other manufacturers are developing trenchgate systems, one potential drawback is the high short-circuit currents associated with the technology. Hitachi has tackled this by building a real-time current control circuit into its IGBT modules. Interference has been reduced by designing the modules for low stray inductance and parasitic capacitance.

The higher efficiency of the trenchgate IGBTs has allowed Hitachi to reduce the size of the new SJ300 drives by 30-50% compared to the previous J300 range. The drives also use new algorithms that combine slip frequency with real, rather than estimated, voltage values for control calculations.

One advantage of this is a claimed speed resolution of 0.5%. Initially, the SJ300 will cover single-phase ratings from 0.4-2.2kW, three-phase, 200V ratings from 0.4-22kW, and three-phase, 400V from 0.75-55kW. The 200V range will be extended up to 110kW and the 400V models to 400kW.

In addition to the SJ300, Hitachi has launched a family of voltage/frequency inverters targeting the building services sector as fan and pump drives for heating, air-conditioning and ventilation installations. The L300P also uses trenchgate technology, resulting in one of the smallest drives in its class.

The drives have been designed to be connected and run straight from the box. For ease of maintenance, components such as terminal rails and fans are pluggable. This includes the capacitors which can be replaced before they fail by checking a built-in indicator of the hours that the inverter has operated.

They L300P inverters incorporate automatic energy saving and PID controls. Three-phase 200V models span ratings from 11-22kW (soon to be extended to 110kW), while 400V models span the range 11-55kW (and soon up to 400kW).

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