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`Five times faster` inverter avoids nuisance trips

10 May, 2007

On its stand at the recent Hannover Fair, Hitachi unveiled two new drives families – its first all-new ranges for several years. The company’s new flagship range, the SJ700, is five times faster than the SJ300, which it will replace. The new range will eventually span ratings from 0.75–400kW, marking Hitachi’s first entry into the market above 132kW for more than a decade.

Hitachi SJ700

Although the SJ700 (shown above) looks similar to the SJ300 and uses the same programming, it has been redesigned completely. For the first time, it has built-in filters as standard. Other features include:
º  200% starting torque at 0.3Hz;
º  a combination of over-current and over-voltage suppression which avoids nuisance trips during acceleration and deceleration;
º  built-in braking up to 22kW;
º  a new power switching algorithm said to halve dV/dt effects, thus helping to protect motor windings;
º  a stabilisation function that avoids judders as a load slows down; and
º  the ability to have cable runs of up to 100m without needing filters.

A new Windows package with a "PLC front-end" can be used to program the SJ700 using a Basic-like high-level language. This can be used for position control (with an encoder) and allows complex logic sequences to be downloaded to the inverter, avoiding the need for external PLCs or relays. It can also be used, for example, to provide automatic speed control based on the load, for applications such as cranes.

The SJ700 is due to go on sale in Europe soon at a similar price to the SJ300.

Hitachi X200

Hitachi’s second new range, the X200 (shown above), is a compact inverter aimed at OEMs. It costs less than the present L200 range, but offers more functions and has built-in filters and a safe-stop function. It provides "enhanced" V/f control and incorporates similar trip avoidance functions to the SJ700. It will span ratings from 0.2–7.5kW.

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