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Compact inverters offer safety as standard

18 April, 2011

Mitsubishi has announced a compact inverter that, it claims, takes integrated safety to the next level. The FR-E700SC-EC inverter – which succeeds the earlier FR-E700 – includes a Safe Torque Off (STO) function and a safety terminal block.

The inverter, which is said to be one of the smallest in its class, can operate in vector, sensorless vector, V/f or optimum excitation control modes. It spans two ranges: 0.1–2.2kW, single-phase; and 0.4–15kW, three-phase. An extended vector control algorithm allows the inverter to achieve torques of 150% at 1Hz, even with wide variations in motor characteristics.

The STO function prevents the inverter from restarting automatically after a stop, thus protecting personnel and machinery. It disables the drive signal to the motor without turning off the power to the inverter, thus preventing hazardous motion but allowing quicker restarts after stoppages. It also saves panel space and costs by avoiding the need for isolating contactors.

By changing from screw terminals to advanced spring clamps in the removable terminal block, wiring has been speeded up and user protection increased.

After a power failure, regenerative energy can be used to perform controlled deceleration of the motor, thus preventing uncontrolled run-down and possible machine damage.

Other features include: a USB port that can link to a PC for rapid configuration, monitoring and maintenance; a one-touch digital dial control with a LED display for rapid access to key parameters; and improved power usage at low speeds.

Plug-in option cards can connect the FR-E700SC to CC-Link, Ethernet, Profibus, DeviceNet or LonWorks. Various I/O modules are also available, providing RS-485 interfaces, pulse-train outputs, and high-resolution analogue I/O.

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