SJ700D-055HFEF3 Variable Frequency Drive SJ700 5.5kW 3-ф/380

SJ700D-055HFEF3 — Hitachi SJ700 rated 5.5 kW, 3×380 V supply. Sensorless vector control holds over 200% torque at 0.3 Hz and 150% at 0 Hz, with 150% overload for 60 s — the frame for hard-start machinery around 5.5 kW.

Typical applications:

• small extruders and dosing units
• lab and test rigs
• compact hoists and winding units

Note: the SJ700D build — newer sensorless vector algorithm, drives both induction and PM/IPM motors; suited to a new install or an upgrade replacement. Modbus-RTU over RS-485 and built-in PID are standard; encoder (PG) vector and the braking module are options. Full range is in the Hitachi catalogue.

Hitachi SJ700 — heavy-industrial variable frequency drive, 0.7–160 kW, with sensorless vector control

Choose the SJ700 when you need high breakaway torque at low speed plus overload headroom: crushers, extruders, presses, hoists, conveyors with a hard start. Hitachi sensorless vector control holds over 200% torque at just 0.3 Hz and 150% torque at 0 Hz — an unusual figure for this class, and the reason the SJ700 ends up where a plain V/f drive simply won't move a loaded shaft. Overload is 150% for 60 s. In stock: 0.7–160 kW, 3×380 V supply.

SJ700B vs SJ700D — the difference

These are two hardware builds of one line at the same power. SJ700D is the newer build with an improved sensorless vector algorithm; it drives not only induction motors (IM) but also permanent-magnet synchronous motors (PM/IPM), and supports both heavy- and normal-duty operation (for fan/pump loads you can often size one frame down). SJ700B is the earlier build tuned for fan and pump applications with an automatic energy-saving function; it holds 150% torque at 0.5 Hz. They are compatible at the terminal, parameter and frame level. As a rule: for a PM motor or a new install — D; for a drop-in replacement in an existing fan/pump system — B is fine.

Where the SJ700 fits

• Hard start under load: crushers, mills, extruders, presses — where torque is needed from zero speed.
• Lifting and handling: cranes, hoists, conveyors — 150% at 0 Hz holds the load at start without a jerk.
• Large pumps and fans: trunk pumps, draft fans 30–160 kW — here the SJ700B with energy saving is the more common pick.

What sets the SJ700 apart

To be fair: Veichi and Delta are usually cheaper, and for a steady load (pump, fan) paying extra for an SJ700 makes little sense. Hitachi's strength is exactly its behaviour at low speed under shock torque. If the shaft has to break away under full load — the SJ700 wins there.

When the SJ700 is NOT the right pick

• Plain pump or fan control without a hard start — you'll overpay; see drives for pumps or for fans.
• Single-phase 220 V supply — the SJ700 is 3×380 V only; for a 220 V mains see single-phase drives.
• You need full closed-loop with an encoder out of the box — on the SJ700 that is an option (feedback board); for positioning check the vector-control drives.

Technical reference

• Control: V/f + sensorless vector (SLV); closed-loop vector with PG is an option.
• Maximum output frequency — 400 Hz; frequency accuracy — digital ±0.01%.
• Communication: Modbus-RTU over RS-485 (up to 115.2 kbps) as standard; built-in PID controller.
• Braking module is an option (for dynamic braking on crushers/hoists we add a braking resistor).

Our experience with the SJ700

The line mostly goes into heavy mechanics — where the customer already got burned by V/f drives that "can't pull" the start. The usual sizing question is "will there be enough shaft torque from zero" — for the SJ700 the answer is usually yes, but we advise costing the braking up front and adding a resistor on inertial machines. We keep both builds in stock on the common ratings; rare 132–160 kW frames are brought to order. Full model range is in the Hitachi catalogue and the general VFD section.