200 and 250 kW Electric Motors: Supply, Starting, Handling and Spares Planning

A 4-pole, 250 kW IE3 motor on a 400 V supply draws about 418 A at rated load. Started direct on line, that climbs to roughly 3000 A. The motor weighs over a tonne and delivers around 1600 Nm at the shaft. At 200 and 250 kW, choosing a motor stops being a product decision and becomes a small project: if the transformer, starter, cables, foundation, lifting and spares are not planned alongside the motor, even the right motor will cause trouble on site.

Reading the catalogue line

In the HEM Motor IE3 catalogue the two ratings sit in these frames (currents at 400 V):

• 2-pole: 200 kW IE3-315L2-2, 2980 rpm, about 331 A; 250 kW IE3-355M-2, 2982 rpm, about 414 A.
• 4-pole: 200 kW IE3-315L2-4, 1490 rpm, about 334 A, 1282 Nm; 250 kW IE3-355M-4, 1490 rpm, about 418 A, 1602 Nm.
• 6-pole: 200 kW IE3-355M2-6, 990 rpm, about 346 A; 250 kW IE3-355L-6, 990 rpm, about 433 A.

For the 4-pole versions, IE3 efficiency is 96.0% and power factor 0.90 at both ratings. Starting current is about 7.1 times rated current, starting torque about twice rated torque and breakdown torque about 2.2 times. On the 2-pole 250 kW motor the starting torque ratio drops to 1.6, so if it is meant for a compressor that starts loaded or a high-inertia fan, check the load's starting torque separately.

Efficiency class depends on the market

Under the EU Ecodesign regulation (EU 2019/1781), 2-, 4- and 6-pole motors from 75 to 200 kW have had to meet IE4 since July 2023, while IE3 remains the minimum above 200 kW. A machine exported to the EU can therefore face different rules for a 200 kW and a 250 kW motor. Clarify the regulation at the installation site before asking for a quote. HEM Motor offers IE3, IE4 and IE5 in the same frame system at these ratings; for 4-pole motors the IE4 limit is 96.7% and IE5 97.4%. The power bands are covered in the IE3 and IE4 efficiency mandate. Small percentages add up at this size: a 250 kW motor running 7000 hours a year at full load saves roughly 13,000 kWh annually from the 0.7-point gap between IE3 and IE4.

Supply and starting method

Direct-on-line starting at 200–250 kW only works with a strong transformer and a light starting load. Most plants choose between:

• Star-delta: cuts starting current and torque to about one third, taking a 250 kW 4-pole motor from about 3000 A to around 1000 A. The motor must run in delta at 400 V, i.e. have a 400/690 V winding. Because torque also falls to a third, it suits pumps and fans started unloaded or against a closed valve, not loaded conveyors.
• Soft starter: limits current to a few times rated value and ramps the start; common on pumps and fans. For loaded starts, set the current limit high enough to provide the torque the load needs.
• Autotransformer: preserves more torque than star-delta on long, heavy starts, with tap selection and short-time duty to consider. See autotransformer starting.
• Variable frequency drive: keeps starting current near rated current and is the natural choice if the process needs speed control.

Whatever the method, know the transformer rating and fault level before deciding, and check whether sensitive loads on the same transformer will suffer from the voltage dip at start.

400 V or 690 V?

A 418 A feeder at 400 V means parallel cables and heavy switchgear. If the plant has, or is building, a 690 V distribution, the same motor connected in star at 690 V runs at about 240 A, and cable, busbar and drive costs fall accordingly. This is usually a site-wide decision rather than a single-motor one. Terminal and starting implications are explained in 690 V induction motor selection.

Running on a drive: bearings and cooling

Large motors fed from a frequency converter can develop shaft voltage that discharges through the bearings and leaves fluting marks on the raceways. Insulated bearings or a shaft grounding brush may be needed at these frame sizes, so state inverter duty clearly in the order. Long motor cables call for a dv/dt or sine filter. If the motor will spend long periods well below rated speed, ask whether a separate fan is needed, because the shaft-mounted fan loses airflow at low speed. For cooling arrangements, see IC411 and IC416 cooling.

Handling, foundation and commissioning

The catalogue lists the 2-pole 200 kW motor at about 1194 kg and the 250 kW at about 1685 kg; 4- and 6-pole units are in the same range. In practice:

• Plan crane, forklift or hoist access to the final position, and check door and corridor sizes.
• The foundation must be stiff enough for the motor's weight and the reaction torque at start. A flexible base produces high vibration readings that have nothing to do with the motor.
• Align the coupling with a laser tool and recheck once the machine is warm.
• Measure insulation resistance before first start and check rotation with the coupling disconnected.

Spares and supply planning

A failure at this size normally stops the whole line. For critical drives, settle three questions early: will a spare be kept on site, can one spare cover several motors of the same frame, and how will the line run while a failed motor is repaired? Standardising power and pole count across motors is the most effective way to reduce the number of spares. A spare kept in storage also needs protecting against moisture and bearing damage.

Conclusion

Choosing a 200 or 250 kW motor starts with the catalogue line and ends with the right efficiency class for the market, a voltage and starting method that suit the supply, the extra requirements of drive operation and the physical installation. These ratings belong to HEM Motor's cast iron electric motors range. Send a request with transformer rating, starting method and mounting to our technical team and we will review a suitable model and stock status together.

Frequently Asked Questions

What transformer size does a 250 kW motor need?

No single figure is right: transformer rating, fault level, starting method and other loads on the same transformer all count. Because direct-on-line starting current exceeds seven times rated current, most plants use star-delta, a soft starter or a drive.

Can a 200 kW motor on a machine for the EU be IE3?

Under EU 2019/1781, 2-, 4- and 6-pole motors from 75 to 200 kW have required IE4 since July 2023. For machines going to the EU, plan on IE4 for a 200 kW motor and check whether any exemption applies to the operating conditions.

Do large motors always need insulated bearings?

Not usually when they run directly from the mains. On large frames fed by a frequency converter, the risk of bearing currents rises and insulated bearings or shaft grounding may be required, which should be specified at the ordering stage.

Is a 2-pole 250 kW motor suitable for loaded starts?

The catalogue gives its starting torque as about 1.6 times rated torque. If the load needs more at start-up, or the run-up is long, check the starting method and motor choice against the load curve.