Ordering a 315 kW Electric Motor: Technical and Logistical Details to Check

Ordering a 315 kW motor differs from buying a motor of smaller power in two respects. First, the motor's electrical and mechanical details depend on other decisions, from the plant's transformer to its base; a wrong assumption turns into a problem that is hard to fix once it is noticed after the motor arrives. Second, getting the motor to site and into position calls for separate planning. In this article, based on HEM Motor's 315 kW models, we have gathered the technical and logistical details to be settled before ordering into a checklist.

The 315 kW models and a notable detail in their codes

HEM Motor's three-phase product range is 0.25–355 kW; 315 kW is one of the top steps of this range. At 315 kW the options have cast iron frames and there are three of them: 1,000, 1,500 and 3,000 rpm. Protection IP55, insulation class F, supply 400/690 V (Δ/Y), 50 Hz; service factor 1.15.

All three models are in the 355L frame. There is an important detail here: the code 355L-4 is used not only at 315 kW but also for the 355 kW, 1,500 rpm model. Similarly, the code 355L-2 appears on both the 315 kW and the 355 kW 3,000 rpm models, and 355L-6 on both the 250 kW and the 315 kW 1,000 rpm models. For this reason, writing only the model code in an order is not enough; power, speed and code should be written together, and the quotation should be checked to show all three correctly. Since the rated speed, current and torque of the 1,000 rpm model are not in the site's records, confirm them from the 2026 catalogue or during quotation.

What to settle on the electrical side

Supply voltage and connection

A motor rated 400/690 V (Δ/Y) is connected in delta on a 400 V network and in star on a 690 V network. At 315 kW on a 400 V supply, the rated current is above 500 A; this current directly determines the cable cross-section, the number of parallel cables and the switchgear. Some plants prefer 690 V distribution at this power. State clearly in the order which voltage will supply the motor and the connection; although the same motor suits both networks, cabling and protection decisions change accordingly.

Starting and transformer

At this size, direct-on-line starting strains the limits allowed by the transformer and the network in most plants. Star-delta, soft starters and frequency inverters are common options; which is suitable is assessed together with the starting load of the driven machine and the transformer rating. If a frequency inverter is preferred: our three-phase series are suitable for speed control with a drive. If full torque is to be drawn at low speed for long periods, an additional (external) fan may be needed; when the cable between the drive and the motor is long, a dv/dt or sine filter is considered. For details, see the question on use with an inverter.

Protection and order options

• Winding temperature sensors: PTC or PT100 winding sensors are options chosen at the order stage. State whether your panel has a relay or input to read them.
• Anti-condensation heater: If the motor will stand idle for long periods or wait in a humid environment, an anti-condensation heater can also be requested with the order.
• Terminal box and cable entry: The number of cables, their cross-section and the direction they come from should be stated; whether large parallel cables will enter the box comfortably is discussed in advance.

What to settle on the mechanical side

• Mounting arrangement: Arrangements such as foot-mounted (B3) or foot-and-flange are offered according to the frame; the flange size is confirmed with the order. Which arrangements are possible is summarised in the question on mounting arrangements.
• Base and alignment: Shaft height, foot hole spacing and shaft end dimensions are in the 2D technical drawings. If the motor replaces an existing one, the old motor's frame size and the values measured on site should be compared.
• Transmission: Coupling, belt or gearbox? The rated torque is 2,019 Nm for the 1,500 rpm model and 1,009 Nm for the 3,000 rpm model; transmission elements are selected for this torque. In a belt drive, the radial load should be stated separately.
• Cooling air: There must be enough clearance on the motor's fan side, and hot air must not be drawn back in. In an enclosed motor room, the ventilation capacity is also checked.

Interpreting the service factor of 1.15 correctly

The 315 kW models have a service factor of 1.15: the motor is designed with a margin that can carry roughly 15% more than the power on the nameplate. This reserve is a safety margin for load fluctuations, higher ambient temperature or calculation uncertainty. Relying on the reserve to choose a motor smaller than needed is not recommended. Conversely, if the real load continuously exceeds 315 kW, the right decision is to consider the 355 kW options at the top of the product range; in that case the frame and code information for 355 kW must be checked with the same care.

Logistics: topics to discuss with the order

Getting a large motor to site is part of the purchasing decision. Settling the following topics during the order prevents surprises on delivery day. The details are determined separately for each order.

• Site access: The full delivery address, whether the vehicle can enter the plant and reach the unloading point, access hours and whether the area requires a permit.
• Unloading equipment: Whether there is a forklift, crane or overhead crane on site to unload the motor and whether its capacity is sufficient. The motor must be lifted only by the lifting eyes on the frame; it is never lifted by the fan cover or the shaft.
• Packaging type: Whether the motor will be shipped on a pallet or in a closed wooden crate; if there is export, a long journey or storage in the open, this should be stated in advance.
• Transport arrangements: Who will carry out the transport and with what type of vehicle, insurance and delivery terms are discussed with the order.
• Storage after delivery: If the motor will not be installed immediately, it should be kept in a dry, vibration-free place and the shaft turned at regular intervals. For long storage, see our guide to keeping a spare motor on the shelf.
• Inspection on receipt: On delivery, check whether the packaging is damaged, that the nameplate data matches the order and that accessories (sensor connections, heater terminals, if any) are complete.

Example scenario: a 315 kW motor requirement on a grinding line

This example is fictional; it is not an actual customer project. Suppose it has been determined that the main drive of a grinding line, running through a gearbox, needs a 315 kW, 1,500 rpm motor.

• The candidate is the 315 kW motor with model code 355L-4. When requesting a quotation, "315 kW, 1,500 rpm, 355L-4" are written together; this removes the risk of confusion with the 355 kW model carrying the same code.
• If the plant is supplied at 400 V, the motor is connected in delta; cables and switchgear for the 526 A rated current are selected in the electrical design. For starting, the rating of the existing transformer and the starting condition of the geared load are assessed.
• If the motor room is humid, an anti-condensation heater is added to the order, and if winding temperature monitoring is wanted, the PTC or PT100 option.
• On the logistics side, vehicle access to the unloading point, the capacity of the site crane and the need for crated packaging are discussed with the order. If installation will take place a few weeks later, the storage conditions are prepared in advance.

If the same power is needed for a high-speed, directly coupled compressor or pump, the 355L-2 (2,982 rpm) is considered, and for a low-speed drive the 355L-6. Further information on planning for high power is in our article on planning 200 and 250 kW motors.

Information to send for a quotation

• Power, speed and model code together; the driven machine and its starting condition
• Supply voltage (400 V or 690 V), connection and starting method; transformer rating
• Mounting arrangement, flange size for a flange connection, transmission type
• Requested options: PTC/PT100 sensors, anti-condensation heater; number and cross-section of cables
• Delivery address, site access and unloading equipment information, packaging preference
• If replacing, a photo of the old motor's nameplate

When preparing your quotation request, you can use our article on the information to give when requesting a quote. Models at all power ratings and current prices are on the buy electric motors page; if you are looking for a model to replace an old motor, send us the motor nameplate. To settle the technical and logistical details together, reach us via our contact page.