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For a 160 kW three-phase asynchronous electric motor, the frame choice depends on speed: in the HEM Motor 2026 catalog, the 2-pole and 4-pole 160 kW models use a 315L frame, while the 6-pole model uses a 355M frame. This difference determines whether the base can stay as it is when a 160 kW (220 HP) motor replaces an old one. Below we explain why the frame differs, the steps for comparing with the existing base, and the general logic of bearing and lubrication maintenance on motors of this size.
160 kW models: which speed, which frame?
The values are taken from HEM Motor product records. All three models have a cast iron frame, IP55 protection and class F insulation, and their winding is 400/690 V (Δ/Y) for 50 Hz.
| Model | Poles / synchronous speed | Rated speed | IEC frame | Rated torque | Rated current (400 V) |
|---|---|---|---|---|---|
| 315L1-2 | 2 poles / 3,000 rpm | 2,980 rpm | 315L | 512.8 Nm | 265 A |
| 315L1-4 | 4 poles / 1,500 rpm | 1,488 rpm | 315L | 1,027 Nm | 271 A |
| 355M1-6 | 6 poles / 1,000 rpm | 990 rpm | 355M | 1,543 Nm | 281 A |
The first part of the model code gives the IEC frame: in "315L1-4", 315 is the frame number, L is the frame length letter, 1 is the power step within the same frame, and 4 is the number of poles. In the same family, the 185 and 200 kW 4-pole models are also in the 315L frame, and the 200 kW 6-pole 355M2-6 is in the 355M frame; so the frame chosen at 160 kW also serves as a reference if a power increase is considered later.
Why does the 6-pole version move up to a 355 frame?
The quantity that really determines the size of an asynchronous motor is not power but torque. To deliver the same 160 kW at 990 rpm, the motor must produce 1,543 Nm at the shaft; this is about three times the torque of the 2-pole model. Higher torque means a larger-diameter, longer rotor-stator package. When this package no longer fits inside the 315L frame, the next frame number is used.
As the frame grows, the cooling surface and bearing load change too. Because the 6-pole motor turns slowly, its fan moves less air; the large surface of the bigger frame helps make up for this. In the end, the right frame for 160 kW follows automatically from the machine's speed; what matters to the user is how this frame will sit on the base on site.
Comparing with the old motor's frame: shaft height
The IEC frame number indicates the height from the motor's foot base to the shaft axis in millimetres. Therefore, when a 355-frame motor replaces a 315-frame motor, the shaft axis rises by the difference between the frame numbers. Since the shaft of the driven machine is fixed, this difference directly upsets coupling alignment; the motor will not fit in place unless the base is lowered or rebuilt.
Care is needed even if the frame number stays the same but the letter changes. The letters S, M and L affect the frame length and therefore the longitudinal distance between the foot holes. For example, the 132 kW 4-pole model is in a 315M frame, while the 160 kW 4-pole model is in a 315L frame; the shaft height is the same, but the rear foot holes may fall at a different point. In that case it may be necessary to drill new holes in the base or use an adapter plate.
Will the base need changing? Step-by-step check
Carrying out this check before ordering avoids waiting after the motor arrives on site. We do not give dimension values as numbers in this article; the correct values for each frame and mounting type are in the 2D drawings on the technical drawings page. The order can be as follows:
- Read the nameplate: Note the frame code (e.g. 315M, 315L, 355M) and mounting type (such as B3, B35) on the old motor's nameplate. If the nameplate is illegible, you can estimate the frame number by measuring the shaft height.
- Measure the shaft height: Take the distance from the surface the feet sit on to the shaft centre. This value should come out close to the frame number.
- Measure the foot holes: Record the longitudinal and transverse distances between holes, and the distance from the shaft shoulder to the nearest hole axis.
- Check the shaft end: See whether the shaft diameter, shaft length and keyway match the coupling hub.
- Compare with the drawing: Put the frame drawing of the chosen model side by side with the old dimensions. If the difference is only longitudinal, the holes need shifting; if it is in height, base work is needed.
- Check the terminal box orientation: If the cable entry faces a wall or the machine, specify the box position in the order.
For the general frame–power correspondence, you can also look at our IEC frame – power table article. To compare frame and speed options, review suitable HEM Motor models and current prices.
