30–55 kW B5 Flange Electric Motor: Choosing 1500 or 3000 rpm

At DRG Motor, the 30, 37, 45 and 55 kW B5 flange motors are spread over four frames: 30 kW is 200L at both speeds, 37 kW is 200L at 3000 rpm but 225S at 1500 rpm, 45 kW is 225M at both speeds and 55 kW is 250M at both speeds. The flange outer diameter is 400 mm on 200L, 450 mm on 225S/225M and 550 mm on 250M, while the shaft varies with the pole count from 55×110 mm to 65×140 mm. In this band, the kW rating alone does not define the flange or the shaft.

All eight models have cast iron housings and belong to the three-phase asynchronous electric motors range; to compare their product pages side by side, visit the online motor shop. The next lower ratings are covered separately in 18.5 kW flange motor and 22 kW flange motor, and flange values for every frame from 63 to 355 are in the B5 motor flange dimensions table. This article focuses only on the selection differences between 30 and 55 kW.

Frame, shaft and B5 flange by power and speed

The table below combines DRG product records with the B5 large-flange rows of the DRG catalogue. P is the flange outer diameter, N the spigot (pilot) diameter, M the diameter of the bolt circle and S the hole diameter; they are four separate dimensions and each must be checked.

"1500 rpm" and "3000 rpm" are speed classes (synchronous speed). The nameplate speed is lower: the DRG-225M-4, for instance, is in the 1500 rpm class and its nameplate reads 1485 rpm. All models are 400/690 V (Δ/Y) connected.

Same power, different pole count: four ratings, four cases

What makes this power band tricky is that the 2-pole/4-pole difference shows up somewhere else at each rating. The table summarises it; the list below explains what it means on site.

• 30 kW: the DRG-200L1-2 and the DRG-200L-4 share the 200L frame, the 55×110 mm shaft and the 400 mm flange. Changing speed does not change the mechanical interface; only speed and torque differ.
• 37 kW: the rating that causes the most mistakes. The 3000 rpm DRG-200L2-2 is still on 200L (55×110 mm shaft, P 400 mm), while the 1500 rpm DRG-225S-4 moves up to 225S (60×140 mm shaft, P 450 mm). The flange outer diameter grows by 50 mm, the spigot goes from 300 to 350 mm and the bolt circle from 350 to 400 mm. At 37 kW, changing speed means changing the mating flange too.
• 45 kW: the DRG-225M-2 and the DRG-225M-4 are both 225M with the same flange, but the 2-pole shaft is 55×110 mm (key 16 mm) and the 4-pole shaft 60×140 mm (key 18 mm). Overall length also grows from 819 to 849 mm. Judging by the flange alone leads to a wrong coupling bore here.
• 55 kW: the DRG-250M-2 and the DRG-250M-4 are on 250M with the same 550 mm flange; shaft length is 140 mm on both, but the diameter is 60 mm (2-pole) versus 65 mm (4-pole). Because the key width is the same (18 mm), the two shafts are easy to confuse by eye; the G dimension (53 / 58 mm) only shows up with a caliper.

For the full list of shaft diameters by power see the motor shaft diameter by kW table; for shaft, key and coupling relationships see motor shaft diameter, key and coupling standards.

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Why is the 4-pole shaft thicker?

At the same power, a 4-pole motor turns at roughly half the speed, so its shaft carries roughly twice the torque. Torque is M = 9550·P/n (P in kW, n = nameplate speed in rpm). Torque values in the table come from DRG records; our formula check is in brackets.

At 45 kW, for example, the 2-pole model delivers 144.9 Nm and the 4-pole model 289.4 Nm; the shaft growing from 55 to 60 mm is the mechanical answer to that difference. Use the 400 V currents for cable and protection sizing together with the motor current chart and the motor cable size calculator.

B5 flange dimensions: 200L, 225 and 250M

The eight motors in this article use three flange sizes. In the DRG catalogue, 225S and 225M have identical flange dimensions; 225M and 250M have separate rows for 2-pole and for 4-pole and above, but what differs between those rows is the shaft, not the flange.

The difference between the FF (clearance-hole) large flange and the small flange is explained in B5 and B14 flange FF/FT difference. If the motor is to be fitted to a gearbox, compare not only the flange but also the gearbox input bore, key and permissible load with the gearbox manufacturer's data; the steps are in flange motor for gearbox selection.

The B14 small-flange table is not part of the DRG catalogue, so we do not give B14 or B34 dimensions for these ratings. If you need such a connection, send the existing flange's outer diameter, bolt circle, spigot diameter and thread size on WhatsApp and we will check it.

The limit of flange-only support: why B35 is common at higher power

A B5 motor has no feet: its whole weight, vibration and the reaction torque at start-up are transferred through the flange face and bolts to the mating part (machine housing, pump lantern or gearbox input). Mounted horizontally, the housing acts like a cantilever extending from the flange; the further the centre of gravity is from the flange, the higher the bending load on the flange and on the mating part.

The frames in this article are long: in the DRG catalogue, the LB dimension from the flange face to the rear end is 669 mm on 200L and 770 mm on 250M. As the frame grows, both weight and this cantilever length increase. That is why the following practice is common:

• B35 (feet + flange): the feet carry the weight into the base, the flange provides centring and shaft alignment. The mating part only aligns the motor instead of carrying it.
• B5 only: used when the mating flange and housing are designed to carry that weight and vibration. The limit is set by the mating part's manufacturer, not by the motor; confirm the motor weight with us and the permissible load with the mating part's manufacturer.
• Vertical flange mounting (shaft down/up): the load direction changes; always state the mounting position in the order.

For a B35 order, foot dimensions (A, B, C, H, K) and flange dimensions (P, N, M, S) are confirmed together. Mounting arrangements are compared in motor mounting types B3, B5, B14 and B35, and how to specify them is covered in the B3, B5 and B35 mounting order guide.

Dimensions to confirm before ordering

Two mistakes are most frequent in replacement orders: missing that the flange changes with speed at 37 kW, and looking at the identical flange at 45 and 55 kW without checking the shaft diameter. Working through this order reduces the risk.

For dimensioned drawings use the 2D technical drawings page; ordering steps by shaft and frame size are in the motor frame size order guide.

Frequently asked questions

If I replace a 37 kW 1500 rpm motor with a 37 kW 3000 rpm one, will the flange fit?

Not according to DRG data. The 1500 rpm DRG-225S-4 is on 225S with a P 450 / N 350 / M 400 mm flange, the 3000 rpm DRG-200L2-2 is on 200L with a P 400 / N 300 / M 350 mm flange, and the shaft changes from 60×140 to 55×110 mm. Doubling the speed also requires checking whether the machine suits that speed.

Do the 2-pole and 4-pole 45 kW B5 motors share the same flange?

Yes, both are 225M with flange P 450, N 350, M 400, S 18.5 mm. The difference is the shaft: 55×110 mm (2-pole) and 60×140 mm (4-pole).

Are the 55 kW 2-pole and 4-pole shafts the same length?

Shaft length is 140 mm on both, but the diameter is 60 mm and 65 mm. Choose the coupling or pulley bore accordingly.

Does the speed choice change the dimensions of a 30 kW flange motor?

Not in DRG data: the DRG-200L1-2 and the DRG-200L-4 use the same 200L frame, 55×110 mm shaft and 400 mm flange. What changes is speed, torque (96.8 / 194.2 Nm) and current.

Technical confirmation and ordering

DRG Motor is an electric motor manufacturer, supplier and seller. The quickest route to the right 30–55 kW model is to send us a photo of the existing nameplate, the shaft diameter and length, the flange P, N, M and S dimensions, and whether the motor is foot-and-flange (B35) or flange-only (B5) mounted. Dimensions for every frame are also in the DRG technical and product catalogue.

Send a photo of your current motor nameplate and we will find the suitable DRG model together.Send on WhatsApp

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Electric Motors Related to This Topic — Models and Current Prices

Suitability is not decided by power alone: compare the speed, voltage, mounting, shaft and fixing dimensions of your machine with the product data; if unsure, send us the nameplate of your current motor.

DRG-200L-4

30 kW Three-Phase Motor 1500 rpm – DRG-200L-4 Cast Iron

• 30 kW · 1500 rpm (4 poles)
• Cast iron frame · IEC 200L
• Shaft: 55 × 110 mm

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DRG-200L2-2

37 kW Three-Phase Motor 3000 rpm – DRG-200L2-2 Cast Iron

• 37 kW · 3000 rpm (2 poles)
• Cast iron frame · IEC 200L
• Shaft: 55 × 110 mm

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DRG-225S-4

37 kW Three-Phase Motor 1500 rpm – DRG-225S-4 Cast Iron

• 37 kW · 1500 rpm (4 poles)
• Cast iron frame · IEC 225S
• Shaft: 60 × 140 mm

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DRG-225M-4

45 kW Three-Phase Motor 1500 rpm – DRG-225M-4 Cast Iron

• 45 kW · 1500 rpm (4 poles)
• Cast iron frame · IEC 225M
• Shaft: 60 × 140 mm

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DRG-250M-2

55 kW Three-Phase Motor 3000 rpm – DRG-250M-2 Cast Iron

• 55 kW · 3000 rpm (2 poles)
• Cast iron frame · IEC 250M
• Shaft: 60 × 140 mm

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DRG-250M-4

55 kW Three-Phase Motor 1500 rpm – DRG-250M-4 Cast Iron

• 55 kW · 1500 rpm (4 poles)
• Cast iron frame · IEC 250M
• Shaft: 65 × 140 mm

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