7.5 kW Flanged Motor Price: Flange Dimensions on 132S, 132M and 160M Frames

A 7.5 kW flanged motor does not come with one single flange size; the speed decides it. The 3000 rpm DRG-132S2-2 sits in a 132S frame and the 1500 rpm DRG-132M-4 in a 132M frame, and both carry the same B5 flange: P 300 mm outer diameter, M 265 mm bolt circle, N 230 mm spigot diameter, shaft 38 × 80 mm. The 1000 rpm DRG-160M-6 moves up to a 160M frame, with a P 350 / M 300 / N 250 mm flange and a 42 × 110 mm shaft.

The reason the frame grows is torque. The same 7.5 kW means 24.4 Nm at 2930 rpm, 49.1 Nm at 1460 rpm and 73.8 Nm at 970 rpm; at low speed the shaft has to be thicker and the rotor longer. So when you look for a fan or extractor motor, first fix the speed the impeller needs, then the frame and flange that belong to that speed.

Aluminium and cast iron versions of all three models are listed on our Buy Electric Motors Online page; the table below shows which code matches which mounting dimension.

Frame and B5 flange by speed

The values are the catalogue IM B5 (large flange, FF) dimensions. S is the flange hole diameter, T the spigot length and LA the flange thickness. Flange and shaft are identical on 132S and 132M; only the overall length differs (L 438 mm and 476 mm). The 2-pole and 4-pole models therefore fit the same fan housing, but the 4-pole one needs 38 mm more axial space. For the flange data of every frame size, see our B5 motor flange dimensions table.

What a flanged frame brings to fans and extractors

On direct-drive fans the impeller is mounted on the end of the motor shaft. The motor is then both the drive and the bearing of the impeller; bolting it to the fan housing or sheet-metal base through the flange rather than the feet fixes the gap between impeller and scroll via the spigot diameter. With a foot-mounted motor that gap depends on the base welding, the shim pack and the bolt tightening sequence.

Three values matter for the impeller-to-shaft connection: shaft diameter D, key width F and the tapped hole DH at the shaft end. On the 132 frame D is 38 mm, F 10 mm, DH M12X28; on the 160M frame D is 42 mm, F 12 mm, DH M16X36. An impeller whose hub bore and keyway were not machined to these values cannot be moved to a model of another speed. Our article on B5 flanged fan motor supply covers the same subject from the purchasing side.

Vertical mounting: shaft down or shaft up?

Roof extractors and some smoke exhaust fans run with the motor vertical. The vertical positions of a flanged motor are described by IEC mounting codes: in IM V1 the flange is on top and the shaft points down; in IM V3 the shaft points up. In both cases the impeller weight and the axial thrust of the fan go straight into the bearings, unlike in horizontal mounting.

• Shaft down (V1): the impeller hangs below the motor. Rain and condensation do not run towards the shaft exit, but the impeller weight pulls on the front bearing. This is the most common layout on roof extractors.
• Shaft up (V3): the impeller sits above the motor. Because the shaft exit faces upwards, water and dust settle towards the seal; shaft sealing and the top cover become more critical.
• Horizontal (B5): the usual position for wall extractors and duct fans; the impeller weight is carried as a radial load.

State clearly in your order that the motor will run vertically and which way the shaft will face. The bearing is 6208-ZZ-C3 on the 132 frame and 6309-C3 on the 160M frame; check with the fan builder that impeller weight and axial thrust stay within what these bearings can carry.

Fan law: how the wrong speed overloads 7.5 kW

On centrifugal and axial fans the power absorbed by the impeller changes with the cube of the speed. If an impeller designed for 1460 rpm and drawing 7.5 kW is fitted to the 2930 rpm DRG-132S2-2 just because the flange matches, the required power rises roughly (2930 / 1460)³ ≈ 8.1 times; the motor trips its overload within seconds and the impeller may exceed its mechanical limit. The other way round, running the same impeller with the 970 rpm DRG-160M-6 drops the power to about 0.29 times and the airflow ends up far below the target.

This calculation shows why 132S and 132M sharing one flange can be a trap: the connection fits, the aerodynamics do not. Go by the speed marked on the impeller or the fan maker's data sheet; to check with your own airflow and pressure values, use the pump and fan motor power calculator.

Electrical side: current and starting

All three models are wound for 400/690 V (Δ/Y) and are connected in delta on a 380 V network. Rated current at 400 V is 13.7 A for 2 poles, 14.3 A for 4 poles and 15.4 A for 6 poles. cos φ is 0.88, 0.84 and 0.79 respectively, which explains the slightly higher current of the low-speed model.

Fan impellers have high inertia and take long to start. Starting current is 7.9 (2-pole), 7.5 (4-pole) and 7.0 (6-pole) times the rated current. With such long acceleration, overload relay setting and starting method must be considered together; the star-delta starting page and the overload, fuse and contactor selection tool explain both topics separately. Leave wiring and panel work to a qualified electrician.

Technical factors that set the price

What separates one 7.5 kW flanged motor from another is purely technical: number of poles and the resulting frame (132S, 132M or 160M), housing material (aluminium or cast iron), mounting (B5 flange or B35 feet + flange) and special requests such as vertical operation. The 6-pole model moving to a 160M frame means the same power delivered in a larger construction. To see current figures, simply open the relevant code among the 120 models in our online shop.

Checklist before ordering a fan motor

• What is the design speed of the impeller: 2930, 1460 or 970 rpm?
• Is the spigot recess in the fan housing 230 mm (132) or 250 mm (160)?
• Is the bolt circle 265 mm or 300 mm; are the holes 14.5 mm or 18.5 mm?
• Is the impeller hub bored for a 38 mm or a 42 mm shaft; is the key 10 mm or 12 mm?
• Is the mounting horizontal, shaft down (V1) or shaft up (V3)?
• Is there axial room for a 438, 476 or 608 mm motor length?
• Should the housing be aluminium or cast iron?

Motors that fit the 7.5 kW flange

• DRG-132S2-2 – 7.5 kW – 2930 rpm – 132S aluminium
• DRG-132M-4 – 7.5 kW – 1460 rpm – 132M aluminium
• DRG-160M-6 – 7.5 kW – 970 rpm – 160M aluminium
• DRG-132S2-2 – 7.5 kW – 2930 rpm – 132S cast iron
• DRG-132M-4 – 7.5 kW – 1460 rpm – 132M cast iron
• DRG-160M-6 – 7.5 kW – 970 rpm – 160M cast iron

Click to see current prices and order these motors nowSEE PRICES →

Frequently Asked Questions

What is the flange diameter of a 7.5 kW motor?

On the 132S and 132M frame models (DRG-132S2-2 and DRG-132M-4) the B5 flange outer diameter P is 300 mm, the bolt circle M 265 mm and the spigot N 230 mm. The 6-pole DRG-160M-6 is in a 160M frame with a P 350 / M 300 / N 250 mm flange.

What is the shaft size of a 7.5 kW motor?

The shaft is 38 × 80 mm on the 3000 and 1500 rpm models and 42 × 110 mm on the 1000 rpm model. Key width is 10 mm and 12 mm respectively.

Can a 10 HP extractor motor be mounted vertically?

A flanged 7.5 kW motor can be used vertically; specify shaft down (IM V1) or shaft up (IM V3) in the order and confirm with the fan builder that the impeller weight suits the bearings.

Can a 3000 rpm motor replace a 7.5 kW 1500 rpm motor?

Even with the same flange, doubling the speed of a fan or pump impeller raises the required power roughly 8 times. Do not make this change unless the impeller is selected for the new speed.

Send us the flange dimensions of your fan housing or the bore of the impeller hub and we will pick the right code together: +90 (542) 666 11 11 · [email protected] · contact page. You can compare all 7.5 kW models in the Buy Electric Motors Online section.