Fan & Cooling Tower Drive
Motor, Gearbox & VSD Selection
Fan drives are characterised by high inertia and long run-up times, and cooling tower gearboxes carry significant axial thrust in a wet, corrosive atmosphere at the end of a long driveshaft.
Send us the fan duty, speed and site conditions. We select the motor, gearbox or direct drive, coupling and starter, and quote them as one package with the run-up time and thermal rating stated.
What we need from you to select this drive
The more of this you send, the faster and more accurate the selection. If you only have part of it, send what you have — we will tell you what is still missing.
Duty data and site conditions
| Fan type | Centrifugal, axial, induced or forced draft, cooling tower fan |
|---|---|
| Duty point | Flow in m³/h or m³/s, static and total pressure in Pa, gas density and temperature |
| Speed | Fan speed in rpm, and whether the speed is fixed or variable |
| Inertia | Fan inertia in kg·m² or the run-up time — this sizes the motor and starter |
| Operating pattern | Running hours, starts per hour, whether reverse operation is needed |
| Power supply | Voltage, frequency, phases, permitted voltage drop, medium-voltage requirement |
| Site conditions | Ambient temperature, altitude, humidity, corrosive atmosphere, hazardous area |
| Mechanical layout | Driveshaft length and arrangement for cooling towers, mounting position |
How we select it
- 1
Confirm the duty point and the absorbed power at the specified gas density and temperature.
- 2
Check the fan inertia and run-up time against the motor thermal capability and the starting method.
- 3
Select the transmission — direct drive, belt drive, or a cooling tower gearbox — against speed and layout.
- 4
Verify the critical speed of the shaft assembly and confirm the axial and radial load ratings.
- 5
Select the VSD or starter and quote the package with the ratings stated.
Selection points that decide the outcome
Run-up time sets the rating
Large fans accelerate slowly. The motor has to carry the starting current for the whole run-up without overheating — check this rather than only the steady-state power.
Cooling tower axial thrust
Cooling tower gearboxes carry the fan weight and the axial thrust. Confirm both ratings, along with the oil temperature in high ambient conditions.
Critical speed of the driveshaft
Long cooling tower driveshafts have a critical speed that must sit outside the operating range. Confirm it during selection.
Gas density and temperature
Fan absorbed power scales with gas density. State the actual operating temperature, especially for induced draft fans.
VSD and torsional resonance
Variable speed operation can excite torsional resonances in a long shaft system. Ask for a torsional check when a VSD is applied to a cooling tower drive.
An indicative package
An example of how a selection comes together. Your figures will differ — this is to show the level of detail we return with a quotation, not a fixed configuration.
Duty
Cooling tower fan Ø 8.5 m · 132 kW · fan speed 130 rpm · wet, humid atmosphere, 45 °C
Package
- Motor: 132 kW, 6- or 8-pole, IP55, high-ambient and corrosion-protected design
- Gearbox: Flender cooling tower gearbox rated for the fan weight, axial thrust and oil temperature at 45 °C
- Driveshaft: hollow shaft with the critical speed confirmed outside the operating range
- Control: VSD with a torsional check, or a soft starter for fixed-speed operation
- Monitoring: vibration and oil temperature monitoring on the gearbox
What we supply for this duty
Cooling tower gearboxes
- Flender cooling tower gearboxes
- Flender helical and bevel-helical gear units, 3,100 – 1,400,000 Nm
- Flender FLENDER ONE
Motors
- Innomotics SIMOTICS low-voltage and medium-voltage motors
- WEG W22, W40 ODP and W51 HD
- ABB IEC and NEMA motors
Variable speed drives
- Siemens SINAMICS G120X and G150
- ABB ACS580, ACS880 and medium-voltage ranges
- WEG CFW11 and CFW701
Couplings and driveshafts
- Flender ARPEX and ZAPEX couplings
- Flender N-EUPEX and ELPEX couplings
- Cooling tower driveshafts
Control and monitoring
- Siemens SIMATIC S7-1200 / S7-1500
- B&R X20 system
- Vibration and oil temperature monitoring
Ratings we can supply
Typical ratings available
| Motor power | 0.12 kW to multi-megawatt; medium-voltage for large induced draft fans |
|---|---|
| Gearbox torque | Flender FZG: 3,100 – 1,400,000 Nm, 28 sizes, ratio i = 1.25 – 450 |
| Output speed | Cooling tower fans typically 100 – 200 rpm; matched to the fan |
| Medium-voltage drive | Innomotics Perfect Harmony GH180: 2.3 – 11 kV, 0.12 – 25 MW |
| Ambient | High-ambient and corrosion-protected designs for wet tower environments |
Brands we supply
Browse by category
Related applications
Other Brands Available on Request
Beyond the brands shown here, we also source and supply spare units and parts for most international and Chinese industrial brands. Not sure what you have? Send us a photo of the nameplate — we will identify the unit and quote the original part.
Why work with us
- We select the whole drive train — motor, gear unit, coupling, starter and brake — as one matched package.
- You send the duty data; we return the ratings, service factors and alternatives in writing.
- We supply Siemens, Innomotics, Flender, ABB, WEG and B&R, so selection follows your duty, not one catalogue.
- Spare parts and replacements for the same units are available afterwards.
Service & support
Remote and on-site support available, from installation supervision to commissioning and troubleshooting.
What we need from you to quote
For replacements, send a nameplate photo — we identify the exact unit and quote the original part.
- Duty data — power, torque, speed, flow or head, and duty cycle
- Supply voltage, frequency and starting method
- Preferred brand, and your required delivery window
- Quantity, destination port and required delivery date
Answers before you ask
Frequently asked questions
Do you supply cooling tower gearboxes with the driveshaft?
Yes. We supply Flender cooling tower gearboxes together with the motor, driveshaft and control, and confirm the axial thrust and critical speed as part of the selection.
Can a variable speed drive be applied to a cooling tower fan?
Yes, but the shaft system should be checked for torsional resonance first. We include that check when a VSD is applied to a long driveshaft arrangement.
Do you only supply the eight brands shown on your homepage?
No. We source and supply spare units and parts for most international and Chinese industrial brands, not only the eight brands shown on this site.
I do not know the exact model number. Can you still quote?
Yes. Send us a photo of the nameplate and we will identify the exact unit before preparing the quotation for the original part.
Do you supply genuine original manufacturer parts?
Yes. We supply genuine original manufacturer parts. Send us a photo of the nameplate and we can identify the exact unit before quoting, so you do not need to look up a model number.
Do you provide installation guidance, commissioning and after-sales support?
Yes. We provide installation guidance, commissioning support and after-sales support, remotely or on site depending on your project.
What is the delivery time?
Lead time depends on the product and configuration. We confirm the delivery schedule together with the quotation, so you have a firm date before you order.
Which export documents and certificates can you provide?
We can provide applicable CE and ISO documentation, certificates of origin, packing lists and test reports according to the requirements of your destination country.
What payment terms and incoterms do you work with?
We accept T/T and L/C payment, and quote FOB, CIF or EXW terms to suit your project.
Send the duty data and we will select the package
We return a selection with the ratings, service factors and alternates stated — so you can compare before you buy.
Request a Quotation