Belt Drive vs Direct Drive

You must consider the ratio of the drive-to-driven belt pulleys.

By utilizing a belt drive between the VFD and the fan the mechanical load on the prime mover (VFD) is being reduced.

Duplicate thread.

it's still a dumb question. the amount of "work" doesn't care about RPM or type of motor. the load will determine how many amps are required, NOT RPM the amount of power required is constant if the load is constant. save money another way

Yeah, my question on the other thread suggests the same.

Where are you measuring voltage and amperage--before or after the VFD?

I would say that there must be an error in the VFD drive response curve,versus the power curve of the motor and fan.

A lower frequency on the motor will increase amps,same as an increase in load.

Without changing anything,your most economical mode is with belt drive,but with a properly matched motor/drive combination you should get higher efficiency from a direct drive.

If you have simply added a VFD to an existing motor,you are in for a lot of unexpected problems with bearings,due to high frequency eddy currents circulating through the ball bearings,which can cause pitting,and the insulation cannot always withstand the high frequency spikes.

I advise getting proper drive/motor combination,and consider the fan curve when specifying.

In the unlikely case this is just another amazingly similar post to the one already asked anonymously (and answered), my response remains the same.

http://cr4.globalspec.com/comment/1128095/Re-direct-drive-vs-belt-drive

A "Direct Drive" pump has a hollow shaft, which simply slides onto the drive shaft of a motor or engine. The flange on the pump is mounted to the face of the engine or shaft end of the motor. Normal gasoline engine speed is about 3450 RPM. Since the pump is connected directly to the engine shaft, the pump RPM is the same as the engine RPM. Electric motors typically will turn a direct drive pump at 3450 RPM or 1725 RPM. Direct drive pumps allow for a more compact designed pressure washer. Another advantage is that this drive system is simple, with fewer moving parts; therefore less expensive. The disadvantage is by having the pump spin as much as the engine or motor, the bearings and other parts get more wear and tear, reducing the life span of the pump. Direct drive pressure washers transfer the vibration of the engine or motor directly to the pump.

A "Belt Drive" pump has a pulley mounted to its solid shaft and is driven by one or more belts that are attached to a pulley on the motor or engine. The pulley system allows these pumps to turn at a much lower RPM than a direct drive pump (typically 900-1400 RPM). The belt drive pump crankcase has a larger oil capacity. This, combined with the lower RPM of the belt drive pump, allows the pump to run much cooler than a direct drive pump. The pump is isolated from the heat of the engine or motor, also. Belts and pulleys also absorb vibration, reducing pump fatigue. Because of these factors, most heavy use pressure washer applications will demand a belt drive pump. The disadvantage of this system is there is some loss of efficiency due to the additional friction from the belts and pulleys. Plus maintenance is required occasionally to adjust the belts.

??? Who said anything about engines?

A "Direct Drive" pump has a hollow shaft, which simply slides onto the drive shaft of a motor or engine. The flange on the pump is mounted to the face of the engine or shaft end of the motor.

Benefits of Direct Drive:

• Compact Design
• Lower Acquisition Cost

A "Belt Drive" pump has a pulley mounted to its solid shaft and is driven by one or more belts that are attached to a pulley on the motor or engine.

Benefits of Belt Drive

• Vibration Absorption
• Lower RPM
• Lower Operating Temperature
• Longer Life

The amount of power needed to drive a <...Fan...> is proportional to about the cube of the tip speed. Does that help?

The <...reasons...> a <...belt drive...> requires more <...power...> is that there is a <...power...> loss in the <...belt...> and its pulleys, which doesn't happen in <...direct drive...>.