# HP or PWOER Loss between 2 different sized Pulleys?

• trillionex
In summary: It could just mean that the motor is being used at a higher rpm than it would be at if the pulley was the same size.
trillionex

hello guys..!
i have one pulley of 8" (Driver) and another one 10" (Driven) he driver pulley is driven by 2Hp motor, so is there any equation or formula to calculate the Hp loss or power loss from 2Hp?

In the ideal case, there is no power loss. For a real situation, you'd need to know more to be able to figure out what the power loss was.

so if 10' pulley is kept on load then it would get 25% less Hp then the input Hp at 8"pulley as it is 25% bigger in size?

Pulley size will affect torque and rate of rotation (trading one for the other), but will have little effect on power. Power losses are due to losses in the pulley bearings and friction with the belt.

trillionex said:
so if 10' pulley is kept on load then it would get 25% less Hp then the input Hp at 8"pulley as it is 25% bigger in size?

Nope. The power would be the same, but the torque and rpm would change.

As said, ideally the power loss is zero regardless of the pulley size. Realistically, it is a few percent, depending on the configuration.

Yaa russ the change is few percent but i wana calculate that few percent..

Then you need to know more than just the size difference. That will depend on the bearings and belt or cable used.

Ok so suppose if 8" pulley is driven by 2 hp and 10" pulley has to also drive 2hp load then would 10" pulley will be able to drive that load with full 2hp or 1.75hp or 1.5hp?

trillionex said:
Ok so suppose if 8" pulley is driven by 2 hp and 10" pulley has to also drive 2hp load then would 10" pulley will be able to drive that load with full 2hp or 1.75hp or 1.5hp?
You're not understanding: it could literally be anything below 2 hp in a real-world situation and it can't be calculated exactly, only estimated. If you have a real-world application and you need to know so you can select a motor, use 10% to be safe...and then increase the motor size by another 20% to be safer.

russ_watters said:
You're not understanding: it could literally be anything below 2 hp in a real-world situation and it can't be calculated exactly, only estimated. If you have a real-world application and you need to know so you can select a motor, use 10% to be safe...and then increase the motor size by another 20% to be safer.

ok got it...i just needed to confirm that loss does occur and that also quite significant one...as u said it trades torque for rpm...others were saying that there is so little loss that it wuldnt even matter but i think that loss count matters

trillionex said:
ok got it...i just needed to confirm that loss does occur and that also quite significant one...as u said it trades torque for rpm...others were saying that there is so little loss that it wuldnt even matter but i think that loss count matters
Right, but just so we're clear, trading torque for rpm is not loss.

Yaa russ, thnx fr the help, appreciate it

trillionex said:
ok got it...i just needed to confirm that loss does occur and that also quite significant one...as u said it trades torque for rpm...others were saying that there is so little loss that it wuldnt even matter but i think that loss count matters

What you don't seem to be understanding is that trading torque for RPM does not necessarily indicate a loss.

## What causes power loss between two different sized pulleys?

The main cause of power loss between two different sized pulleys is friction. As the belt or chain moves between the pulleys, it experiences friction which results in energy loss. This can be affected by factors such as the type of material used for the pulleys and the tension of the belt or chain.

## How is power loss calculated between two different sized pulleys?

Power loss between two different sized pulleys can be calculated using the formula P = (T1 - T2) x V, where P is the power loss, T1 and T2 are the tensions on either side of the belt or chain, and V is the velocity of the belt or chain. This formula takes into account the tension and speed of the system, as well as the length of the belt or chain.

## What is the relationship between pulley size and power loss?

The relationship between pulley size and power loss is inverse. This means that as the size of the pulleys increases, the power loss decreases. This is because larger pulleys have a larger surface area for the belt or chain to wrap around, reducing the amount of friction and energy loss.

## Can power loss be reduced between two different sized pulleys?

Yes, power loss can be reduced between two different sized pulleys by using materials with low friction coefficients for the pulleys, maintaining proper tension on the belt or chain, and ensuring that the pulleys are properly aligned. Additionally, using larger pulleys and increasing the number of pulleys in the system can also help reduce power loss.

## How does power loss affect the efficiency of a system?

Power loss can greatly affect the efficiency of a system. The more power that is lost between two different sized pulleys, the less efficient the system becomes. This means that less energy is being transferred from the input to the output, resulting in a decrease in overall performance and efficiency of the system.

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