One 160 kW motor vs two 129 kW motors

[GANESH SHETTI]

This is related to steel wire pulling machine. I have 2 cases.
In CASE-1: ONE MOTOR 160 kW
AND
CASE-2: TWO MOTORS 129 kW Each. i.e 2x129 kW

Which case would have an efficient pulling force and efficiency Case 1 or Case 2.

 

[russ_watters]

This is related to steel wire pulling machine. I have 2 cases.
In CASE-1: ONE MOTOR 160 kW
AND
CASE-2: TWO MOTORS 129 kW Each. i.e 2x129 kW

Which case would have an efficient pulling force and efficiency Case 1 or Case 2.

I'm not sure efficiency is really what you are after...

Are they operating the machine at tthe same speed? In general a motor is at its highest efficiency near it's highest load, so one motor would tend to be more efficient with all else being equal.

 

[GANESH SHETTI]

I'm not sure efficiency is really what you are after...

Are they operating the machine at tthe same speed? In general a motor is at its highest efficiency near it's highest load, so one motor would tend to be more efficient with all else being equal.

Let us assume same speed. which case is better in terms of pulling force and productivity and maintenance. Thank you

 

[russ_watters]

Let us assume same speed. which case is better in terms of pulling force and productivity and maintenance. Thank you

The two motors would be capable of more torque, but the torque is applied by the load. Are you changing the load? How can productivity change if speed isn't changing?

 

[Rive]

Well... what kind of motor we are talking about? Electric?

 

[GANESH SHETTI]

A rotating block/capstan is mounted on a bearing. The motor rotates the block and the block pulls the steel wire. The speed of the motor can be controlled by a regulator/control system. In machine number 1 I have 1 Block/motor (160 kW) pulling the steel wire and is machine number 2 I have 2 blocks/motors (129 kW each) pulling the steel wire. How can I conclude which machine would be better.

One point is that power consumption by the 2 motors will be more. I am concerned about the wear and tear, will it be less or more because of 2 motors.

 

[GANESH SHETTI]

Well... what kind of motor we are talking about? Electric?

Electric motors

 

[GANESH SHETTI]

The two motors would be capable of more torque, but the torque is applied by the load. Are you changing the load? How can productivity change if speed isn't changing?

A rotating block/capstan is mounted on a bearing. The motor rotates the block and the block pulls the steel wire. The speed of the motor can be controlled by a regulator/control system. In machine number 1 I have 1 Block/motor (160 kW) pulling the steel wire and in machine number 2 I have 2 blocks/motors (129 kW each) pulling the steel wire. How can I conclude which machine would be better.

One point is that power consumption by the 2 motors will be more.
I am concerned about the wear and tear, will it be less or more because of 2 motors.

 

[russ_watters]

A rotating block/capstan is mounted on a bearing. The motor rotates the block and the block pulls the steel wire. The speed of the motor can be controlled by a regulator/control system. In machine number 1 I have 1 Block/motor (160 kW) pulling the steel wire and in machine number 2 I have 2 blocks/motors (129 kW each) pulling the steel wire. How can I conclude which machine would be better.

Are you running the two machines at different speeds?

One point is that power consumption by the 2 motors will be more.

What makes you say that?

I am concerned about the wear and tear, will it be less or more because of 2 motors.

Again, it depends on if you run them at different speeds or if the 160kw motor is undersized.

 

[GANESH SHETTI]

What makes you say that? Answer: there are 2 motors 129 kW each...129+129=258 kW which is less than 160 kW.

Again, it depends on if you run them at different speeds or if the 160kw motor is undersized. Answer: 129+129 kW motor VERSUS 160 kW motor. Ok so if you consider speed which machine would be ideal for high speed at long run.

 

[russ_watters]

What makes you say that? Answer: there are 2 motors 129 kW each...129+129=258 kW which is less than 160 kW.

Again, it depends on if you run them at different speeds or if the 160kw motor is undersized. Answer: 129+129 kW motor VERSUS 160 kW motor. Ok so if you consider speed which machine would be ideal for high speed at long run.

The kw rating is the peak output mechanical power the motor can provide. It has very little to do with the actual operating input electrical kw. The actual operating input electrical kw depends primarily on the actual operating mechanical output kw.

The reason the ratings are odd numbers is they are conversions from horsepower: 129 kw is 175 horsepower. Output. And it will draw a peak electrical input of about 140 kw.

 

[GANESH SHETTI]

The kw rating is the peak output mechanical power the motor can provide. It has very little to do with the actual operating input electrical kw. The actual operating input electrical kw depends primarily on the actual operating mechanical output kw.

The reason the ratings are odd numbers is they are conversions from horsepower: 129 kw is 175 horsepower. Output. And it will draw a peak electrical input of about 140 kw.

What is the concluding factor for these machines?

 

[russ_watters]

What is the concluding factor for these machines?

I don't understand what you are asking. Can you rephrase and be more descriptive?

 

[GANESH SHETTI]

I don't understand what you are asking. Can you rephrase and be more descriptive?

Machine A --- 160 kW motor power --- One motor --- pulling 8 mm steel wire at 7 meter/second speed --- working 20 hours/day --- 25 days/month --- producing 2700 tonnes/month (given by manufacturer)

Machine B --- 129 + 129 kW motor power --- Two motors --- pulling 8 mm steel wire at 7 meter/second speed --- working 20 hours/day --- 25 days/month --- producing 2900 tonnes/month (given by manufacturer)

Which Machine is the better. what other information do i require to make an excellent comparison report. thank you

 

[Tom.G]

what other information do i require to make an excellent comparison report.

From the data you have supplied, just keep a spare motor (and other parts) for either machine.

Other things to consider: are parts easily available, how easy are they to repair, cost of employee training, what is the reputation of the manufacturer, is on-site factory service available.

Also consider the total cost of purchase, including cost of capital, any modifications to your building, and the expected life of the machine, against the 7% difference in product output.

Overall, this is largely a business decision with input from Engineering... and no one here is in your business environment.

 

[russ_watters]

Machine A --- 160 kW motor power --- One motor --- pulling 8 mm steel wire at 7 meter/second speed --- working 20 hours/day --- 25 days/month --- producing 2700 tonnes/month (given by manufacturer)

Machine B --- 129 + 129 kW motor power --- Two motors --- pulling 8 mm steel wire at 7 meter/second speed --- working 20 hours/day --- 25 days/month --- producing 2900 tonnes/month (given by manufacturer)

Which Machine is the better. what other information do i require to make an excellent comparison report. thank you

If you are just asking about energy use, ask the manufacturers what the operating electrical load is.

...also since the calculations are the same but have a different answer, you should check their calculations. How much does an 8mm steel wire weigh per meter? Perhaps there is a hidden assumption or rounding difference.

...you could also directly ask the manufacturers why their one/two motor design is better and see what they say.

 

[Baluncore]

Which Machine is the better. what other information do i require to make an excellent comparison report. thank you

In both cases, an 8mm diameter wire is being pulled at 7 metres per second, for 25 days per month.
You should explain why one machine produces 2700 and the other 2900 tonne per month.

You need to find out how much power is actually needed to pull the 8mm wire at 7 metres per second. Do you have one you can measure ?

You need to find the relationship between load in kW and slip % below synchronous speed for the available motors.

 

[CWatters]

What's the tension in the wire? I think with that and the velocity you can calculate the load.

Can you measure the power consumption of the two machines? With that info it should be possible to calculate and compare the efficiency of the two machines.

I think it will be difficult to say which will require less maintenance. I think you would need to know what the load is on the bearings and what effect the manufacturer thinks that will have in bearing life. Do the smaller motors have smaller bearings?