Converting KW to Te

[anonymous-user]

Okay, my brain is mush right now. Anyone know the calcs to work out how many metric tons 8 x 120KW electric motors can vertically lift? All the motors would be driving a single rack via a pinion on each motor shaft (assume no gearbox for the calc).

[V8LM]

Depends how fast doesn't it?

ETA: 960 kW is 960,000 N m s-1 which is 96 tonnes at 1 m s-1.

Edited by V8LM on Thursday 22 August 22:21

[Simpo Two]

And efficiency of motors?

[anonymous-user]

And the efficiency of the geartrain. And the fact the motors only make their full power at a particular rated speed.

[anonymous-user]

Cheers My guess was about 100Te so not far off.

[V8LM]

fatbutt said:

Cheers My guess was about 100Te so not far off.

They could lift a lot more than that, or struggle with much less.

[Simpo Two]

You need to buy 8 x 120KW electric motors, and some weights, and find out properly. Everything else is approximations based on assumptions, hence not worth the trouble

[anonymous-user]

V8LM said:

They could lift a lot more than that, or struggle with much less.

Assume a sinusoidal wave (+/- 2.5m, 10 second peak to peak period) for the load movement. My latest version of the concept now has 16 x 125KW motors - any ideas on how much it can lift based on that sine wave?

[V8LM]

power = force * velocity

The velocity of the mass is approx 1.57 m/s at its fastest in the middle of the wave

16 x 125 kW motors = 2 000 000 W

2 000 000 / 1.57 = 1 274 000 N

1 274 000 / 9.8 = 130 000 kg

= 130 tonnes

All the caveats above apply - this assumes the motors and their drive is 100 % efficient, which they can't be.

All of the above may also be bks. Probably is from me.

Edited by V8LM on Thursday 29th August 20:56

[anonymous-user]

V8LM said:

power = force * velocity

The velocity of the mass is approx 1.57 m/s at its fastest in the middle of the wave

16 x 125 kW motors = 2 000 000 W

2 000 000 / 1.57 = 1 274 000 N

1 274 000 / 9.8 = 130 000 kg

= 130 tonnes

All the caveats above apply - this assumes the motors and their drive is 100 % efficient, which they can't be.

All of the above may also be bks. Probably is from me.

Edited by V8LM on Thursday 29th August 20:56

Hi - I'm sure its not bks but what I can't get my head around is that a crane supplier has a HPU driving a winch and that winch is rated at 2.2MW. The winch can pull a 250Te load when subjected to the wave I described above. Maybe its because their system uses accumulators to store some of the regenerated kinetic energy on the downward part of the sine wave and offset the power consumption using stored energy. It's all voodoo black magic as far as I can see.

[V8LM]

fatbutt said:

Hi - I'm sure its not bks but what I can't get my head around is that a crane supplier has a HPU driving a winch and that winch is rated at 2.2MW. The winch can pull a 250Te load when subjected to the wave I described above. Maybe its because their system uses accumulators to store some of the regenerated kinetic energy on the downward part of the sine wave and offset the power consumption using stored energy. It's all voodoo black magic as far as I can see.

Sine wave, or triangular wave?

ETA: Even then, I don't get it. Raising 250 000 kg by 5 m is 250 000 x 5 x 9.8 = 12 250 000 J. To do this in 5 seconds is 2 450 000 J/s = 2.45 MW.

ETATA: This assumes that Te = tonnes. I don't know what Te is - it's a load, isn't it? Is 250 Te = 250 tonnes or 25.5 tonnes in 9.8 g? If the latter, then all is well.

Edited by V8LM on Thursday 29th August 23:10

[anonymous-user]

V8LM said:

Sine wave, or triangular wave?

ETA: Even then, I don't get it. Raising 250 000 kg by 5 m is 250 000 x 5 x 9.8 = 12 250 000 J. To do this in 5 seconds is 2 450 000 J/s = 2.45 MW.

ETATA: This assumes that Te = tonnes. I don't know what Te is - it's a load, isn't it? Is 250 Te = 250 tonnes or 25.5 tonnes in 9.8 g? If the latter, then all is well.

Edited by V8LM on Thursday 29th August 23:10

Sine wave. Te is 1000Kg.

[anonymous-user]

This might help you understand the issue: http://www.macartney.com/video-ahc-electrical-winc...

[V8LM]

Thanks for that. Still don't see how they can do at least 2.45 MW of work with a 2.2 MW motor.