A: At Siemens, basically none. We can do fractional HP to tens of thousands of HP.

A: Efficiency is defined as energy used for work divided by total energy consumed. It is a ratio often expressed as a percentage. Losses are wasted energy. Losses are energy you pay for and can't use. So having a very efficient machine is great, but you can still run it in a way that produces too many losses. One of the best ways to minimize losses is by maximizing efficiency. But you can reduce losses without changing efficiency by implementing process controls like slowing down or switching off when not in use.

A: Currently 40HP. We have other integrated drive systems that go to thousands of HP. See usa.siemens.com/Simogear.

A: There are a lot of variables at work there. You have to look at the lifetime of the application and the torque/speed requirements. We can help you do that.

A: There are a lot of variables at work there. You have to look at the lifetime of the application and the torque/speed requirements. We can help you do that.

Also see http://www.industry.usa.siemens.com/drives/us/en/energy-efficiency/pages/energyefficiency.aspx]]>

**Shorten time to market:**Creating shorter innovation cycles, more complex products and greater data volumes**Increase flexibility:**Developing individual mass production, even in volatile markets, and with high productivity**Boost efficiency:**Energy efficiency and resource efficiency are critical competitive factors.

Two basic approaches are used to determine the required minimum shaft size for motors, both of which yield conservative results. One method calls for making the shaft large enough (and therefore strong enough) to drive the specified load without breaking. Mechanical engineers define this as the ability to transmit the required torque without exceeding the maximum allowable torsional shearing stress of the shaft material. In practice, this usually means that the minimum shaft diameter can withstand at least two times the rated torque of the motor.

Another way to design a shaft is to calculate the minimum diameter needed to control torsional deflection (twisting) during service. To engineers, this means the allowable twisting moment, or torque, is a function of the allowable torsional shearing stress (in psi or kPa) and the polar section modulus (a function of the cross-sectional area of the shaft).

Or, in metric units:

To see how much of a safety factor is built into the above equations, substitute 400 hp for the 200 hp power rating.

Since the calculated shaft diameter for a 200 hp motor is designed to withstand twice the rated torque, the shaft diameter of 2.371 in. is at the absolute minimum for the 400 hp rating.

A rule of thumb with this method is that the shaft must be large enough that it will not deflect more than 1 degree in a length of 20 times its diameter. To calculate the minimum shaft size to meet this specification, use the following equation:

Or, in metric units:

The minimum shaft diameters calculated by the torque transmission and torsional deflection methods are essentially the same for Examples 1 and 2. Still, a good approach is to calculate the size both ways, and then use the larger value as the absolute minimum.

The calculations for shaft diameter are not quite as straightforward for a vertical hollow-shaft motor. Two variables—the outside and inside diameters of the hollow shaft—are not standardized, making it impossible to simplify the calculation with a ratio. For this reason, it is easier to demonstrate if a specific hollow-shaft is sufficient for a given power rating.

For this example,

Theoretically, this shaft is capable of transmitting 1,700 hp, so it is more than sufficient for the 200 hp requirement.

The effect of a thinner wall is dramatic. The shaft with the 0.25-in. wall can carry less than 20% of the torque of the shaft with ½-in wall.

In any case, keep in mind that adding a keyway to an existing shaft weakens the shaft. Likewise, increasing the bore diameter of a hollow-shaft reduces the torque capacity. Consider modifying a shaft only with good engineering support. Even then, remember that the greater the consequence of failure, the more generous the safety factor should be. After all, who wants to use an elevator that was designed and built with no safety factor?

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