史蒂夫梅尔
Steve Meyer是总统，坚实的技术（Lakewood，Co）
What’s wrong with specifying horsepower for motors, particularly in motion control systems?Plenty. First, horsepower is a unit of measure for doing work, the rate at which power is consumed. If you were to measure power in a typical machine during normal operation, you would see it vary considerably, especially when starting and stopping loads. Second, horsepower is a time-dependent measure that can mask certain operating conditions, which may be critical to the successful operation of a control system, especially a mechatronic implementation.
More often than not, specifying electrical equipment in terms of horsepower can pose a serious problem. For example, an engineer had a machine nameplate containing detailed information concerning a 2-hp motor that ran a pump. He wanted to use a 2-hp variable frequency drive to run it, but the drive he selected would not start the motor. He then tried a 5-hp drive to handle a larger starting current. He discovered that the 5-hp drive was not much better, but he said it would start the motor if he “coaxed” it.
He finally connected an ammeter to the motor and made a strip chart recording of the starting current, which turned out to be ten times the running load. The results are not so surprising if you consider that the pump is cast iron with a rubber impeller and intended to be started when dry. Because of the high dry friction, the torque required was huge, but as soon as liquid hit the pump cavity, the torque requirement dropped to about 3 A, well within the 2-hp rating. Eventually, a 10-hp drive solved the problem.
Which Watt?
与流行的看法相反,詹姆斯·瓦特没有发票ent the steam engine, though he is credited with many inventions. It was Thomas Newcomen’s version of the steam powered water pump that was in widespread use throughout England for almost 100 years when Watt was asked to make repairs on one in 1764. It was Watt’s improvement of the Newcomen pump that made the steam engine the prime mover of the Industrial Revolution. The speed governor, the first planetary gear reducer, and many other patents bear his name, as well as the unit of energy we use to measure power.
然而，在许多发明中，甚至更重要。当瓦特和他的伴侣试图销售他们改进的蒸汽机时，他们提出了这个词，马力，这将有助于人们更好地了解蒸汽机会节省多少时间和努力。
Although the precise definition changed slightly over time, it is accepted to mean the ability of a horse to lift a 550 lb weight one foot in one second. That is:
746 W = 1 hp
在哪里：
1 hp = Torque (ft-lb) X speed (rpm)/5250
只有在以相同速度运行时，才能在马力方面相互比较电动机。在两个电机和发动机中，马力是一种速度依赖的工作单位。可以通过增加速度来操纵给定任务所需的电动机尺寸。通常，在某些限制内，只需选择具有更高速度的电动机即可增加马力额定值。这使得较高额定速度的电动机较小的电动机以较低的速度完成与较大电动机相同的工作量。大多数恒定速度电机设计用于以1800 RPM操作，因此这提供了基准，以便在马力评级方面比较AC电机和变速驱动。讨论设备的惠普等级时，确保每个人都同意1800 rpm是他们的参考速度。
Torque is force
考虑扭矩，作用在距离（半径）处的力，使轴旋转。与HP相比，扭矩不需要单位时间。但我们经常互换地指的是电力，扭矩和马力，这导致更多的混乱。
It is essential to understand the concept of work when applying electric motors to any machine. Electric motors can be designed to operate at low speeds for direct drive applications that run from zero to 500 rpm, or for high-speed applications that run at 20,000 rpm or more. Dental drills, for example, traditionally used 100,000 rpm air motors that tended to run noticeably slower under load. By comparison, new dental drive systems run at 50,000 rpm and use miniature brushless dc drives and closed-loop control circuits to compensate the speed droop common to the air-driven tools.
Electrical to mechanical energy
The basic goal of an ac motor connected directly to line power is to produce a rotating load. The process of converting electrical power in the motor to mechanical power in the load generates heat, and the maximum amount that can be dissipated determines the realistic limit of life and reliability. The motor can draw 10 times the continuously rated current provided it does not exceed its insulation temperature rating. Various NEMA motor ratings include specifications for starting torque. For example, the spec allows starting torque to be as much as 225% of running torque, and provides ratings for the allowable number of starts per hour. This is when the motor insulation experiences the most stress.
关于典型伺服系统的寿命和可靠性的主要限制因素是它产生的热量。通风良好的环境是必要的，并且在某些情况下，添加冷却风扇以帮助循环空气。
但这对连接到固态起动器，可变频率驱动器或伺服驱动器的电机不保持真实。这是由于IGBT和FET固态开关装置的电流承载能力有限。峰值电流能力通常为200至300％的连续，并且通过必须遵循的时间斜坡（DI / DT）进一步限制，或者设备将失败。当电动机连接到驱动器，固态启动器或伺服放大器时，电机的扭矩和电流仅限于该固态装置的电流额定值（DI / DT）。
固态，控制伺服电机的高功率开关装置具有最大电流限制以及在每单位时间的电流安培中测量的上升率，通常是每毫秒的安培。
These three triangles show the standard relationship between time, torque, and inertia and then how they are modified with changes in insulation materials or the addition of gears for speed reduction.
Gasoline vs. electric motors
The same horsepower-rating problem shows up when accelerating a car from zero speed. A 3246-lb Corvette may require 424 ft-lb (430 hp at 5900 rpm) to reach 60 mph in 3.91 seconds, but it may require only two to five hp to keep it running at 65 mph on level ground. That’s why some newer SUVs have a provision to shut down the operation of some of their cylinders in cruise mode, dramatically reducing fuel consumption.
Compare this to an electric car— a mobile, mechatronic system. What other kind of motor and drive system can provide low speed at high torque and high speed at low torque from the same set of hardware?
Understanding the work to be performed helps us understand the demands on the power source as well. The ideal power source must release high current for starting torque to accelerate a car. Lead-acid batteries do not fare well, even when disregarding the 1800 lb of battery packs needed to move the car. When compared to the amount of energy stored in a gallon of gasoline, it is easy to understand why we are still using it.
Solutions do exist
One solution to the drive problem is to control the motor’s field winding. Field-oriented control in an ac inverter is similar to setting the ignition timing on an internal combustion engine. By advancing and retarding the switching time of the power control transistors, it is possible to double the torque of the ac motor for a time. In an electric car, this is sometimes referred to as an “electronic, two-speed transmission” and eliminates the need for a mechanical transmission.
在调整电机应用时，考虑其旨在执行操作的完整循环。考虑占空比（准时与OFF-TIME），应用的起始和停止条件 - 特别是高惯性和高摩擦负载 - 作为电机完成的工作的一部分。在许多应用中，较小的，更高的RPM电机可能会更具成本效益。这些因素还有助于指导技术选择，即，哪种类型的电机最适合应用？
Solid Technologies
提起：Motion control • motor controls那Mechatronics
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