DC motors are usually seen in applications where the motor speed needs to be externally controlled. AC motors work best in applications where power performance is sought for extended periods of time. All DC motors are single phase, but AC motors can be single phase or three phase.
AC and DC motors use the same principle of using an armature winding and magnetic field except with DC motors, the armature rotates while the magnetic field doesn’t rotate. In AC motors the armature does not rotate and the magnetic field continuously rotates.
In some applications today, DC electric motors are replaced by combining an AC electric motor with an electronic speed controller, known as variable frequency drives. DC electric motors are replaced with an AC electric motor and an electronic speed controller because it is a more economical and less expensive solution.
DC electric motors have many moving parts that are expensive to replace, and DC electric motor repair is usually more expensive than using a new AC electric motor with an electronic controller.
In our experience, combining an AC motor and drive proves to be the most cost effective solution for mostapplications. When servicing our customers in the field, we often recommend looking at the SMVector Series Variable Frequency Drive in combination with a three phase AC motor.
Answer:
C
Explanation:
This is what I put on my test, but I'm not sure if it's correct.
Translate percentages to letter grades. I know this from personal experience.
Answer:
Getting into a great college program
Explanation:
Getting into a great college program is a perfect example of a long term goal if you are in middle school now. A long term goal is a goal that you will want achieve in the far future (like 2, 3, 4 years, and so on), and getting into a great college program is an example of a long-term goal. Long-term goals usually take years to accomplish.
However, If you are in a middle school now, then you should set a goal of getting into a great college program because it will take years to achieve this goal.
A Long-term goal is a goal that a person has in mind to achieve in the future and they are important if you aim to build a successful career. Long term goals need better planning because they are goals you cannot accompany in a short while; they take several years to be achieved.
