Articles in this category explain essentials about electric motors, mainly related to variable speed applications along with VFDs.
Considerations about motor noise level This post provides few considerations about motor noise level with respect to inverter supply. Noise might be considered as one performance criteria of the motor. Noise level of electric equipment is regulated by standards and regulations, often involving local law. Depending on the maximum level, Read more…
What type of asynchronous motor suits the best for VFD duty? Asynchronous motor is sometimes called the work horse of the industry. And this nickname is well earned. It is because millions of such motors are utilized in different applications across the globe. They help the world turning. While most Read more…
Are surge arresters suitable for protection of VFD fed motors? Surge arresters are commonly used to protect electric equipment against excessive overvoltages. At the same time, many voltage source inverters produce non-sinusoidal voltages that stress the machine insulation. Thus, one could ask whether surge arresters are suitable means to protect Read more…
Finding an optimum field weakening point Motors supplied from variable frequency drives (VFD) have the freedom to set the field weakening point almost arbitrarily. By doing that you can optimize the drive system. The message of this article is how to find an optimum field weakening point. Let’s start with Read more…
Variable Speed Motors – Which type suits the best? Electric variable speed drive system consists as minimum of a VFD and an electric motor. So the question is: Which motor type suits the best for variable speed control? As usual, the answer depends on multiple factors. Among those factors belong Read more…
KYDS: Know Your Drive System KYDS -Know Your Drive System – is our new program where you learn more about variable speed drive system and the most important system components (transformer, VFD, electric motor, cooling system, harmonic filter). Scope of KYDS The scope of the Know Your Drive System program Read more…
Challenges of high-speed machine design In turbomachinery applications the conventional solution is a 4-pole machine with nominal speed in the range 1’500 – 2’000 rpm and a speed-increasing gear. However, the alternative is a gearless high-speed drive. Such concept may offer several advantages (compact design with small footprint, absence of Read more…
Torque-Speed characteristic of induction machine This post aims to explain the famous torque-speed characteristics of asynchronous (induction) motor. We try to make it simple and understandable. First we thought to put without mathematics into the title. Well, we might write 2-3 formulas, but keep it as simple as possible. Promised! Read more…
Confused about motor nameplate voltage? Have you ever observed the difference between power system voltage and motor nameplate voltage in North American region? One can get easily confused seeing that the nameplate voltage of the machine does not fit the supply voltage. For AC industrial motors it is a common Read more…
Dealing with critical speeds This post explains some basic considerations related to variable speed motors and their critical speeds. The fact that motor operates at variable speed makes it more challenging from rotordynamic perspective in order to avoid critical speeds within the operation speed range. At the same time, VFDs Read more…