10-04-2017, 08:32 PM
AC drive
[attachment=16171]
The word "drive" is used loosely in the industry. It seems that people involved primarily in the world of gear boxes and pulleys refer to any collection of mechanical and electro-mechanical components, which when connected together will move a load, as a "drive". When speaking to these people, an AC drive may be considered by them as the variable frequency inverter and motor combination. It may even include the motor's pulley - I am not sure.
People in the electrical field and electrical suppliers usually refer to a variable frequency inverter unit alone, or an SCR power module alone (when discussing DC drives) as the "drive" and the motor as the "motor".
Manufacturers of variable frequency drives (VFD) used to refer to the drive as just that, a "variable frequency drive". More manufacturers are referring to their drive as an "adjustable speed AC drive". To make matters worse when a motor is included in the package it may be referred to as an "adjustable speed AC drive system".
A little about AC drives
The main power components of an AC drive, have to be able to supply the required level of current and voltage in a form the motor can use. The controls have to be able to provide the user with necessary adjustments such as minimum and maximum speed settings, so that the drive can be adapted to the user's process. Spare parts have to be available and the repair manual has to be readable. It's nice if the drive can shut itself down when detecting either an internal or an external problem. It's also nice if the drive components are all packaged in a single enclosure to aid in installation but that's about it.
Ambiguous Motor Theory
The real action in an AC variable frequency drive system is in the motor. This is really where it all happens.
To be an AC drive application Wizard (which is several levels higher then Guru) one must understand how motors use electric power. It is essential. I cannot emphasize the importance of this.
A Side Note About Fishing, Electro-magnets, Current, and Magnetic Conductivity
When we go fishing we put bait on a hook and throw it in water knowing that according to generally accepted theory, a hungry fish will sooner or later, bite. Well the truth is we don't know why the fish bite. No one to date, has talked to a fish (well maybe a few people talk to fish). The fact the we get hungry and therefore fish must too, seems like a safe assumption. But it doesn't really matter because we do know that putting bait on a hook will get fish into the boat.