Electric motors and drives
Electric motors and drives
(OP)
Greetings,
I am a mechanical engineer with limited knowledge of electrical equipment. I need to know what is a drive that should be used with the motor I am getting on a pump. I have never seen a drive! What does it do?
Thanks.
I am a mechanical engineer with limited knowledge of electrical equipment. I need to know what is a drive that should be used with the motor I am getting on a pump. I have never seen a drive! What does it do?
Thanks.





RE: Electric motors and drives
But, these days it is usually about a frequency inverter feeding an asynchroous motor aka induction motor. Some people make a difference between the motor and the frequency inverter and then the word "drive" is used for the frequency inverter.
My guess is, in your case, that "drive" means a standard frequency inverter.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Electric motors and drives
It converts fixed frequency mains voltage (60 Hz or 50 Hz, depending on where in the World you are) to a variable frequency and voltage needed to make the motor turn at variable speed. A crude equivalent could be the classical belt variator. Only, the frequency inverter has a much larger speed range and a much better efficiency. And it needs next to no maintenance. A frequency inverter is also often referred to as "a VFD" where VFD stands for Variable Frequency Drive.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Electric motors and drives
One use of a drive is to lower the starting current on a large motor. For a pump a soft start is cheaper and will usually do the job.
A second use for a drive on a pump is to control the flow by varying the speed of the pump. This implementation is used instead of a flow control valve or in addition to a flow control valve.
In many plants a drive used to reduce the starting current would be the responsibility of the electrical department. A drive used to control flow would be either under the jurisdiction of the instrument department or a joint responsibility of both departments. The instrument department would have responsibility and control of the PID settings.
Bill
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"Why not the best?"
Jimmy Carter
RE: Electric motors and drives
Thanks
RE: Electric motors and drives
Briefly;
Direct On Line starting. > Cheapest, draws up to 800% of rated running current when starting. The number of starts per hour is limited by internal motor heating. Although the starting current is less, the starting time is longer.
Soft start.> More expensive than DOL. This limits the starting current to a value that you select. Possibly 200% or 300%. The number of starts per hour is still limited by motor heating.
VFD. > Most expensive. This has the advantage of efficient speed control as well as efficiently reducing starting current. Motor heating during starting is minimal and there may be no limit on the number of starts per hour in some applications.
For more detailed information start searching.
Bill
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"Why not the best?"
Jimmy Carter