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[Newbie] Open Loop VFD For Vector Motor

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Susan_in_SF

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#1
I am into vintage machinery, but want to convert several of my machines so that I can use a vfd to control speed and torque. I have been very fortunate in finding unusually great deals on both inverter duty and vector duty motors. For example, today an ebay seller accepted my $40 offer (with $26 shipping) for a 1.5 hp vector motor. Maybe I should not have bought these vector motors before having a definite answer regarding if they were compatible with open loop vfd's. I am a newbie at this, and I am pretty sure I don't need the precision (or headache of learning) of encoders for closed loop vfd's. Maybe there is no such thing as open or closed loop vfd's, and open and closed systems and are just referring to the use of encoders. My 2 hp vector duty motor came with an encoder on it. Btw, i am posting my question here after I searched all over google only to not find a definite answer. Thank you for any helpful info you may be able to offer :)
 

mksj

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#2
Assuming this is a 3 phase motor, a vector motor is typically an inverter motor with an attached encoder for a closed loop feedback. The encoder is on a short stub shaft at the back of the motor, the encoder can be removed if not used. The encoder is used more for exact shaft positioning, speed accuracy and holding in a stop position to prevent creep of the attached system. So no problem with using a vector motor in an open loop or what is commonly referred to as sensorless vector control. Vector type motors also carry full Hp ratings to 2X their base speed and often to their top speed which can be around 3X their base speed. Running in sensorless vector mode, they will have tighter low speed control and typically RPM can be held to within 0.1%. Just make sure you get a decent VFD to go with this type of motor.
 

Susan_in_SF

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#3
Assuming this is a 3 phase motor, a vector motor is typically an inverter motor with an attached encoder for a closed loop feedback. The encoder is on a short stub shaft at the back of the motor, the encoder can be removed if not used. The encoder is used more for exact shaft positioning, speed accuracy and holding in a stop position to prevent creep of the attached system. So no problem with using a vector motor in an open loop or what is commonly referred to as sensorless vector control. Vector type motors also carry full Hp ratings to 2X their base speed and often to their top speed which can be around 3X their base speed. Running in sensorless vector mode, they will have tighter low speed control and typically RPM can be held to within 0.1%. Just make sure you get a decent VFD to go with this type of motor.
Thank you MKSJ :)
 

strantor

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#4
What kind of VFD are you using? If it has closed loop capability, and your motor already has an encoder, why not use it? There isn't much to learn. If it doesn't have encoder feedback, but has sensorless vector, use that. Much better speed regulation than V/F. If it's just a basic V/F drive, no problem. Using a vector motor with a V/F drive is a bit like using a thoroughbred to plow, but it will still plow. And if you don't use the encoder, you can take it off and sell it on eBay for probably as much as you bought the motor for.

P.s. "vector" motor means different things to different people. To Baldor, last I checked, "vector motor" is a motor with a separate cooling blower, which makes it a rockstar for running extended periods at low RPM & high torque. If your motor has a blower on it, she's a keeper.
 

Susan_in_SF

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#5
Strantor,
Wow. A lot of this stuff I need to double check before I can reply. I have been sick, and am just finally upright. I will post pics and what I find within next couple of days. I appreciate your help :)
Susan
 
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