# Servo motors



## iaov (Apr 14, 2008)

Hi all. Have been dealing with servo motors and servo drives lately and I do not have much experience with them. Have worked on large DC motors and drives and AC 3p motors and drives for many years. Any body have any experience with servos?? Can you tell me anything about them??Thanks.


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## McClary’s Electrical (Feb 21, 2009)

iaov said:


> Hi all. Have been dealing with servo motors and servo drives lately and I do not have much experience with them. Have worked on large DC motors and drives and AC 3p motors and drives for many years. Any body have any experience with servos?? Can you tell me anything about them??Thanks.


 


I'm certainly no expert, but have dealt with a few. Servo motors are used when the position of the motor needs to be trackable and programmable. They are very long so they can produce torque quickly, rather than needing to gain momentum. Most servos are long and narrow.


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## John (Jan 22, 2007)

mcclary's electrical said:


> I'm certainly no expert, but have dealt with a few. Servo motors are used when the position of the motor needs to be trackable and programmable. They are very long so they can produce torque quickly, rather than needing to gain momentum. Most servos are long and narrow.


Size depends on motor type. A 1KW ~1 Hp AC servo motor is smaller in size than a 1 HP AC 3 phase motor.


iaov what's the application? I have delt with a lot of servo motors attached to CNC machines.


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## McClary’s Electrical (Feb 21, 2009)

John said:


> Size depends on motor type. A 1KW ~1 Hp AC servo motor is smaller in size than a 1 HP AC 3 phase motor.
> 
> 
> iaov what's the application? I have delt with a lot of servo motors attached to CNC machines.


 


That's kind of what I meant, they are always smaller in diameter, and the more torque you need, the longer the motor gets. I've worked on servos 6 ft. long


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## John Valdes (May 17, 2007)

Servo motors can be AC or DC. Both types usually use a resolver for precise operation. Sometimes encoders are used.
Servos are are theoretically identical to either an AC induction or DC motor. 

An example would be a motor needs to drive a conveyor belt to point "B" from point "A". Then back to point "A". A regular motor would require limit switches and a reversing contactor to accomplish this task. A servo motor can be programmed to do this independently.

The parameters are entered into the controller. The servo motor advances at the preset speed to point "B". It must know its at point "A" as a reference point. The resolver sends a feedback signal to the controller. This signal tells the controller exactly what position the servo shaft is at. It then counts revolutions and determines when it is at point "B". Then it reverses the servo motor and counts its way back to point "A". This can be done at very fast speeds for automation.
This is a very basic explanation of a two axis servo control. Hope it made sense.


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## iaov (Apr 14, 2008)

John said:


> Size depends on motor type. A 1KW ~1 Hp AC servo motor is smaller in size than a 1 HP AC 3 phase motor.
> 
> 
> iaov what's the application? I have delt with a lot of servo motors attached to CNC machines.


 Many different apps, none of wich are CNC. Mostly food/cheese handling equip. I have been sucsessfull so far finding problems but know from experience that one of these days it will require me realy knowing and understanding what is actually happening inside these motors.


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## John Valdes (May 17, 2007)

iaov said:


> Many different apps, none of wich are CNC. Mostly food/cheese handling equip. I have been sucsessfull so far finding problems but know from experience that one of these days it will require me realy knowing and understanding what is actually happening inside these motors.



Servo motors and controls are a specialized field. Motor shops send this equipment off in most every case. I would not get to concerned as you just need to have replacement parts and motors. And help!
Whatever you do, do not take a servo motor apart unless you understand how to set the resolver.
I know guys that spent many hours of class time on servo and still struggle. The biggest issue is the marked differences between manufacturers. The best servo repair shops have records of every single servo they have ever worked on for reference and instructions over many years.
This is by no means a technology you learn in a few weeks or even a few years. Practice makes perfect as they say. And it seems you have much practice in store for you.

I would find a good servo shop and get to know them. Better now than during a breakdown.


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## MDShunk (Jan 7, 2007)

iaov said:


> Many different apps, none of wich are CNC. Mostly food/cheese handling equip. I have been sucsessfull so far finding problems but know from experience that one of these days it will require me realy knowing and understanding what is actually happening inside these motors.


iaov, are you a Schreiber-ite or Schriberian or whatever they call themselves? If that's the case, 99% of your servo failures are going to be from water inside. :laughing:


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## iaov (Apr 14, 2008)

Hey MDSUNK.. I haven't a clue as to what a Shrieberite is but I'm certain I've been called worse before.:laughing: I can certainly attest to the fact that everything in a cheese plant becomes soaked and water logged eventually.


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## JohnR (Apr 12, 2010)

MD, come clean, what is that? I tried to look it up but couldn't find anything that looked right.


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## MDShunk (Jan 7, 2007)

JohnR said:


> MD, come clean, what is that? I tried to look it up but couldn't find anything that looked right.


Wisconson, where he is from, is headquarters to the world's largest cheese and dairy manufacturer. They have plants all over the world. Probably dozens in the US alone.


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