Converting the operating voltage of an Enduro servo motor

[johnnydb]

1 minute ago, Northmount said:

Many motors have been damaged due to under voltage.  They run hot, have low power output, run slow, cooling fans not as effective due to running slow, etc.  Depends on your definition of "fry".  As motor winding insulation breaks down due to running hotter than design, internal shorts may occur, and your motor could "fry". 

If you only use the motor on lower than design voltage for a few minutes now and then, like many hobbyists, you may get away with few problems, just slow and weak output.

And what you are saying is also possible...I'd like to see the faceplate on the motor itself state that it can handle the different voltages. It's probably written in electrical speak...but it will state it. 

And what you are talking about is called "single phasing" and definitely burns up three phase motors.  If there isn't enough voltage to push the current through a coil it definitely will run hot and do as you say by burning up the insulation on the motor windings. 

[Northmount]

2 minutes ago, johnnydb said:

So if a motor will use 5amps at 240V it will draw 10 amps at 120V (as stated previously) 

That is incorrect.  The previous discussion neglected back emf that limits running current, usually approximately 1/7 of the starting current which is mostly limited only by the resistance (copper losses) of the windings.  A simple resistor circuit will not agree with your statement that it would draw more current at a lower voltage.

[Northmount]

2 minutes ago, johnnydb said:

And what you are talking about is called "single phasing" and definitely burns up three phase motors.

Happens on single phase motors too.  Yes it is worse when 3 phase motors run single phase, but that is not the same as a single phase motor running at 50% voltage.

 

[johnnydb]

19 minutes ago, Northmount said:

That is incorrect.  The previous discussion neglected back emf that limits running current, usually approximately 1/7 of the starting current which is mostly limited only by the resistance (copper losses) of the windings.  A simple resistor circuit will not agree with your statement that it would draw more current at a lower voltage.

Woah...

Inductive resistance is offset by the run capacitor...but a 3hp motor will not use less watts because of a lower voltage.  It must use the same. A Delta wired motor is a Delta wired motor...the only thing that changes is the taps for the coils. And if there isn't enough voltage to push through the coils (because the taps didn't change) it will sit there and Humm and get hot. And if for some reason half of the coils don't get used...then it might run but it will be "single phased" and burn up quickly. 

And even though only one phase drops out on a three phase motor it's still termed single phasing by those of us coming in to replace the motor. 

And there are a bunch of motors running around that can take either voltage...just a different set of contacts in the pecker head that you wire into. Most commonly seen in the pump motors for residential pools. 

Edited October 27, 2021 by johnnydb
Technical edit

[Northmount]

53 minutes ago, johnnydb said:

Woah...

Inductive resistance is offset by the run capacitor...but a 3hp motor will not use less watts because of a lower voltage.  It must use the same. A Delta wired motor is a Delta wired motor...the only thing that changes is the taps for the coils. And if there isn't enough voltage to push through the coils (because the taps didn't change) it will sit there and Humm and get hot. And if for some reason half of the coils don't get used...then it might run but it will be "single phased" and burn up quickly. 

And even though only one phase drops out on a three phase motor it's still termed single phasing by those of us coming in to replace the motor. 

And there are a bunch of motors running around that can take either voltage...just a different set of contacts in the pecker head that you wire into. Most commonly seen in the pump motors for residential pools. 

You are confusing things by introducing 3 phase motors in a subject that is single phase servo motors.  You see to be confusing starting/run windings with 3 phase as well.  So throw all that stuff out of this discussion.

These servos being discussed here are not being rewired to different voltage supplies at the motor.  Hence those comments in your assertions are not valid. The difference is in the circuitry of the PC control boards, which have different part numbers for the different voltage supplies.  These are not simple induction motors.

You also appear to be assuming the motor has the same HP output at the lower voltage.  I agree to some extent that the current drawn by the motor when attached to 110 versus 220 VAC (with no other wiring changes) may tend to be greater during the starting cycle, but not at the instant the switch is thrown.   Also depends on the attached load.  If I put 2 pole induction motor on a variable auto transformer with no attached load, it will run at rated speed around 40-50 VAC.  And the current draw is low.  (Doesn't start as fast either.)  You can see the current demand decrease due to the back emf as the motor speed increases.   As you apply load, the current draw increases to match the load.  All standard stuff and logic.

Further more, these digital sewing machine servo motors do not operate the same as simple induction motors.  Simply stated, the electronics pulses the field (stator) windings as needed to run the motor at the speed demanded by the operator.  (There is more to it than that, but let's keep it simple.)  If there is a low load demand (HP), the pulse is of shorter duration.  So a 220 VAC setup, may run adequately (depending on the electronics design) on 110 VAC.  But you are not going to get the same performance, nor top end speed and power.

[Northmount]

1 hour ago, johnnydb said:

And even though only one phase drops out on a three phase motor it's still termed single phasing by those of us coming in to replace the motor.

Simple delta wired motor, cut off 1 phase connection and you lose power to 2 phases, so it truly is single phasing.  Draw yourself a simple diagram and count the number of phases that receive power.  It will become obvious.

[johnnydb]

8 hours ago, Northmount said:

You are confusing things by introducing 3 phase motors in a subject that is single phase servo motors.  You see to be confusing starting/run windings with 3 phase as well.  So throw all that stuff out of this discussion.

These servos being discussed here are not being rewired to different voltage supplies at the motor.  Hence those comments in your assertions are not valid. The difference is in the circuitry of the PC control boards, which have different part numbers for the different voltage supplies.  These are not simple induction motors.

You also appear to be assuming the motor has the same HP output at the lower voltage.  I agree to some extent that the current drawn by the motor when attached to 110 versus 220 VAC (with no other wiring changes) may tend to be greater during the starting cycle, but not at the instant the switch is thrown.   Also depends on the attached load.  If I put 2 pole induction motor on a variable auto transformer with no attached load, it will run at rated speed around 40-50 VAC.  And the current draw is low.  (Doesn't start as fast either.)  You can see the current demand decrease due to the back emf as the motor speed increases.   As you apply load, the current draw increases to match the load.  All standard stuff and logic.

Further more, these digital sewing machine servo motors do not operate the same as simple induction motors.  Simply stated, the electronics pulses the field (stator) windings as needed to run the motor at the speed demanded by the operator.  (There is more to it than that, but let's keep it simple.)  If there is a low load demand (HP), the pulse is of shorter duration.  So a 220 VAC setup, may run adequately (depending on the electronics design) on 110 VAC.  But you are not going to get the same performance, nor top end speed and power.

From what I was reading up on...these actually go by another name when I was learning this stuff....and probably because I am a primadonna at work everyone went along with the monkey who knew what to do. 

 

So these servo motors are just lower voltage three phase motors controlled by a PBM which has something akin to a "magic ballast" that can utilize a variety of voltages up to a point because the SCRs (type of transistor) are going to only pulse out so much juice after the power is first being turned into DC then turned into the three phase AC by the pulsing SCRs needed to drive the motor in a precise proscribed manner. 

Usually we use a VFD to do such things for the squirrel cage three phase rated for such...but these are a bit different as they are more for precise positioning of the armature... like I said....these I know by a different name...stepper motor is what I Know these by. 

Now what I do know is that these motors will not have the same torque if they don't have enough voltage to create the DC voltage high enough with enough amps. Most of the voltage is erased by the rectifier anyway. 

Meaning yes they will turn not under load but they will bog down quickly on the thicker leathers. They simply won't have the watts to power it all.  

Personally I would stick to the rated voltage. 

 

[kgg]

Basically for me the question really is whether this motor is an AC servo motor or a DC servo motor as that really will determine the effect of putting half the input voltage on the motors controller board.

kgg

Edited October 28, 2021 by kgg
missing word

[johnnydb]

3 hours ago, kgg said:

Basically for me the question really is whether this motor is an AC servo motor or a DC servo motor as that really will determine the effect of putting half the input voltage on the motors controller board.

kgg

A DC servo motor are usually those on RC cars and airplanes... sometimes toy robots too. They have permanent magnets. Not a lot of power or torque to them. And usually DC servo motors don't actually turn a full 360⁰. They turn 180⁰ at most. 

AC servo motors are actually what we call Stepper Motors. They are usually three phase motors (internally but can be more phases depending on size...I've seen 12 phases but didn't have to do anything with it) 

All the electricity fed into them is first turned into DC current by electronics and then transformed again into AC by electronics to carefully and precisely control the position of the armature. (As determined by a sensor) They are the only ones that will have the torque necessary to sew leather.  So... you most likely have a stepper motor. 

The input voltage needed is determined by the specs...it can be a wide range. So long as you don't fry the diodes for the rectifier you are gold.  

Now the electronics controlling everything are usually powered by the initial power coming into the device. Tapped right off the cord almost. Look for a different colored terminal or markings to determine which is the hot, neutral, ground, and/or other hot. 

[Northmount]

On 10/28/2021 at 8:20 AM, johnnydb said:

A DC servo motor are usually those on RC cars and airplanes... sometimes toy robots too. They have permanent magnets. Not a lot of power or torque to them. And usually DC servo motors don't actually turn a full 360⁰. They turn 180⁰ at most. 

AC servo motors are actually what we call Stepper Motors. They are usually three phase motors (internally but can be more phases depending on size...I've seen 12 phases but didn't have to do anything with it) 

All the electricity fed into them is first turned into DC current by electronics and then transformed again into AC by electronics to carefully and precisely control the position of the armature. (As determined by a sensor) They are the only ones that will have the torque necessary to sew leather.  So... you most likely have a stepper motor. 

The input voltage needed is determined by the specs...it can be a wide range. So long as you don't fry the diodes for the rectifier you are gold.  

Now the electronics controlling everything are usually powered by the initial power coming into the device. Tapped right off the cord almost. Look for a different colored terminal or markings to determine which is the hot, neutral, ground, and/or other hot. 

Don't forget brush type with a potentiometer versus digital.  Both are used on leather sewing machines.