retrofit on EMCO PC turn 55
As I said, you can run a 5-wire motor on any drive. On a bipolar drive you ignore the centre tap wire and leave it unconnected. On a unipolar drive, it is the 0v return wire.
Isn't that going to double the impedance of the coil (two coils in series, rather than one)? Wouldn't you have to increase the voltage by sqrt(2) to get the same power out of it?
I seems like in order to have it behave according to the original specs, you would do just what you said, but ground the center tap.
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Yes, and possibly no.
Isn't that going to double the impedance of the coil (two coils in series, rather than one)? Wouldn't you have to increase the voltage by sqrt(2) to get the same power out of it?On a bipolar drive you ignore the centre tap
You have two coils in series, so the impedence (and inductance) is higher. But you are energising both sides of the winding, not just half of it, so the magnetic flux is doubled.
Quite how that translates to torque and power for a particular motor I am not entirely sure. Looking at this datasheet for reconfigurable stepper:
www.slidesandballscrews.com/pdf/stepperm...SY60STH88-3008BF.pdf
It seems that, compared to unipolar use, the holding torque is higher wired bipolar series (you can't do bipolar parallel with a 5-wire) and the inductance is higher. The increased induction might limit the motor speed at a given voltage, if the machine does not hit physical limits first.
HOWEVER! I have just noticed that, contrary to the article I first linked to, it is not possible to run a 5-wire motor with a Gecko G540.
There is more information here, including suggestions that it might be a simple modification to allow the motors to run with Geckos.
(That will teach me not to allow something I read on the Interwebs to over-ride my original opinion)
This only matters if you decide to swap the drives, though.
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HOWEVER! I have just noticed that, contrary to the article I first linked to, it is not possible to run a 5-wire motor with a Gecko G540.
There is more information here, including suggestions that it might be a simple modification to allow the motors to run with Geckos.
(That will teach me not to allow something I read on the Interwebs to over-ride my original opinion)
This only matters if you decide to swap the drives, though.
Where did you read this? If I were to construct a driver in the simplest way I can imagine, it would also drive a 5-wire motor.
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Where did you read this?
It isn't in the Rev 8 manual (interestingly)
But: www.geckodrive.com/gecko/images/cms_file...%20MANUAL%20REV1.pdf
"1) MOTORS: One to four step motors are required. All NEMA-17, many NEMA-23 and a few NEMA-34 motors are
acceptable. The motors preferably should be square in cross-section, not round. The motors can be 4, 6 or 8-wire
motors. 5-wire motors cannot be used with the G540. Choose a motor that has a rated current of 3.5A or less.
Choose a motor that has a rated winding inductance of 2.5mH to 3mH if maximum power output (>100W mechanical)
is a requirement. Never use a power supply voltage greater than 32 times the square-root of the motor inductance
expressed in milli-Henries (mH)."
It might be something that would need to be checked with Gecko, as they have changed the drives since that document was written.
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jrkeat wrote:
Where did you read this?
It isn't in the Rev 8 manual (interestingly)
But: www.geckodrive.com/gecko/images/cms_file...%20MANUAL%20REV1.pdf
"1) MOTORS: One to four step motors are required. All NEMA-17, many NEMA-23 and a few NEMA-34 motors are
acceptable. The motors preferably should be square in cross-section, not round. The motors can be 4, 6 or 8-wire
motors. 5-wire motors cannot be used with the G540. Choose a motor that has a rated current of 3.5A or less.
Choose a motor that has a rated winding inductance of 2.5mH to 3mH if maximum power output (>100W mechanical)
is a requirement. Never use a power supply voltage greater than 32 times the square-root of the motor inductance
expressed in milli-Henries (mH)."
It might be something that would need to be checked with Gecko, as they have changed the drives since that document was written.
It would probably be easy to convert the motors to be 6 wire--I'll see when they get here.
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There is a terminal block in the back of the motor with 10 terminals. 5 of the terminals are tied together (and there is no connection wire on the common bus). The other 5 terminals have wires connected to them.
On the motor side of the terminal block there are 10 wires connected to 10 terminals on the stator coils. This seems to indicate there are 5 indiviual coils and one side of each coil is common.
I will leave it up to you guys to decide if this motor can be converted to a useable configuration. Personally I don't think so.
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This seems to indicate there are 5 indiviual coils and one side of each coil is common.
Ah that _is_ interesting and might indicate that these are 5-phase stepper motors. Apparently they are quite nice and rather smooth.
Stepgen types 11 to 14 are for 5-phase stepper motors. However, that just drives 5 output bits, which is only part of the answer as you still need the current-control PWM.
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Note that a dissasembed step motor is usually destroyed by dissasembly
(if the rotor is removed)
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I thought my old motors went out in the scrap but it turns out I still have them. One is fully disassembled and the other just has the back off.
There is a terminal block in the back of the motor with 10 terminals. 5 of the terminals are tied together (and there is no connection wire on the common bus). The other 5 terminals have wires connected to them.
On the motor side of the terminal block there are 10 wires connected to 10 terminals on the stator coils. This seems to indicate there are 5 indiviual coils and one side of each coil is common.
I will leave it up to you guys to decide if this motor can be converted to a useable configuration. Personally I don't think so.
Thanks for the info!
They're still useable, but cuts off the simplest solutions. (5 phase stepper controllers exist, but are much harder to find--the Techno Drive KR-5M is available on Ebay right now). If the manufacturers' claims are to be believed, there are many advantages to the 5-phase motors: www.orientalmotor.com/technology/articles/2phase-v-5phase.html --lower vibration, higher precision, etc.
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Sounds like a 5 phase step motor in star configuration
Note that a dissasembed step motor is usually destroyed by dissasembly
(if the rotor is removed)
It doesn't look like I'll have to disassemble anything--it up to me to decide if I want to drive a 5-phase or not. (Or get the existing electronics to do it.)
Out of curiosity, how does disassembly destroy the motor?
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