Wiring an 8 lead stepper to a Gecko 201

[ChrisJ]

I need to confirm how to wire an 8 lead stepper motor to the Gecko, assuming that there only one way to wire it.

My guess is that motor winding A and A* are wired to terminals Phase A & Phase B in parallel and motor windings B and B* are wired to terminals Phase C and D in parallel. Is this correct?

Guidance is greatly appreciated.
Chris

[CJL5585]

That is correct if you want to wire the steppers in bi-polar parallel.

Normally the A and A*, B and B* are used to identify wiring in the uni-polar mode.

Whether the steppers are wired in bi-polar parallel or bi-polar series in my opinion depends upon the power supply voltage and current ratings of your driver supply.

Not knowing what your power supply ratings are, I will give you the "Rule of Thumb" that I use.

Power supply voltage 24 Volts with sufficient current: Bi-polar Parallel
Power supply voltage greater than 30 Volts: Bi-polar Series

Hope this helps.

Visit the Gecko site and download the manual for the 201 series of drives. It will give you diagrams.

Jerry

[ChrisJ]

I looked only at the G201 manual. I should have looked further. I now see the motor hookup PDF.

Well, I have 65V power. I was planning on wiring it up in parallel to maximize on power. Stepper is 1076 oz-in (holding torque) in bipolar configuration. 6.4 amp rated phase current.

One more question. The Gecko G201 indicates a need to add a resistor across the current set terminals. If this motor has a 6.4 amp rated phase current, the maximum voltage for the motor is 140 volt, and I will be supplying 65 volts to the G201, how do I determine the amp draw so that I can size the resistor? I am not sure what voltage the 6.4 amp rated phase current was listed at (140V ?).

Thank you for your response.
Chris

[CJL5585]

I have wired many Gecko 201's with 48 Volt supplies.

The problem with running steppers in bi-polar parallel at high voltages is heat generated in the motor windings. On my motors, which are Superior Electric the charts show that the torque is the same for both series and parallel wired configuration at a voltage of 60 Volts. I believe this is true with most steppers.

Personally, with a 65 volt supply voltage, I would install a 47K Ohm resistor which if I remember correctly would allow about 5 or 6 amps. The main thing is to make sure each + 65 Volt drive line is fused at 5 Amps with a 250 Volt fast blow fuse. That way, if any overcurrent conditions occur your drives will be protected. I would also have the steppers wired in bi-polar series mode, otherwise you will only be able to run them for a very short time due to overheating. They would most likely give you 3rd degree burns if you touched them wired in bi-polar parallel at 65 Volts after a short period of operation and would most likely shorten the motor life.

Also, none of the drives or motors that I have wired per above have ever experienced a failure, which is a good indicator of being correctly wired.

Hope this helps,
Jerry

[ger21]

In most cases, bipolar parallel will give much higher torque at higher speeds. When wired bipolar series, torque usually falls off at a much higher rate. Mariss from Gecko recommends running between 10 and 20 times the motors rated voltage.

I've heard that the best voltage to use is the lowest voltage that will give you the performance your trying to achieve. This will keep the motors as cool as possible.

[ChrisJ]

Thank you both for your responses.

I was trying to remember where I saw the increased power/torque information and found it again. It was one of Gecko's white papers, titled "Motor Power Basics". It describes what I mentioned earlier, more power and what Gerry just mentioned, maintains the torque at higher RPMS.

I guess I am a little confused by Gecko's recommendation of 10 to 20 times motor rated voltage. My stepper motor is rated for a maximum voltage of 140, but this is the only rating given in the cut sheet. This can't possibly be the rated voltage that Gecko is refering to can it? If not, how do I find out the rated voltage so I can see if the 65 volt that I will be supplying falls in the 10 to 20 times range that Gecko recommends?

The application is for a 8" rotary table where the motor will be direct coupled. Most likely either method of wiring sounds like it will be sufficient since I will not be indexing this table at the high end of the stepper motors RPM. I will most likely limit it to 450 RPM. With a 90to1 gear ratio this would index the table at 5 revs/min. Probably shouldn't go any higher than that.
It is always nicer to have more power though, but I sure don't want to over heat the motor.

Chris

[ViperTX]

Usually most steppers have low voltage coils.....therefore the 10X......with your stepper stick with the 65 volts and use the appropriate current limit resistor.

[ger21]

If you know the motors rated current and resistance, multiply them together to get the voltage.

[ChrisJ]

Now that is too simply and straight forward.

O.K.
Phase Resistance is 0.5ohms
Rated phase current is 6.4 amps

So rated voltage is 3.2 volts

If I use the 20X rule, that gets me 64 volts. So at 65 volts I am right at the suggested limit by Gecko.

Chris

[ViperTX]

Originally Posted by ChrisJ Now that is too simply and straight forward. O.K. Phase Resistance is 0.5ohms Rated phase current is 6.4 amps So rated voltage is 3.2 volts If I use the 20X rule, that gets me 64 volts. So at 65 volts I am right at the suggested limit by Gecko. Chris

Didn't you originally say that these were 140 volt steppers???

[ChrisJ]

Yes.

The cut sheet states that the maximum voltage is 140V.

I was asking how to apply the 10x/20x rule to the stepper motor and needed a rated voltage not maximum voltage.

I took these paragraphs from Gecko's white papers under "power supplies". See attached. It clearly shows that a series connected motor can handle higher voltages than a parallel.

It still raises one more question though:

When calculating the rated voltage do I use the rated amperage per phase or 2/3rds the rated amperage? which would then have the maximum of 25x applied for determining the power supply voltage. Depending on the answer to this will determine if I exceed the 25x limit and if I do then I have no choice but to wire it in series.

Chris

[ger21]

Originally Posted by ChrisJ Yes. The cut sheet states that the maximum voltage is 140V. I was asking how to apply the 10x/20x rule to the stepper motor and needed a rated voltage not maximum voltage. I took these paragraphs from Gecko's white papers under "power supplies". See attached. It clearly shows that a series connected motor can handle higher voltages than a parallel. It still raises one more question though: When calculating the rated voltage do I use the rated amperage per phase or 2/3rds the rated amperage? which would then have the maximum of 25x applied for determining the power supply voltage. Depending on the answer to this will determine if I exceed the 25x limit and if I do then I have no choice but to wire it in series. Chris

Per phase.

The reason a series rated motor can handle higher voltagees is because a series wired motors rated voltage is double the parallel wired motor's.

Series vs Parallel = half the current, twice the voltage.