Over Powered stepper?

So we have a new x-axis stepper that we expected to be more powerful than the previous, but something seems off. The old X axis (and the current Y and Z axis), 425 oz in NEMA23 wired in bipolar parallel to a KL4030, at 3 amps of current. Our ways are pretty tight to eliminate play, but we've been able to move the table and head at 70ipm with 1/4 micro stepping.

The X axis motor is now driven by a 570 oz in motor. The motor is rated at 5 amp, but we've wired it in bipolar series (because the Automation Technologies website said to) so we're only giving it 2.5 amps. We're using a KL11080 driver. The x axis, no joke, now can be pushed at 375ipm! 1/4 stepping as well. It could likely go faster, but it can't get up to speed before it runs out of travel.

Normally I would be excited, except that the motor gets warm, even while idle. Not so warm as to be uncomfortable, but notably warm still. With my other motors, I never once noticed a stepper to get even slightly warm. So either

1) My new motor is getting too much of something and is on the highway to meltsville, or

2) The heat is normal and my other motors are under powered, hence less/no heat.

Can anyone shed some light on this?

The mill is an SX2.

I'm not sure what the insulation rating is on those motors, but I would not be worried if they are not uncomfortable to touch there is absolutely no issue.

Even at an idle? I can start it up, let it sit with zero movement, and in about 5 or 10 minutes it's pretty warm. Also, why would the other motors be stone cold, even after movement?

Thanks for your reply, I really appreciate the members on this forum!

There really is no "idle" on a stepper motor as soon as they are enabled the motors are powered up and holding position, so heat would be generated, but here from anaheim automations website

Stepper Motor Heating Issues
It is normal for a stepper motor to run hot (50 – 90° C). The maximum allowable temperature of the motor case should be specified by the motor manufacturer. Motor power is limited by the maximum allowable temperature of the stepper motor insulation. Class "B" Insulation stepper motors have maximum temperature ratings of 150°C. Therefore, Class "B" motors are typically rated with case temperatures of 90° -100°C after allowance for expected ambient temperatures. Higher class insulation can normally be specified to allow stepper motors to run hotter if required.

Your old steppers might have been rated at a higher voltage or because you wired them different might not have been running at their peak performance.

Awesome, thank you for the input. It seems I need to gather some more info about my steppers!

The heat is not an issue in this case. Sounds quite normal except why are the other steppers so slow? Have you ever tried to run them at 375ipm?

Can you post the stepper model numbers?

Old X axis, Y and Z: KL23H286-20-8B wired bipolar parallel to KL4030 drivers.

New X axis: KL23H2100-50-8B wired bipolar series to a KL11080 driver.

Anything faster then about 90ipm results in a loud "WEEEEEERRE" noise and no movement on the Y and Z axis. I figured it normal due to tight ways and 1/4 micro stepping.

Since your old drivers are KL-4030, you're probably using 24 or 36V, while you're probably using 115V with the new driver? If so, no wonder you have a lot higher speed and warmer motor with the new motor...

That's correct, I was using a 24v power supply. The new driver plugs into a 110 AC outlet, but does it really deliver that much to the motor? And if so, am I looking at ruining the motor?

If the motor isn't too hot to hold your hand on it for 5-10 seconds, than it's perfectly normal.

If you used the original motor with the new drive, you'd have probably gotten a 3-4x speed increase.
Those 425oz motors are about the slowest motors you can buy, and running them on 24V doesn't help at all. They really need close to 100V to get good speed from them, due to their high inductance.

The motor will be hottest when holding position. this is why some drivers have a 1/2 current idle setting. The driver drops the current down to 1/2 so that the motor doesn't get too hot. It could be that your other motor drivers have the 1/2 current feature enabled and the new one doesn't. Even so, if you can hold your hand on it you are fine. Too hot is when you can't.

Idle current reduction is a good step but for a high velocity process its easy for the eddy and hysteresis losses of the motor to exceed the copper losses, and both the motor casing and the rotor will get very, very warm.. but these are conditions not usually found in real life.

the magnets won't like anything over 80C, but neither will your fingers.

Nevermind

Nevermind, didn't notice the second page of responses mentioning the idle 1/2 current switch, apparently no way to delete a post.

Thanks for all the responses! After using it for around an hour and a half yesterday, I could still hold my hand on it for around 15 seconds before needing to stop.

But to settle my curiosity, is it safe to reduce the amperage should the motor ever start running too hot? I'm currently using the half amp switch, which helped some. Also, as an odd question, where would one attach a heat sink to these? I doubt the plastic case would be an effective location, yet that part feels the hottest.

I wouldnt worry about it. But I have seen others use fans and or heat sinks. Plastic case? Of a stepper?

"Too hot" is EXTREMELY frickin' hot! Stepper motors are generally rated for continuous operation at 85C, which is 176F - WAY too hot to touch for more than a split-second. What on earth are you worring about??

Regards,
Ray L.

I'm good at worrying :)