First test risks?

I want to test one servo motor and amplifier before I do all 3 axis.
Using a mesa 5i25, 7i77, AMC servo amp, and Dc servo motor, and fully configured emc2 for 4 axis.
My problem is not knowing what I don't know. Meaning how can I mess this up?

What I know:
Disconnect belts on milling machine for all axis.
Run Test mode on AMC amp per their manual.
Don't get shocked on condensers (140vdc) Still need a resistor to drain at shut off but not sure what size?
Set up Mesa boards with 5v and 24v Field Power. I made a power supply from 12v transformer, two h-bridges, and condencers to get 20vdc. Seems good but what do I know?

The above is all good to go however I have found out the hard way all this stuff can get destroyed with one push of a button. Don't ask.
Any issues to look out for before I hold my breath and proceed?

A couple of random notes:

Double check power supply connections

Beware of simple transformer/rectifier supplies because
they can output huge currents if shorted, so alway fuse!

I would get limit switches and drive enables working first, then
get the encoders working and scaled properly, and only then
enable the drives and get the feedback direction set.

Disconnecting motors from linear motion components is good as you are
likely to have runaways, but once running with feedback control you must
re-assemble to tune the PID

PCW wrote:

Double check power supply connections

Beware of simple transformer/rectifier supplies because
they can output huge currents if shorted, so alway fuse!

Having had a few customers reverse the power on my servo amps, the fuses don't react quickly
enough to save the semiconductors. it makes quite a mess! So, best to TRIPLE
check the connections!

Peter's other suggestions are all very good, too.

Jon

What about damage from mismatched amplifiers and motors? Buying the older components you can't always be 100% sure of the specs. Can you burn amplifiers out by going too big or small on amp rating for your motor? How about mismatched voltage rating? You find the 100vdc servo amps and the 140vdc however motor specs are not always clear. I'm concerned about damage more than if they work good or not.

You absolutely need to make sure that you do not apply a higher DC voltage than the drive is rated for.

You should make sure the the drive current limit is close to the motors peak current rating
This is often about 3 to 5 times the continuous (stall) current rating of the motor.

If the peak current rating of the drive exceeds the motors peak current capability,
you risk overheating or even demagnetizing the motor (especially true of older non-rare earth magnet motors)

If the drives peak current is much less than the motor ratings, you will not get good performance
(low torque)

I would not worry about motor voltage ratings too much as long as they are within 30% or so
(adjust your DC motor power to match as long as you do not exceed your servo drive specs)

I went out to check my best commercially made cnc milling machine to compare the motors to the amp. specs.
Noticed they only matched the continuous stall current and ignored the motors max. current.
Continuous motor current = 12A
Max motor current = 65A

Amplifier Continuous current = 15A
Amplifier Maximum current = 25A

The manual says the amplifier (Servo Dynamics) has a built in RMS Protected Circuit that kicks off if the current is too high for extended period of time.
My question is can I do the same with a fuse? Assuming I happen to use a amplifier without the built in circuit.
The above mentioned machine has a 10 amp fuse on the power supply.

greeder88 wrote:

I went out to check my best commercially made cnc milling machine to compare the motors to the amp. specs.
Noticed they only matched the continuous stall current and ignored the motors max. current.
Continuous motor current = 12A
Max motor current = 65A

Amplifier Continuous current = 15A
Amplifier Maximum current = 25A

Yes, putting 65 A into the motors could easily break things. belts for sure, possibly even couplings
if the motor is set up for direct drive. You can figure out the mechanical advantage of the
leadscrew and multiply by motor torque, and may get a really frightening number in
pounds of linear push to the table.

The manual says the amplifier (Servo Dynamics) has a built in RMS Protected Circuit that kicks off if the current is too high for extended period of time.
My question is can I do the same with a fuse? Assuming I happen to use a amplifier without the built in circuit.
The above mentioned machine has a 10 amp fuse on the power supply.

Probably not. The problem with switching supplies is they are POWER in = power out minus
losses. So, if the amp delivers the current limit setting to a stalled motor, there will
be very little power from the main DC supply. P= i squared * R, so 20 Amps squared * 1 Ohm
is 400 W. With a 100 V power supply, that would only be 4 Amps input. What you can
do is put a very low Ohm resistor in series with one of the motor leads and strap
a PTC thermistor to the resistor. Something like .1 Ohm or maybe even less. This
will have a thermal time constant of probably tens of seconds (depends on the
size of the resistor). The PTC thermistors can then be wired in series with the
E-stop switches. You may actually need some kind of simple sensor amp
to detect when one of the thermistors goes to high resistance. These PTC
thermistors can be had where they have a sharp transition to high resistance
at various temperatures.

Jon

I tried to look into that circuit and like they say in the military "Way over my pay grade". I'll have to make sure I use amps that have the RMS protection circuit.

I'm finally all configured and hooked up and ready for servo drive power to the motors.
However this is where I was when I destroyed a bunch of drives the first go around.
That was with a totally different system and it was the e-stop circuit that caused the drives to short. ...who would suspect that.
Anyway I want to get a single motor turning with the battery to the drive control idea.
I did some searches and found people suggesting a 9v or 1.5v battery.
Can I get a little more detail on using a battery for the 10v +,- control signal to the amplifiers?
Can 1.5v ruin a amplifier hooked up to the wrong pin?

Thanks

A 1.5V battery has pretty high short circuit current so could damage a forward biased diode for example.

If you want to be safest, use a 1.5V battery with 1K to 10K series resistor.

Also be VERY careful to keep away from power connections