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Triac stepper motor voltage/amperage

Posted: Mon 11 Feb , 2019 19:21 pm
by Marcus
Hi all
I have an older triac which I'm upgrading.
I want to run a Centroid acorn board and a gecko g540, I also have a harmonic drive I want to run as a 4th axis from the Gecko.
The power supply I have is 48v 12.5amps, I presume this voltage will be ok but does anyone know what the amperage of the motors is. The 4th axis motor is 3amps.
A resistor is required to be inserted into the DB9 conecter on the G540, this depends on the motor amperage, Im not completely comfortable with calculating the required resistor so any advice appreciated. As you can see electrics isn't really my strong point but I'm willing to learn :D

From the Gecko manual :  

"Before beginning, be sure to have a suitable step motor, a DC power supply suitable for the motor and a current set resistor.
The motor’s rated phase current must be between 0 Amps and 3.5 Amps. Using a motor with a higher current rating will cause a
proportional loss in torque, meaning a 5A motor will get 3.5/5 (70%) of its maximum torque. The power supply voltage must be
determined by the inductance equation listed later or be between 4 times and 20 times the motor’s rated voltage. The current
set resistor may be a 1/4 Watt, 5% part. Finally have a STEP and DIRECTION pulse source available.

Connect your power supply positive to TERMINAL 11 and negative to TERMINAL 12. The power supply voltage is determined by
multiplying the square root of the motor’s inductance by 32, as in the example below for a 2mH rated motor:
32 * (√2) = 45VDC

Wire your motors to the included DB9 solder cup and secure the backshell connectors. If your motors are rated below 3.5A you
must use a current set resistor across PIN 1 and PIN 5. The resistor is calculated by taking the current in amps and multiplying
by 1000. If your motor is rated at 2.8A per phase you will have to use a 2.8K 5% 1/4W resistor. If your motor is rated at 3.5A or
above you can safely not use a current set resistor; however, your G540 will not go into current standby mode which will result
in increased motor heating. "

Thanks for any advice regarding this

Re: Triac stepper motor voltage/amperage

Posted: Tue 12 Feb , 2019 1:18 am
by moray
From my notes, the parker SD drives were set at 2A for X and Y, with Z running at 3A.

I thought I had the motor part numbers somewhere, along with the datasheets, but I can't find them. However I'm sure they were ran very conservatively. I do have my voltage calcs, which puts optimum voltage for X&Y about 57VDC, and 75VDC for the Z.
I ended up with a linear supply putting out 52VDC.

Re: Triac stepper motor voltage/amperage

Posted: Tue 12 Feb , 2019 12:31 pm
by Marcus
Thanks for the reply.
From this thread it seems the stepper amperage is 3.1 amps and 3.7 amp for the Z.
Do you think using resistors to set it at 3.1amps with the 48v power supply would be ok?

viewtopic.php?f=54&t=4248&p=16774&hilit ... ors#p16774

Re: Triac stepper motor voltage/amperage

Posted: Wed 13 Feb , 2019 22:42 pm
by Marcus
I've eventually discovered (after removing some overspray paint) the motors are placarded 3.1 amps and 3.5a amps for the Z so no resistor required for the Z as far as I can make out but 3.1k for the x and y