Hi there!
I have a trouble with the determination of the effiency of my stepper drive. It does not produce enought torque and now i do not know that the problem is in a mechanical design or it is an electrical drive fault. The drive was design with preliminary measurements of the neccessary torque then it was multiplied with a 1.35 factor and then i got the maximum torque what is needed. 18-19 Nm was measured so the drive was sized to 25 Nm. I choose a relativly big stepper (MS 600 HT-2 which has 6.8 Nm holding torque and from the torque curve of the stepper it has ~5 Nm pull in torque www.isel.com/.../ms_300ht2_ms_600ht2_ms900ht2.pdf ) and I used ribbed belt in the transmission. I use the drive in slow speed (30-60 RPM) with full step so i can presuppose that it has ~5Nm torque during each step (from datasheet torque curve). The ratio of the drive is 5.13 therefore the drive can produce 5.13 * 5 = 26.5 Nm torque. I cannot measure the output torque of the drive because i can measure only static torque due to the available measurement method (dynamometer). So in theory the drive should has enought reserve torque to do his job, but in reality it does not.
DRV8711 booster pack was used to drive the stepper motor with 12V supply voltage. The motor needs 3.5A/phase current in series connection which can supplied from the booster pack (it has 4.5A/phase max current). My question is starting here which factors are take apart in the determanition of the max torque? If i measure 3.5A with a multimeter during stepping does the motor have max torque?
In the constant current drive how does the motor torque depend from the PWM frequency, Ton, Toff, decay modes, the chopping VM voltage, stepping operation ... etc?
So to assume my need i want to use my drive with maximum output torque in slow speed and how should i parameterise the DRV to get that.
Rob
