In Order to Understand Bldc Motors and Their Working Principle, I Read a Lot on the Web, and I See T
Steppers are intended to work in a open loop without feedback. The current trough windings is preset to a constant value at the driver (chopper) and the rotor is hold at certain position...all the theory you have already seen on the web. If we closer look at the holding position of stepper motor, we can notice that torque is zero, because the rotor field and stator field are alligned. A max torque is produced when you want to move the rotor from its holding position, looking electricaly this is 90 degress difference between rotor field and startor field - you can use two magnets to proove that, the force is maximal when magnets are placed 90 degress from each to other. With BLDC and PMSM you have a feedback, as you depicted a hall sensor for proper commutation. If you look carefuly the stator is always commutated in such way that stator field is 90 deg with respect to the rotor field. In this case the rotor would give max torque always, therefore you also need a current regulator.In few words: The current trough BLDC is always proportional to the output torque of the motor, at standstill with no static load, the current is zero. The stator field in the BLDC is always oriented to be 90 deg shifted with respect to rotor filed.
1. What is PBH?
Please specify your term as I Google this and found many aspects related to various fields. So I just only say that this term may be related to:PBH = Pratapgarh ( A district of Uttar Pradesh)PBH (Precision Bearing House) is one of the leading Industrial Automation Suppliers & Manufacturers in India with products supply such as Maxima Aluminium Profile, Stepper Motor, Stepper Drive, Actuators, Linear Guide, Ball Screw, Hardened Shaft, Cable Drag Chain.PBH is also a test in Mathematics.So you have to mention with which field your term is related. What is PBH?.
2. Choosing Stepper Motor - Driver Combination
Sparkfun.com has some good tutorials on PCB design with eagle which is free. (with some restrictions). Upverter.com is also a good place to cut your teeth on, the learning curve will be slightly higher but less part creation which will save you time. As far as PCB design goes, make sure you have adequate power caps next to power hungry IC's. Find a PCB trace width table on the internet and make sure your traces can handle the current going through them. Typically you make big powerground planes because it lowers the inductance and resistance of the copper on the board. You can think of each trace as a tiny resistor and inductor, you can actually calculate the values of each trace/plane. A big ground plane also gives a place for RF from processors or PWM to go to and makes traces less of an antenna. If your doing a two layer design it makes fitting the power planes into the PCB more complicated because you it forces you to run traces through your ground plane. This is where PCB design turns into more of an art, you are trying to balance multiple requirements. The picture here kind of illustrates this. make sure your schematic is sound, check all inputsoutputs and vcc and ground. Do they make sense? did you reverse anything? Did you get all the pins right and correct to the datasheets? Then check the PCB. Are the pads the correct sizes on the parts? Do you need mounting holes? Do you want test points to make it easier to troubleshoot? (Oh and vias carry current, did you size those right as well?)Then send it off, if it works 100% after you stuff it you will be my hero.
3. Why is it better to ramp a stepper motor than not?
The moment of inertia for the driven system may be significant, and the motor cannot accelerate to final angular velocity without putting very high torque on the shaft. You want to limit that torque, so the motor does not stall (miss a step), or overstress (twist) a shaft, or a cause a coupling to slip. Ramping the angular velocity up (and down) does this.If there is 'stiction' in the moving system (as, when a lubricating film must be reestablished by rotation), slow initial steps can help (but ramping down does not ) .Steppers move in a jerky fashion, there is significant acceleration on each step, so it is common to use a compliant motor coupling (with some springiness) in order to smooth the rotation of the driven system. In a system WITHOUT a compliant coupling, ramping might not be as effective.
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