pmdc motor characteristic curve?

Question

I dont understand the characteristics of a dc motor. Basically i have a rough idea of the typical dc motor specs such as no load speed, stall torque.
For the past few days,ive seen some of the manufacturer states their product in terms of nominal values.
but anyway, i want to ask about these examples :

http://www.boschmotorsandcontrols.co.uk/elektromotoren/produkt/0130063108/index.htm

http://www.boschmotorsandcontrols.co.uk/elektromotoren/produkt/0130302003/index.htm

1)Am i right to assume the nominal values as the optimum value for a dc motor?
2)How about the power source, do i need a battery capacity which is more than the nominal current,or the stall current?
3)If you look at the characteristic curve, and try to find the corresponding power/speed/torque manually and compare it with the ones that have been given on the table,its not the same.the first motor(12V):
from datasheet(nominalvalue):35W,4A,3000rpm,0.11Nm
from graph(manual method):20W,8A,4800rpm,0.11Nm

my comparison
from datasheet(nominalvalue):
35W,4A,3000rpm,0.11Nm
from graph(manual method):
20W,8A,4800rpm,0.11Nm

Answer 1

Any electric machine must have the following information on its nameplate (and therefore in a catalog cut showing the machine's performance): rated armature voltage, base speed, top speed, shaft power, current, temperature rise, and - most of the time - the insulation class of the windings.

What the data tabled below the images of the two Bosch motors indicate is the following:
MAXIMUM applied voltage is 12 volts. What this really means is that speed is proportional to applied voltage - if you use half the listed voltage, the machine will turn at half the listed speed.
MAXIMUM safe operating speed (for your process) is the listed value. You can of course operate anywhere below that value in safety by adjusting the applied voltage accordingly.
MAXIMUM value of steady state current; this corresponds to continuous (full load) torque. Exceeding this value will thermally degrade insulation and possibly other operating parameters, making your machine more likely to wear out faster.
MAXIMUM shaft power output (if you are operating as a motor, that is ... if you're operating as a generator, it's the maximum shaft INPUT power). Going above this value requires either exceeding the rated current or rated voltage (or both) - and leads to probable issues with machine performance. And of course your warranty becomes null and void ...

DC machines will continue to 'draw current' until they fail on thermal or commutation issues. There is no "stall current" condition per se (unlike an AC machine). Typically there is a commutation limit based on the machine's internal geometry - this is often set at around 150 percent of rated current for machines of this type, with some applications requiring higher capabilities. It is us to your control module to detect and correct for abnormal (i.e. high current) conditions by shutting down the system.

I'm pretty sure the curves appended are mismatched with the machines they're supposed to represent ... fairly common when setting up the website and all you have is funny graph names to work with ...

Answer 2

I had searched for DC motors previously. For your first question, yes you are right. For your second question: Battery power has nothing to do with nominal current as far as I know, so you can use any power source with a regulator which regulate the voltage to the nominal voltage of the motor. As you increase the load , the current passing through the motor will increase and at the same time the motor will start to slow down. Therefore you may burn a DC motor easily, my opnion is to use it by looking at the curves available. And at the same time consult to BOSCH abt available data.

Answer 3

Hehehe. Welcome to the 'real world' of engineering. Where no two companies present their product data in quite exactly the same way using quite exactly the same test procedures. This is why 'real' engineers always make prototypes before they release a design to production ☺

Fact is, it may be a typo on the data sheet, or someone may have put the wrong curves up on the site, or any of a dozen other things. You're best bet is to invest in a telephone call and talk to a technical representative ('tech rep') at Bosch, tell them all about your project, and ask their advice (that's what they're there for and what they get paid to do, to help customers with technical problems). They can also explain their technical data and how it should be interpreted. And most of them are good guys who are more than willing to help someone understand (and, thereby, successfully use) their products.

HTH ☺

Douog

Answer 4

the fee of the PM motor is very almost on the instant on the subject remember of the utilized voltage. (The is a small IR drop, in spite of if this is decrease than the back EMF.) to alter the fee you ought to study it to the wished velocity and alter the voltage utilized to the motor. the desirable thank you to administration the voltage is to apply a PWM technique so as that the traditional voltage is what you like. A linear voltage regulator could paintings, however the flexibility loss could be substantial.