Sir,
I have a stepper motor with following ratings:
Rated voltage: 3.71 volts Phase current:3.50 amps Phase resistance: 1.06 ohms Phase inductance: 4.35 mH Holding Torque: 4.50N

can you please tell me how to decide the ratings of the power supply to be used for this stepper motor? Thank you in advance.

 

The label says the maximum current is 3.5 amps and the maximum voltage is 3.71.
If you use mosfets to drive the windings, you won't need more than a few tenths of additional voltage.
So, make a supply with the ability to supply 3.5 amps and a voltage of about 4 volts.
Unless someone that knows more than I steps up to this question.

 

Sir,
Thanks for such a quick reply. I tried to rotate the motor using 24 volt 2 amp power supply, but did not rotate. I tried to rotate the shaft with bare hands but became too tight to rotate. Without the power supply, I was able to rotate the shaft with hands. I fear the motor is working or not. Another question is , Can I use a power supply of 24 volts and 4 amp power supply?

 

Please using the normal fonts unless you have something to emphasize.

 

Control of Stepping Motors
A Tutorial
http://homepage.cs.uiowa.edu/~jones/step/index.html

 

Do not connect any voltage higher than the motor rating or you will overload the windings and they will burn out. Stepper motors do not rotate unless they are controlled by switching the windings on and off in the proper sequence. You will need to build or buy a controller circuit for the motor. Read the link above.

 

Stepper motors do not rotate when voltage is applied, they step (sometimes they are very small steps).
You need a stepper driver like an L379 chip and a source of pulses to initiate each step (the driver will take care of which coil on the motor to energize and make steps in sequence to make the motor turn).

In easy terms, you will need some electronics to go with a stepper.

Quick-start guide
http://www.freescale.com/files/microcontrollers/doc/app_note/AN2974.pdf

 

A stepping motor of this type operated at it's nameplate voltage and current will not perform very well, the torque will fall off very quickly with speed. Typically you would use a current regulating 'chopper' drive (PWM) that runs from a much higher voltage.
The rated current should not be exceeded, but higher voltages allow quicker current build up, hence more torque at high step rates.

The nameplate ratings just tell you about the DC characteristics of the coils for the most part, and the max power dissipation.

 

As stated the name plate current should not be exceeded, when using a PWM controller and a DC supply significantly higher than the name plate voltage, the subsequent Mean current can be kept constant at the plate rated value by varying the PWM pulse width.
The maximum torque is when the motor is stationary with the motor rated voltage and subsequent current applied.
A higher DC voltage and PWM are the means of maintaining this as the inductive reactance increases with rpm.
Max.

 

Do not connect any voltage higher than the motor rating or you will overload the windings and they will burn out. Stepper motors do not rotate unless they are controlled by switching the windings on and off in the proper sequence. You will need to build or buy a controller circuit for the motor. Read the link above.

Thank you sir for your patient reply. Now I am beginning to sense with what I am dealing with and how serious the stuff is. Now that the crime is already committed, how do I check if my motor is working or not?

 

thank you all the members who had patiently replied to my queries. I indeed look forward to you to deplete my ignorance and prevent myself from committing some stupid mistakes as the one I had mentioned above. thanks to all once again.

 

Do not connect any voltage higher than the motor rating or you will overload the windings and they will burn out. ...

I take issue with the part about voltage. You can put any voltage you want across the windings as long as you limit the current. It is not uncommon to drive stepper motors with a bi-level power supply. One power supply for switching current in and out and the other for holding.

 

I take issue with the part about voltage. You can put any voltage you want across the windings as long as you limit the current. It is not uncommon to drive stepper motors with a bi-level power supply. One power supply for switching current in and out and the other for holding.

My warning was to the OP, who had apparently connected a 24V, 2A power supply to his stepper motor that was rated 3.71V with no mention of current limiting. His next step was to use a 24V, 4A supply. It didn't seem like a good idea to me.

 

My warning was to the OP, who had apparently connected a 24V, 2A power supply to his stepper motor that was rated 3.71V with no mention of current limiting. His next step was to use a 24V, 4A supply. It didn't seem like a good idea to me.

In light of the fact that he had no concept of stepping the phases I agree. My point was simply that if you know what you are doing there is no reason to construct a supply that is equal to the voltage on the nameplate because the simple but wasteful solution is to use big fat power resistors to take up the slack.

 

The restive method was previously used prior to the more popular PWM version.
Max.