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Why is the current not increasing when I apply load to the shaft of a stepper motor?

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Madbunny1

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Why current is not increasing when i applied load on the shaft of stepper motor?

Hi all,

why current is not increasing when i applied load on the shaft of stepper motor?

can anyone tell me?

thanks
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

Hi,

Do you know how a stepper motor works?
Do you know how a stepper motor is controlled?

Difficult to answer your question.
It depends whether the motor is rotating or not.
It depends on what current you are talking about.
It depends on motor driver hardware.
And it depends on whther the motor position is feedbacked or not.

In many cases a stepper is controlled in "constant current" techniqe. And the name "constant current" already says that the current doesn´t change. This is true for the winding current.
But even with constant winding current technique, switching driver and rotating motor ... the voltage across the winding changes and this makes the power supply current to increase with increasing torque.

Many different parameters will lead to different answers.

Maybe you could give more details.

Klaus
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

Hi, thank you for the reply,
I was talking about load current. Load current is not increasing even I apply the load on the shaft of the motor. If the technique is made with „constant current“. Then why am I seeing current amplification tuning option in my user interface which is provided from the program developer for the stepper motor.
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

HI,

I don´t know - I don´t have the manual by hand.
Maybe you can adjust the value of the "constant current".

Klaus
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

What do you exactly mean with "load current"? There is motor phase current and total supply current of the motor driver. The latter can be expected to slightly increase for a pwm constant current controlled stepper motor if it delivers mechanical power to the shaft.

For the "current amplification option" you'll review the controller documentation. It's no standard for stepper motor driver, the term might describe quite different control features. Too vague for a definite answer.
 

Current doesnt increase with an increase of load on the Stepper motor ?

Hi all,

I am working with a Nucleo and L6470H Eval board to control a stepper motor. Using the SPIN evaluation software I gave the values for Holding current, Target current etc. But when I run the motor, the motor is drawing the current (0.6 A) without any load, and the current is not increasing when I tried to increase the load on motor.
 
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why current drawn by stepper motor doesnt increase when load is applied on motor?

Hi all,

I am working with a ST-Nucleo board and L6470H Eval board to control a stepper motor(QSH4218-51-10-049). Using the SPIN evaluation software I gave the values for Holding current, Target current etc. But when I run the motor, the motor is drawing the current (0.6 A) without any load, and the current is not increasing when I tried to increase the load on motor, but the motor started missing the steps. Is this common with stepper motor?

Can anyone suggest me a solution.
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

A stepper motor works quite differently than an AC or DC motor. Generally (forgot about microstepping for now) you apply a constant-current to the windings. The speed of the motor is NOT proportional to voltage or current, as it is with other motors; it's proportional to how fast the windings are switched.
 

Re: why current is not increasing when i applied load on the shaft of stepper motor?

Do you know what the actual load torque and inertia is? Did you check the operation parameters against motor specifications?
 

Re: Why current is not increasing when i applied load on the shaft of stepper motor?

Hi all,

why current is not increasing when i applied load on the shaft of stepper motor?

can anyone tell me?

thanks

It depends on load which you applied and many conditions as well. Please post the conditions and type of load. A current vs RPM helps understand the behaviour of current vs rmp for different loads, you see current has no impact for a blue load (1e6), image below from **broken link removed**:

Current-vs-RPM.jpg
 
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Re: Why current is not increasing when i applied load on the shaft of stepper motor?

Rload? What does a resistor have to do with this?
 

Re: Why current is not increasing when i applied load on the shaft of stepper motor?

The diagram describes the characteristic of a stepper motor operated as generator and hasn't much to do with the original question.
 

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