How to generate constant torque 1

[sydro]

I have an asynchronous machine.
I want to use it as a brake, it means it has to set a constant torque.
How can i do this?
I have to modulate a load resistance or capacitor? How?

 

[7anoter4]

There are a few way to brake an induction motor. If you don't intend to use DC or VFD then the counter-current operation induces pronounced braking reaction. The current impulse on switching over is considerable greater than starting through direct connection. The motor is generally braked in star connection in order to avoid too great a current.
The motor must be disconnected in good time from the mains so that it does not again accelerate in the new rotational field direction. This is mainly made automatically.
However, in order to reduce the current, suitable resistance has to be inserted in series with the supply.
See [for instance:]

http://kmc.co.rs/sites/default/files/2112f-Brake Motors PATAY_3463c_en.pdf

 

[sydro]

Thank you for your answer 7anoter4!

What about if I want to use Active brake?
I mean, if I want to brake setting the motor at a lower (or at worst case, reverse) speed than the other motor.
In this case, how can I control the constant torque?

How can I manage the frequency (or voltage) of the motor to control the torque?

 

[sydro]

Ps. I can have this information:

The rotor speed (I have an encoder)
The output voltage and current

I don't have the angle or the cosphi

 

[7anoter4]

I think the GE Brake Resistor Design Guide could be useful for VFD braking resistance calculation. See:

http://www.geindustrial.com/publibr...=Installation and Instruction|DET-700|generic

 

[jraef]

Anything related to using an altered frequency to achieve braking involves having a Variable Frequency Drive on the motor. Once you have that, then Dynamic Braking becomes simple. All VFDs are capable of Dynamic Braking, but some need an external module added that provides the DC Bus sensors and DC chopper transistor to fire off excess load energy into braking resistors. To properly apply it, you must also get a sense of how long you will need to brake or how fast you need to stop the motor, and how often you need to do it.

If your plan is to brake continuously, as in speed control on a down hill conveyor or something, then Dynamic Braking may not be the best choice, in that case, I would look into using a more expensive vFD that is capable of Line Regenerative Braking. Line Regen Braking puts the energy from the moving load back onto the line source (energy recovery), which can be done continuously without regard to duty cycle as long as you don't exceed the current rating of the motor.

"Will work for (the memory of) salami"

 

[DHambley]

Is your motor driven from your own drive? This drive should be able to operate bi-directionally. Generator mode runs similar to a PFC control on an AC/DC supply. If you have a high-energy storing source like a battery, the braking energy gets stored onto the battery. If your power source is the grid, your system would also need a bi-directional 60Hz supply.

 

[milmat1]

The answers above sound spot on to me. I often ask questions concerning safety equipment and devices myself. And I usually get the same answer, "Doing a risk assessment first will tell you more about what needs to be done"

Your the person they elected to do this project so they need to listen to your judgment here. Because all the discussion in the world will matter very little to the person who falls in there...

Regards,
Matt