DC Braking With MM440 Frequency Regulator

Hi,

The first motor of a productionline has to stop real fast. Ow, btw, it's a carpet factory.

The Drive is controlled on profibus.

I see that Parameter P1230, 1232 1233 and 1234 are inportant.

What's the best method to stop real fast with DC braking.

Using an OFF1 and DC brake 1 second for example ? The start frequence, what should that be, it must brake always, at any speed.


Great thanks

bye

Combo said:

Hi,

The first motor of a productionline has to stop real fast. Ow, btw, it's a carpet factory.

The Drive is controlled on profibus.

I see that Parameter P1230, 1232 1233 and 1234 are inportant.

What's the best method to stop real fast with DC braking.

Using an OFF1 and DC brake 1 second for example ? The start frequence, what should that be, it must brake always, at any speed.


Great thanks

bye

Click to expand...

hi combo, I don't think you can stop a motor without deceleration first, because you mentioned "at any speed"... therefore you need to check what is the max speed the machine might reach, and set the brake to handle that particular speed, if you do brake the motor on the max speed, then you can stop it at the low speeds for sure.

I know this is not great help...just a thought.

ps: read the data CD supplied with the drive... P0701 => P0704 parameters are for the control of digital inputs, you can triger DC injection brake via digital inputs(or via profibus).


best regards.khalil

You may want to check and see if the motor can handle that type of breaking method. (Dc Injection) As well as, can the shaft handle that much torque with out twisting off. You may want to reduce the speed of the motor before trying to use DC injection by another breaking method. It's just a thought.

I think DC braking is the best way to bring a motor to a (uncontrolled) stand-still in the shortest time. Any motor will accept that as long as u dont do it to often because the motor will really heat up.
If the vfd does not go into "overvoltage" or "overcurrent" there is no problem.
If it does, adding a breaking resistor will solve this problem.

Pego said:

Any motor will accept that as long as u dont do it to often because the motor will really heat up.

Click to expand...

If you are worried about motor overheating then have a rewind firm tape thermistors into the motors phase windings, put a thermistor control module in the panel to stop the motor starting again if its too hot

I would stay completely away from injection braking. Really, you can stop a motor much faster by letting the drive control the rotating field to bring it down to zero speed at full torque limit. You will need to install, at the very least, an external braking resistor, and depending on the cycle-times, possibly even an external chopper assembly.

DC Injection braking is useful for bringing a passivly rotated load (say, and HVAC return fan) to rest prior to starting it, or as an extra safety brake (but honestly, if you need a safety brake, you need a mechanical one).

Set the drive's decel time to the time you need. If it trips on overvoltage, you need an external resistor. If it still trips, you may need to spec in a different braking unit. The master-drives choppers can work just fine with a 440. If you absolutely require ultra-fast stops, consider a mechanical brake.

rdrast said:

DC Injection braking is useful for bringing a passivly rotated load (say, and HVAC return fan) to rest prior to starting it, or as an extra safety brake (but honestly, if you need a safety brake, you need a mechanical one).

Click to expand...

I do not agree with that, if u need a holding brake, use one, if you dont..DC breaking wil do fine,

Well, if you want to bring an induction motor, controlled by a VFD, to a stop, in the shortest time, then injection braking isn't it.

Regenerating or Dissapating the excess bus voltage by having the drive produce 100% (or 150%) negative torque, from operating speed to zero OR by killing the drive and clamping a mechanical brake will both bring a motor to zero speed faster, and generally in a more controllable fashion.

As you can see, braking on an inverter is not necessarily a simple matter.

In an attempt to clear things up a bit, there are several independent issues.

First, do you need a controlled, predictable stop ramp? If yes, your only choice is setting the drive to ramp to stop and adding however much snubber brake capacity is necessary (brake chopper module and resistor). You cannot stop with more braking horsepower than the drive current limit capacity permits. If your answer is no, then you can accept a short stop with light loading and a longer stop with heavy loading. In that case, DC injection is an option but will not develop the braking torque of other methods. If the stop isn't fast enough, then a mechanical brake must be added. The drive must be programmed to coast to stop for either DC injection or mechanical brake. Also, expect to replace the friction elements in that mechanical brake occasionally.

Second, the motor concerns mentioned in above posts are largely not really concerns. The only motor damage potential exists if the DC injection current doesn't turn off when the motor stops turning.

Third, if stopping fast is your only concern, then you have the above choices. If, however, you must deal with rapid speed reductions without stopping, then the ramp stop with snubber braking is your only choice. Neither DC injection or mechanical brakes can be used to slow down without stopping.

Finally, it is possible to have a situation where braking horsepower is larger than the motoring horsepower. In those cases, you must size the motor, drive, and braking package to the larger braking horsepower.

Hope this helps.

Hi

It is not a safety brake; it must be a fast brake (but not that fast); 1 second is good.

I set Parameter P1230 with an ON/OFF1 bit

and a duration of 1 Second,

and it works, can someone explain me P1230, I don't really understand why it works with the bit ON/OFF1; P1230 is an Enable DC Braking parameter; it must be on while braking ?? But when I aplly an OFF1, then it works also ??


BTW: I know that a resistor or a mecanical brake is better; but my boss didn't buy these things and asked me to use DC braking.


regards