Greatings to all you experts!

SINAMICS V20 6SL3210-5BE31-8UV0

MOTOR 18,5W (25HP), 37,1Amp, 380V

In this aplication the motor is running at 50hz and it needs to decrease its speed to 30Hz in 1second. So if I put 1 sec in the p1121 it gives me overvoltage error but if I set it in 5sec it does decrease the speed but in 15 seconds or so.

Question is the drive re calculating the new ramp-down time according the votage is dealing with?

I was told it needs a resistor to help dump this energy exces so I looked into it but Im not sure.

If the resistor is put into place do I need to configure something else in the drive?. I couldnt see anything about it in the manual.

According the manual I need a 6SE6400-4BC12-5CA0 breaking resistor. is that right?

Cheers!

For faster ramp-down rates, the braking resistor is essential, especially if moderate ramp down rates cause overvoltage.

The way all Sinamics drives work for ramp up and ramp down time is the same (as far as I know).

It is the time in seconds from 0% to 100% speed.  100% speed is "reference speed" - something you have configured during drive commissioning.

Ramp down time is based on 100% to 0% speed.

So, if you are going from 50 to 30 Hz and want to control that rate to a specific rpm/sec or overall time, you need to know the reference speed.

Let's say reference speed is the rpm related to 120 Hz.

That means ramp down time is relative to 120 to 0 Hz - whatever that is for your motor in rpm.

Let's say your reference speed is set to 10 Hz, and the ramp down time is 5 seconds.  That means it will ramp down 10 Hz every 5 seconds. With that configuration, it would ramp down from 50 to 30 in 10 seconds.

The first thing to do is establish a good reference speed, often set to max Hz or max rpm (depending on the configuration, drive and firmware).

Let's say the 50 Hz motor can run to 120 Hz, but in your project it will never be allowed to operate above 100 Hz.  Setting the reference speed to 100 Hz makes mental math easier, but it's all the same to the drive whether it's 100.0 or 98.123.

Me, I use max rpm as the highest value I'll allow.  Then I find out the fastest it needs to run, or would be allowed to run if uncoupled from the load, and if it's lower than max rpm, use that.

Hope this helps.  It's a simple normalize / scale problem when computed in a PLC.

RDVD

Greatings to all you experts!

SINAMICS V20 6SL3210-5BE31-8UV0

MOTOR 18,5W (25HP), 37,1Amp, 380V

In this aplication the motor is running at 50hz and it needs to decrease its speed to 30Hz in 1second. So if I put 1 sec in the p1121 it gives me overvoltage error but if I set it in 5sec it does decrease the speed but in 15 seconds or so.

Question is the drive re calculating the new ramp-down time according the votage is dealing with?

I was told it needs a resistor to help dump this energy exces so I looked into it but Im not sure.

If the resistor is put into place do I need to configure something else in the drive?. I couldnt see anything about it in the manual.

According the manual I need a 6SE6400-4BC12-5CA0 breaking resistor. is that right?

Cheers!

Hello,

First off all I think read manual about braking for V20 what types are there and maybe you will get answer what braking best.

I will think what yuo need something like brake resistor because motor is huge so for him need a lot power to brake down the motor. 

If you are not sure what to do then write to this forum member Tractor he is master of inverters :)

Hi thank you for answering

Are you refering to the P2000 - Reference frequency [Hz]?

In this case the P2000 is set ti 50Hz. So if I understand you correctly since the p1121 - Ramp-down time is set to 5s it wil decrease 10hz every 1s?

Cheers!

0_Einstein

For faster ramp-down rates, the braking resistor is essential, especially if moderate ramp down rates cause overvoltage.

The way all Sinamics drives work for ramp up and ramp down time is the same (as far as I know).

It is the time in seconds from 0% to 100% speed.  100% speed is "reference speed" - something you have configured during drive commissioning.

Ramp down time is based on 100% to 0% speed.

So, if you are going from 50 to 30 Hz and want to control that rate to a specific rpm/sec or overall time, you need to know the reference speed.

Let's say reference speed is the rpm related to 120 Hz.

That means ramp down time is relative to 120 to 0 Hz - whatever that is for your motor in rpm.

Let's say your reference speed is set to 10 Hz, and the ramp down time is 5 seconds.  That means it will ramp down 10 Hz every 5 seconds. With that configuration, it would ramp down from 50 to 30 in 10 seconds.

The first thing to do is establish a good reference speed, often set to max Hz or max rpm (depending on the configuration, drive and firmware).

Let's say the 50 Hz motor can run to 120 Hz, but in your project it will never be allowed to operate above 100 Hz.  Setting the reference speed to 100 Hz makes mental math easier, but it's all the same to the drive whether it's 100.0 or 98.123.

Me, I use max rpm as the highest value I'll allow.  Then I find out the fastest it needs to run, or would be allowed to run if uncoupled from the load, and if it's lower than max rpm, use that.

Hope this helps.  It's a simple normalize / scale problem when computed in a PLC.

RDVD

Greatings to all you experts!

SINAMICS V20 6SL3210-5BE31-8UV0

MOTOR 18,5W (25HP), 37,1Amp, 380V

In this aplication the motor is running at 50hz and it needs to decrease its speed to 30Hz in 1second. So if I put 1 sec in the p1121 it gives me overvoltage error but if I set it in 5sec it does decrease the speed but in 15 seconds or so.

Question is the drive re calculating the new ramp-down time according the votage is dealing with?

I was told it needs a resistor to help dump this energy exces so I looked into it but Im not sure.

If the resistor is put into place do I need to configure something else in the drive?. I couldnt see anything about it in the manual.

According the manual I need a 6SE6400-4BC12-5CA0 breaking resistor. is that right?

Cheers!

 

Yes, P2000 (I was not sure if p2000 was the ref freq on V20, but knew it was for s120).

My understanding is the ramp down rate is from ref freq to 0 rpm in the configured time - provided the ramp down rate scaling factor is 100%.  If it is not 100%, then simply multiply the time by 1/(scaling factor).

For some of my projects, I set the ramp down rate to a very long time, like 240 sec, and adjust the ramp down rate scaling factor to affect ramp down rate via telegram.  It works very well provided extended ramp function generator has been enabled.  If the v20 provides that option, give it a try.  It is quite useful to smooth out transitions between speed setpoints, especially when the tuning is very tight.

RDVD

Hi thank you for answering

Are you refering to the P2000 - Reference frequency [Hz]?

In this case the P2000 is set ti 50Hz. So if I understand you correctly since the p1121 - Ramp-down time is set to 5s it wil decrease 10hz every 1s?

Cheers! 

I think you hit the nail on the head.

"Note: This parameter must be set to 0 (Vdc controller disabled) if a braking resistoris used."

So it seems to me that I need to commission a break resistor and set this parameter to 0 and then adjust the ramp down time accordingly to the needs of the process.

Thank you!

Cheers

Technology Team

Hello,

have a look at the V20 manual, there you can find information about Vdc_max controller (p1240), which is activated per default setting. I guess this is extending your brake ramp to keep the DC bus level in the allowed range, see chapter 5.6.2.8
https://support.industry.siemens.com/cs/ww/en/view/109780683

Information about the braking resistor are shown in chapter B.1.4.
There you can find the suitable braking resistor for your V20 and you can find information about installation and commissioning.