AC Drives - AC Input current, DC Bus current

The application is using a Siemens rectifier to supply the DC busses of 42 inverters. All of the inverters are 2HP. All will be supplied through fusing directly to their DC Buss connections.

There are several considerations for sizing motors, drives, etc.. Most of these inverters are driving conveyors. Some have 2 Hp motors connected, some have 1 Hp motors connected. There are also a couple of servos, approximately 5HP each, that will be connected to the main buss.

Anyone really gotten into the trench calculations to determine the size rectifier needed to supply several drives on a common buss? I guess one particular question is...what is the formula for calculating the DC buss current load of each drive seen by the rectifier? This value is different than what would typically be drawn by the AC front end of the drive.

Which drive system are you using MasterDrive or Sinamics ?

I'm working on my first Sinamics system and the Sizer program is used to size and generate all the component parts. You will still need to decide on the utilisation though. (Can all the conveyors be running simultaneously for example)

I have not done this but, it seems to me that sizing should be done using total continuous load kw and total short-term load kw. Regardless of the type of energy, the kw has to be there in the source.

But then, as I said, I have not had to do this so someone with experience would be a better resource.

Idc=Im x 1.15
where Im = total motor HP x 1.12 ( for 460 volts motors)

Im = HP x 746 x 1/EFFm x 1/ PFm x 1/VOLTSm x 1/ (sqrt 3)

Yes. I have confirmed this with some published papers on common buss applications that are available online.

This is a Simovert 6SE unit rated at 150 HP with Control Techniques Unidrives and a couple of Control Techniques servos.

L D[AR2 said:

Which drive system are you using MasterDrive or Sinamics ?

I'm working on my first Sinamics system and the Sizer program is used to size and generate all the component parts. You will still need to decide on the utilisation though. (Can all the conveyors be running simultaneously for example)

Click to expand...

Bus sizing really is application specific. About a year ago I picked a line regenerative power supply for a 5-drive common bus application. We had 100HP of connected drive capacity supplied with a 20HP active front end. This was a center driven unwind/slitter/rewind. It was effectively a self-contained machine that swapped energy between drives. The power supply was there just to account for losses and line accel/decel.

My application is one extreme. swhite65's application sounds closer to the other (possibly). As L D[AR2,P#0.0] stated in post #2 you need to consider your utilization. If all the drives will be running simultaneously at full rated HP then you need to size for that. If only half of them will be running at any given time, size for that.

Also, assuming the drives use the standard design but without the rectifier section, with 42 drives on the bus you will have a TREMENDOUS amount of bus capacity. You should be able to stop and start several motors at a time as hard as you want without the bus voltage even flinching.

Again, it really is about utilization. Determine that before you worry about anythig else.

Keith

L D[AR2,P#0.0] are you using S7, 31xT and a CU320 or what??
I worked on a 5 axis (CU320)with 317T and a Cu310 DP recently.
I think its a great system, just wait until DCC comes out.

JRW - I'm using a 317-2DP CPU, 7 CU320's controlling 37 motor modules. This is not a motion application, just 37 independant axes controlled over Profibus.

Using servo or vector mode??
Are they DriveCliq motors??
I know you have alot of help in Manchester but let me know if I
can help. I have a few app. notes that might help.

Jay

6 vector, 31 servo, only 2 servo motors have the motor CliQ interface. Thanks for the offer of help.

Regards, Simon