dc motors in paralel and one drive

Hello .

I am wondering how can i drive two dc motors with one dc drive or two dc motors in paralel and two drives in paralel at output.
Motors are 100 amps /350 v 2 pieces
drives are 210 amps /400 v 2 pieces

now one drive has one motor and drives are linked to each other in simolink and slave is following the master in torque or rpm. i am interested in putting motors in paralel .
If anybody had a project or info on that ... please .

Not a good idea. Paralleling the fields with one field supply is ok assuming they are the same voltage but doing that with the armatures will not produce good results.

Parallel armatures will not share load at all. The heavier loaded armature will draw more current forcing the lightly loaded armature to lighten up further. Speed and torque will be basically uncontrolled in either motor.

I have seen DC motors with armatures in series and that can work quite well but, from the info given, it doesn't seem that the drives have a high enough voltage rating to deal with two armatures in series.

Running one drive on one motor with a lead/follow or master/slave relationship is the right way to do this in DC.

I would not want to be party to paralleling DC motors.

paralel

A friend of mine saw a crane in Holland that has this kind of paralelling with balancing resistor on each motor . the motors are used on rotating arm of the crane .

DC motor in parallel

hi
At my plant we use 24 motor in parallel with one drive and we
use voltage control,we use motor to drive the roller table

regards

hanung

hanung // have you got any schematics / details about motor and drive?
Thanks

I have seen two motors with parallel armatures running off of one drive, but they were mechanically coupled through a transmission to a single load. And, the motors were built and balanced to the design, they weren't put together afterwards.

Other than that refer to DickDV's post above.

there are two motors coupled to a single load , the rotating arm of the crane .

Thanks

I have seen a tubing line with 2 motors on one DC drive. Each field has its own supply. The operator has the ability to fine tune the fields to make the motors some what load share. This was done by IMO some, "IDIOT" a long time ago. They were always burning motors. I installed regulated field controls and let them adjust only 1 field and it helped extend the life of the motors.

Every time I have seen more than 1 motor run in parallel on a DC drive, they have constant problems keeping the motors syncronized. That and they are constanly burning motor up.

Any money saved by using 1 drive will be spent on motors and the labor to replace them.

Do your self and your company a BIG favor and use 2 drives.

No two DC motors will ever be exactly the same. One issue is the never ending differances in communtation between the two motors. Your idea may seem to work at first, but after a while, mataining the communtators & brushes, springs, quarting etc.. will become a nightmare, especialy without leaded brushes. I would highly reccomend NOT changing your current system if it's working fine now.

Well, we have been running two motors in parallel coupled to the same load in various configurations since the early 1970's. There are a variety of ways to do it:

Shunt motors:
Monitor the armature currents independently using HED's. Set one field supply to the nameplate fixed current (about 58 amps on a GE752 traction motor). If the other motor pulls more armature current, increase its field. If it pulls less, decrease the field. If the armature currents become too diverse, call it an unbalance and alarm, then eventually shutdown.

On series motors, again independently measure the armature currents using HED's. You can only trip on a severe imbalance, as no correction is possible. Another possibility is to place an interphase reactor between the drive and the motors. Essentially, as one motor pulls more armature current, the interphase reactor decreases the impedance of the path to the other motor, causing more current to flow. Interphase reactors are typically used with parallel DC sources for AC inverters, to insure current sharing. It should work with DC motors just as well.

DC motor in Parallel

Hi
If the motor are coupled so you must use two dive so the load will be share the first drive is master and with speed control and the other with currrent control and if you want only use one drive you must use adjustable field current and load balance control

regard
hanung

I agree with this guy. If the mechanical load is common to both DC motors than each motor needs it's own drive. Otherwise, one motor will hog all the current(load), while the other regenerates back into the line(acts like a generator). They will not share load.

hanung said:

Hi
If the motor are coupled so you must use two dive so the load will be share the first drive is master and with speed control and the other with currrent control and if you want only use one drive you must use adjustable field current and load balance control

regard
hanung

Click to expand...

And bumblebees can't fly

I guess the part about us doing it day in and day out for 30 years doesn't stand for anything. We run two motors hard-coupled to a single load all the time.

There are many, many ways to do it. I gave one example for a shunt motor with independent field control. I gave another example using an interphase reactor and series motors, if you need closer balancing.

You really don't need tight balancing. Typically, when one motor starts to pull too much current, its CEMF increases (look up DC motors), causing the other motor's impedance to appear less, so it takes more current, increasing its CEMF, until they both balance, more or less. In fact, on one system (with braking) we purposely unbalance the motors to insure the lead motor (with the brake) doesn't kick in braking against the following motor. This is done with a two drive system, but we do single motor, dual drive as well. I know of several manufacturers who do similar operations with dual drive, dual motor; single drive, dual motor; and dual drive, single motor (on larger loads).

We do this all the time. We still manufacture the equipment. It is still being bought and used. I don't care if you don't agree with the principles, because we do it all the time.