We Have Two DC Motors of 1550kw Having Different GD2

Are the motors same, except for GD2?

It is not likely, field time constants [ or Field current vs speed] may have greater difference than inertia.

What are the GD2 values?

I am sure master-slave is possible, but what is slave & what parameters? It would seem best for low GD2 (faster response?) to be slave.

Slave gets same speed target value from master?

Slave gets measured torque value from master & tracks it?

Slave tracks actual speed of master??

??

Motors are same but two different manufactures.

Field currents are same connected in series with one drive.

during trial new motor responce time geting sluguish tuning done at max level,

current hunting form positive and negative quadrant (+20%,-14%)

Find below graph.

We have interchanged master and slave motor but same problem.

How to improve responce time and what are reasons of current hunting.

May be problem in design of motor.

The problem as I see it is that the motors will draw different current at full load, so the drive will be oscillating between the two....you need to balance the load electrically, possibly by altering the voltage to the second motor....I would lower the voltage to the lessor motor....this should balance the amp load...

Are you running both motors as speed regulators, or one speed and 2nd as torque follower? Usually current excursions you show are due to load and/ or driven equipment, especially backlash in gears, if regulator is tuned too hot. Gear lash usually determines the ultimate response possible. It would be unusual for the motor rotor Wk2 or GD2 to be a significant portion of the total, even reflected back through the gearbox, so you may be attempting to compensate for an insignificant variable in the drive motor.

Also, dc motors fed from a common field supply are usually fitted with trim resistors to force the match of the torque gain for each field winding. I assume this is done at steady state, adjusted so the armature currents are equal, but I’ve never done this, always used separate field supplies.

That's the topic of a discussion with the manufacturer of the <...DC drives...>, which might be best addressed by telephone, perhaps?

You don't say what type of DC motor they are, series, shunt or compound, please provide more information.

DC shunt motors.

Field winding connected in series.

Both motors drive one gear box in same direction.

Used for reversible bloom rolling mill.

May be my North American background - "GD2" I don't recognize.

Are they on one drive or a drive each?

..."G is mass of motor rotor, D is the average (or effective) Diameter of the mass. Larger GD2 means more difficult to start up the motor. Smaller GD2 means easier to the start up. Each motor has different rotor GD2. ask motor vendor for a data-sheet."...Apr 4, 2009

http://search-ext.abb.com/library/Download.aspx?DocumentID=9AKK107045A5113&LanguageCode=en&DocumentPartId=&Action=Launch

OK, equivalent to WK2.

In my experience the motor electrical characteristics are more significant than the inertia. Different manufacturers have differing windings and even tho they may be straight shunt they may still have interpoles and some stabilizing windings. The droop characteristics and armature resistance may be (probably) different.

Depending on the gearbox, the motors may have different rotations and the A1 A2 S1 S2 F1 and F2 windings all have to be correctly connected or you may find one machine deferentially compounded - and that leads to chaos.

When we were forced to have two motors on a common armature supply we often added resistance to one or both armature circuits to balance the per-normal IR drops of the motors so they would draw their current share.

My preference was always one DC drive per motor - motor protection and load share becomes trivial.