1000HP ABB DCS800

The ABB DCS800 came out with an amazing tool added to their already popular software, DriveWindow Lite. The commissioning wizard steps the user through the paces of armature tuning, field tuning, speed feedback, speed controller and field weakening.

Field weakening, in a broad stroke, is making the DC motor go beyond its stated base speed. E.g., the DC motor has a name plate of 1,750 rpm base speed and a field of 1.5 amps. In order to go faster, the process requires 2,000 rpm. The armature voltage is already max at 1,750, so the field must be reduced (weakened) to achieve the 2,000 rpm requirement.

Parameters involved:

  • M1SpeedMin (20.01)
  • M1SpeedMax (20.02)
  • M1FldMinTrip (30.12)
  • FldCtrlMode (44.01)
  • M1NomVolt (99.02)
    1000HP ABB DCS800
  • M1BaseSpeed (99.04)
  • M1NomFldCur (99.11)

The autotuning wizard changes the following:

  • KpEMF (44.09)
  • TiEMF (44.10)
  • FldCurFlux40 (44.12)
  • FldCurFlux70 (44.13)
  • FldCurFlux90 (44.14)

What Happens

The last three are the tricky ones. The default values are better than the wizard’s calculated values. The 40, 70, and 90 work almost every time. The wizard calculates out to very low percentages. What happens is the field level and other protection faults and limits come alive beyond base speed.

The purpose of this parameter was similar to ABB’s older DC drives, like the DCS500.¬† For example, if speed “n” is selected so as to produce a motor voltage of 300 V, then 90 % will correspond to 270 V, 70% to 210 V and 40% to 120 V. The DCS400 was similar to the 800 in group four, instead of 44. So flux and field current are directly proportional. The deeper into field weakening, the less flux and current one has at a greater speed.

Opinion and Last Words

The only time that I have needed to deviate from default is with a field weakening depth of 50% or more and with high performance applications such as spindle drives, test stands and winders. Applications such as extruders and lower performance “brute force” do not. Save yourself the hassle and leave the field weakening wizard alone.