DC Motor rpm on nameplate

[lukin1977]

I have a question regarding a DC motor nameplate

DC Motor nameplate:
40 kW
1400/2800 rpm
V arm: 440 V
I arm: 100 A
V exc: 220 V
I exc: 2 A

I dont understand why 2 speeds? 1400/2800 rpm?
Any help?

Thanks

Lukin1977

 

[dArsonval]

The 1400 RPM rating is likely the "Base Operating Speed" of the motor when 220 Volts is applied to the motor's fields (exc),
and with 440 volts applied to the motor's armature circuit.

The 2800 RPM rating would then be the maximum recommended speed the device is designed to operate.

 

[mikekilroy]

Are you sure the 2a doesn't say like 2/1.3a? Typically they show the field weakened amp level that corresponds to the max speed (2800)....

http://www.KilroyWasHere<dot>com

 

[lukin1977]

It only says 2 A

lukin1977

 

[Compositepro]

I would guess that the motor has two field windings that can be connected in series or parallel. Parallel at 220v, 2 amp, 2800rpm and series at 440v, 2 amp, 1400 rpm. This would mean you could also use series 220v, 1 amp, 2800. There just maybe too many combinations to list them all completely, on the name plate.

 

[lukin1977]

I have checked the motor leads
Field has only two wires so there is no combinations to be made

lukin1977

 

[Compositepro]

In that case, dArsenval is likely correct except that the higher speed corresponds to the lower field voltage.

 

[mikekilroy]

This really should be easy.

As I said earlier, field does not go by voltage rating, but by current rating. Luckily tho, ohms law works so V=I*R.

So you should be able to measure the field and get R=V/I=220/2=110 ohms as verification.

Now just run the motor on the Dc field weakening control drive of your choice, up to 1400rpm with a solid 2.00amps dc on the field winding. You should then be able to measure about 440vdc on the armature, confirming nameplate data. Armature amps of course will be low since they have little to do with speed; they just make torque.

Now watching your tach (speed). since you are at armature voltage (and supply) limit, it will not change much - especially if you have properly programmed the drive for 1400rpm, 440v, 2amp field as base speed.

Start reducing the field amps from 2.00 down; this will make the speed go up. Continue reducing the field amps until you get to 2800rpm - THAT is the min field amp setting for this motor and like I said above, will probably be somewhere around 0.7amps (I thought about it some more compared to other similar size and range motors we have done in the past.) Really, this number SHOULD have been on the motor nametag as 2/.7amp.... Might you have missed it somehow? Maybe it would be good to paste up a picture of the nametag?

http://www.KilroyWasHere<dot>com

 

[djs]

More than likely the 2800 rpm is the max speed you can safely run the armature. In other words it is a speed limit, not a running speed.

 

[lukin1977]

Field Resistance: 92,7 ohm (when cold)

Attached there is picture of the nameplate

lukin1977

 

[dArsonval]

This thread continues to pique my curiosity. Thanks for posting the nameplate photo.

I believe ASEA was absorbed by ABB which is linked to Baldor now, etc... and so on.

A best answer to this question is likely going to come directly
from a manufacturers sales/engineering office.

Page 7 of this ABB pdf file URL below refers to a term called, "Speed (rpm) for alternative operation."

http://www05.abb.com/global/scot/sc...e5c1257123002ae6e1/$file/3BSM003045-1_ed3.pdf

Scrolling Baldor's website, one can find specifications for D.C. motors with 2 speed ratings here:

http://www.baldor.com/products/prod...tors&family=All+Families|vw_DCMotors&hp=50.00

In sticking with my original "guess"... a D.C. motor stamped with an additional [higher] speed
denotes the device is designed to go to that speed if called upon to do so (without flying apart).

Always enjoying this forum,

John

 

[lukin1977]

This is a compound DC motor
Leads are:
A1
A2
S1
S2
F1
F2

A1 and A2: armature
S1 and S2: series field
F1 and F2: shunt field

Could it be the 2 different speeds for: cumulative compound and differential compound?

for example:
cumulative A1-A2-S1-S2
differential A1-A2-S2-S1

lukin1977

 

[lukin1977]

for example:
F1-F2: 220 V

cumulative A1-A2-S1-S2 : 1400 rpm (440V at A1-S2)
differential A1-A2-S2-S1 : 2800 rpm (440V at A1-S1)

lukin1977

 

[mikekilroy]

no.

what is resistance of s1-s2?
while at it, list a1-a2.
you already said f1-f2=98 ohms as expected.

Your nameplate does NOT say 1400/2800rpm as your original post said; it says 1400 - 2800rpm and across from it is the 40kw rating.

I since power is constant over field weakening range, I believe this still means 2a on f1-f2, 440v on a1-a2 (or series the field comp winding like 440v to a1, a2 tied to s1, other side of 440v into s2, will give 1400rpm. Then field weaken (2a goes down) and therefore speed goes up, till max speed limit/rating of 2800rpm.

http://www.KilroyWasHere<dot>com

 

[mikekilroy]

google dc motor windings and look up that series field; I may not be remembering correctly when i say to put that winding in SERIES with the armature; it may go parallel to it - dont take my word for that as I have not messed with such a motor for 5 years. If in doubt, just ignore the S1/S2 windings - they will not be required with a DC drive anyway IIRC.

http://www.KilroyWasHere<dot>com

 

[lukin1977]

I have done some tests

resistance of series field S1S2: 0,5 ohm
as expected. series field is done with big section wire because it must carry FLA

then I connected the motor to a rectifier unit.
Vfield: 195 V was kept constant
Varm: 97 V = 336 rpm (mesured with a contact tachometer)
Varm: 121 V = 422 rpm
Varm: 147 V = 513 rpm
Varm: 180 V = 617 rpm
Varm: 196 V = 694 rpm

so at Varm 440 V the speed should be around 1500 rpm

I did the same test for cumulative and for differential conections and the result was the same

lukin1977