Baldor DC Motor info 1

Baldor spec 31-987-842
Frame 66CZ5830DD
## Describes size, mounting holes, shaft type

HP 2 (SER.F. 1.00)
## Means the motor is not expected to be overloaded much or it would be something like "SF 1.15"

Volts 28 Amps 62
## Obvious

RPM 2600 (Wound CP)
## Don't recall

(Class FX)
## The type of wire used and the temperature it can be run up to.

Cont.Duty (ENCL TENV)
## Totally Enclosed No Ventilation.
## This means there are no openings anywhere on the motor and no external fan.

Keith Cress
kcress -

The "wound CP" means that the field is compound wound. With that you will have the A1 and A2 leads which are the ends of the armature circuit, F1 and F2 which are the ends of the shunt field, and S1 and S2 which are the ends of the series field.

Looking at the motor from the shaft end, if A1, F1, and S1 are all positive, the shaft will turn in the clockwise direction. For counterclockwise direction, reverse ONLY the A1 and A2 leads so A2, F1, and S1 are all positive.

Normally, the S and A leads are wired in series to form the high current armature circuit and the F leads are powered separate from a low current field supply. It is a puzzle why the nameplate does not list the field voltage or field current.

Maybe someone else can fill in that missing detail.

If no field voltage or current is given on the nameplate of a compound motor, I would assume that the field was rated for the same voltage as the armature and the 62 amps includes the field current.
Browse the Baldor motor site. Look for the Cowern papers. An excellent collection of easy to read and understand papers on motors. I am always impressed by Mr. Cowern's ability to give accurate explanations in plain language.



Bill
--------------------
"Why not the best?"
Jimmy Carter

Hi Guys,
I opened up the wiring box, it has three wires.
Two heavy wires labeled A2 and F2, one smaller wire labeled F1. Not labeled they way I thought they might be, I suspect
F2 is A2 are internally connected.
What do you think?
Cavitate

Have you got a multimeter? Check the resistance between F1 and F2, and F1 and A2. Likely you will find a value of a few hundred ohms, but could be higher or lower.

The lower of the two readings will be from the field to the common point of the armature and other end of the field. You probably won't get a good reading through the carbon brushes for the armature resistance because the meter does not develop enough voltage, but the difference should be apparent.


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If we learn from our mistakes I'm getting a great education!

Hi Guys,
As I said previously, I have three wires out of the wiring box. Two heavy wires labeled A2 and F2, one smaller wire labeled F1. They are not labeled they way I thought they might be, I suspect F2 is A2 are internally connected.
I measured resistance between wires.
A2 to F2 = 0.5 ohms
A2 to F1 = 41.4 ohms
F1 to F2 = 40.9 ohms.

That seems to agree with my statement above "I suspect F2 and A2 are internally connected."
I also notice there are two wiring diagrams on the wiring cover plate. I have attached a picture of the cover plate.
As noted previously, I only have three wires external to the motor, so I don't know why this cover plate diagram.
Thanks, Cavitate.

Hi Guys,
I notice the motor has four sets of brushes and each set has
two brushes in parallel. The end plate has four screws and it looks like if loosened, the plate the brushes are mounted on can be rotated. I'm sure this changes some phase relationship,
can anyone give me more details.
Thanks, Cavitate

The field supply should be connected from F1-F2. The armature supply connects between A2 and F2. F2 is common to both the field circuit and armature circuit.

You basically have the circuit in the top diagram except A1 and A2 have been transposed to reverse rotation. A1 is internally connected to F2 and only one conductor is brought out. The link shown as a dotted line is an internal connection.


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If we learn from our mistakes I'm getting a great education!

Hi Guys,
Ok, So you say I have a shunt wound motor, and I'm guessing the field lead is brought out for speed control? (maybe not)
The motor is labeled 28v.
If I put 28 v on the field will it run at the stated 2600rpm?
If I reduce the voltage on the field will it run faster?
Do you think the design is a 2600rpm motor with the field in parallel with the armature and at the same voltage as the armature? ( I looked back, that is what waross said)
So, now the next phase; I want to buy a speed controller.
I'll start looking at speed controllers for shunt wound motors.
Thanks, Cavitate

Normally speed control is done using armature voltage control. It is possible to get some control using the field but usually only to run a motor above base speed. I would start with a fixed 28V on the field and vary the armature voltage. If you need more speed then you can go into the weak field area but you can't get more power out of the motor: available torque reduces as the field weakens.


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If we learn from our mistakes I'm getting a great education!

Yes ScottyUK to armature voltage control.
I'll be looking for a PWM motor speed control. I expect to connect the field to 28v and leave it.
The rest of the story;
This is an effort to get my 14 yr old interested in something other than video games. I want him to learn about building an electric go kart. No! I want him to build an electric go kart and get fooled into learning while he's building it. The 2 hp motor (got it free) is smaller than I wanted, but it will run and we can get the batteries, controller, controller drive and safety components figured out, without spending $400 to $900 for a motor. I can find lots of golf cart motors and controllers, but they max out at 36v to 48v. I'm hoping to get a 72v controller for later motor compatibility. Although if I find a golf cart controller cheap, I'll jump on!
Thanks for your help, Cavitate

Don't worry 2 electric hp will get the job done, no question.

Keith Cress
kcress -

I think I would look for a permanent magnet motor, not because they are inherently better for the application but because the field is a significant and continuous drain on the battery, regardless of the speed you're doing. If a wound field motor is what you're after then a series wound or possibly a compounded motor would be a better fit to the application. Most traction motors are series wound as their torque curve is more suited to the load.


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If we learn from our mistakes I'm getting a great education!

Hi Guys,
I tested my motor today, of course it is rotating the wrong direction.(review; Only three wires external, A2, F1 and F2) I disassembled it hoping I could find the other end of the field and reverse things. No luck, tied up and varnish, couldn't find the other end. I can mount the motor the other direction on the go kart, but it's a pain.
While I had it apart I noted the following things,
It has four coil areas.
Two coils opposite each other have thin wire, I think they are the field coils.
The other two areas look like they each have two coils in them (two different color wires) These have heavier wire. This make me think the series coil and the CPNS (or IP) coil are wound in the same slot.
These details make me think the motor is the 6 lead compound motor as shown in the bottom half of the cover plate photo I posted. Please refer to attachment.
Any additional comments or additions or corrections requested.
Thanks, Cavitate