Electrical Questions

[Mosey]

Don,
The motor is a Bodine 115 v Direct Current speed control motor NSH 500, which I am connecting to a new KB KBMD-240D DC motor speed control. The controller has an armature fuse and a power resister both sized for the 1/8 hp motor, and the controller is set for 115v.
Do you mean that I should disconnect the motor from the controller while I test the current on the 2 Armature lugs with a (30 watt) light bulb to see if the speed dial will control the lamps brightness?
I have adjusted the min speed trimpot so that at zero on the speed dial the motor stops, and with the max trimpot all the way to it's max, the motor speed is not going nearly high enough.
Mosey

[stevehuckss396]

One thing that might be preventing you from getting max speed is you have a 115 volt motor and the controller only puts out 90 volt.

[Mosey]

Don,
I noticed that they say that maximum speed trimpot range is 50-110% of full speed for SCR rated PM  motors. I don't know what that implies.
I will call them tomorrow to see what they say.
I think max speed is about 750 rpm.
Mosey

[Don1966]

Mosey the drive you have is a dual voltage drive. It can be connected to a 120VAC or 220VAC source. You must make sure it is setup for 120vac. The unit is also scaleable for different HP motors, you have to select the proper resistor for your motor. This resistor is a current limiting resistor and is scaled to your motor HP like I said. If the wrong resistor is inserted it can limit the speed of the drive by limiting the current it pulls. Check the specs sheet that came with the drive for the proper resistor, again this is a plug in resistor Usually about 1/2" X 1"".

And yes you have to disconnect the motor to do the bulb test. Also put you meter on it to see if you get 90Volts DC like Steve said.
Also the max speed trim is right and all this does is reduce or increase the voltage the speed adjust sends to the drive, usually 5 to 10 volts DC on the center wiper of the speed pot. Min speed trim elevates the voltage reference from zero reference to about 1VDC and you will notice the drive start to turn.
Ok check your specs. and PM motor are permanent magnetic motors, no fields.

Don

[Mosey]

Don,
See my post below for the answers to your post.
It is set for 115 volts, not 240.
The resistor and the armature fuse are sized for this motor and are in place.
This is a shunt motor, as shown on the plate under type NSH, which I believe means that. KB specked the controller based on the motor type NSH as being a shunt motor and picked this controller for it.
I'll check the voltage tomorrow when I get in.
Mosey

[Don1966]

Oh yea, sorry I must of missed that post. But do check to see what voltage is coming out of the controller.

Don

[Mosey]

OK, cool, I will check the voltage.
If the max voltage were 90 instead if 115, I would expect the motor to run at 75% or more of it's rated 1725 rpm, or about 1350 rpm. I can't measure rpm, but I guess it reaches 500 to 750 max. Not good enough for sure.
I'll let you know what I find.
Mosey

I can't check until later, but noticed that the manual says that at 120 vac line voltage, the motor voltage is 90-130 vdc. So, if it isn't putting out enough voltage, then it is wired incorrectly or faulty. I'm voting for wired incorrectly. We'll see.

[Mosey]

I spoke to Bodine today and obtained the correct wiring diagram, verified that I was wired correctly. They are super  helpful, researching the schematic from archives and helping me understand the correct setup. Checked voltages and they are right also, with 0 to 120 volts on the motor when turning speed control. They think there may be faulty armature segments, buildup of carbon on the mica, and suggested I pull it open to check for shorts.
So, I either rebuild motor or get a new one.
At least I know that controller is wired right and working.
I learned a lot about motors and controls in the process.
Mosey

[Don1966]

Mosey do you see any signs of arcing on the commutator. If you had a short in the armature it would spark excessively. This would show up on the bars, but not the one that's shorted. It would generate heat in the motor and also draw more current. One thing you can do is clean between the commutator slots. The gap in between the bars should be below the metal. If not take a hacksaw blade and thin it on the bench grinder to fit the slot and clean between the bars to below the copper. This is mica in between these bars and is harder then copper so get it below the copper.

Now I tend to agree with Dave that the field resistance seems a bit high. Make sure when you take the reading again that you don't touch the meter leads. This reading could be your body resistance.
If the readings is the same, try to find the cross over jumpers between the windings. Clean the wire and measure one coil resistance at a time. They should all be the same.
This should give you something to try and let us know what you have.
I am glad your controller is OK. are the voltage readings with the motor connected? If not take it again.

Don

[Mosey]

Don,

Solution of this motor problem will have to take a back seat to finishing my engine for a while, as I promised not to let other things shut me down.
I will tear into the motor when I can, as it is an area in which I am lacking in experience and am anxious about..
Thanks, I'll be back.
Mosey