Hello

We have a stepping motor on turbine governor to increase or decrease speed. There is no diagram or name plate. The motor have 4 leads where 2 are joint together seems to be common say black and other two are separately coming out say red and yellow. we connected 220VAC neutral to common black and line to one by one red and yellow for forward and reverse direction movement. The problem is if neutral is with common black once line connect to red wire, motor move forward. but if switch off and again ON with same connection, the motor move in reverse direction sometime, with same connection move forward and some time reverse. Kindly advice if somebody have experience.

Regards
Shaheed ul islam
DI Khan
Pakistan

 

It's behaving as a synchronous motor and will start up in a direction depending on the physical location of the rotor and the line polarity at the instant of connection. This would be expected with a stepping motor driven improperly. Proper drive produces a sequence ensuring direction.

Regards
cww

 

Shaheed:

1) Do you have some idea of the torque (kg(f)-mt) required by the shaft the "stepper" motor is connected to?

2)Why did you assume the motor is 220V, AC?

3) Can you provide the resistance value between the 3-leads?

Regards, Phil Corso

 

> It's behaving as a synchronous motor and will start up in a direction
---- snip ---

Thank you, You mean the stepping motor is out of order and we have to replace it, Am I right?

Regards
Shaheed

 

No, the motor may be fine. If it is a stepper motor you don't simply hook it up to the line. You use a stepper motor drive. I'm actually quite surprised it survived, which may mean that it's not a stepper but some other type of motor. You should wear a face shield when hooking miscellaneous items to house power. Steppers are typically driven with switched DC of lower voltage. I would do a little more research on whatever part of the assembly is identified to see if you can get a clue to the proper driver.

Regards
cww

 

Hi Curt Wuollet,

The rotor of this motor is in two parts consisting some type of teeth, permanent magnet and satator small sets of coils so its construction seems to be a stepper motor. I hooked it up to 220VAC in the series of a 100W lamp but also checked directly. it moves some time forward some time rev as you told according to the rotor placement. I have also hooked it 24VDC, to 220VDC but applying DC motor does not move. I think you are right some kind of drive circuit would be required that is not clear to me. Your help shall be appreciated for more information.

Regards
Shaheed

 

Hi, Phil Corso:

1: We don't have any data but it is driving small shaft of turbine governor like serve motor of UG-8 woodward.

2: I applied 12VDC to 220VDC first in series of a 100W lamp and then direct but the motor did not move. Again I applied 220VAC in series of 100W lamp the motor rotated, applied direct 220VAC the motor rotated but the problem is same that move some time reverse some time forward with same connections.

3: Resistance between common (black) to Red lead 13K ohm.
Resistance between common (Black) to Yellow lead 6K ohm.
Resistance between Red to Yellow lead6K ohm.

Regards
Shaheed

 

Shaheed:

4) Your original post said that two leads were connected together, and you labeled them as ‘common’! Were they both Black, or were they different in color?

5) Did you happen to measure the currents when you experimented with 12Vdc and 220Vac?

6) Do you know the approximate age of the motor?

7) Does the Woodward UG-8 Manual mention a 3-wire servo-motor?

Regards, Phil

 

All,

It seems presumptuous to say the motor in question is a "stepper motor". Most of the speed changer motors I've seen on older mechanical steam turbine control systems (such as this seems to be) were simple DC motors, which could be reversed by simply changing the polarity of the applied DC voltage. Here is a link to a www.wikipedia.org article about stepper motors, and I question if the motor in this thread is even a stepper motor.

http://en.wikipedia.org/wiki/Stepper_motor

It seems odd that the motor in question was not previously connected to some control system which was applying voltage (DC or AC) in proportion to a command to increase or decrease speed/load reference by changing the physical position of a lever which can be accomplished with an electric motor. The Woodward manual for the UG-L controller family does not talk at all about any electric motor, so it's not a physical part of the mechanism--just some means of changing a lever position to change speed/load reference.

A lot of DC motors have one lead of the field and one lead of the armature connected together--but only usually if the motor rotates in one direction. Connecting one lead of the field and the armature together would also yield different resistances, as noted by the original poster.

It's just not clear that this is a stepper motor, even though this would be a good application for a stepper motor doesn't mean it is actually a stepper motor.

And, what about the outputs from the control system to this motor? Haven't they been measured/checked using a voltmeter, or the schematics of the control system consulted to determine what the output might be?

As cww said, just connecting a motor across the line could cause serious damage--to the motor and to the personnel observing the results! If this came with a turbine or was found with a turbine, surely there was a control system at some point "driving" this motor and there are (or were) some drawings that could be used to determine what voltage was being applied to the motor leads.

If not, I suggest obtaining a motor that is suitable for the application--and the control system which will be used for the application (if it's not the original control system!). But, there just seems to be a lot of presumptions here, and there should be (or were at some point) a control system connected to this speed/load reference changer motor, along with some drawings. Perhaps the drawings are gone or can't be located, but that doesn't mean the outputs of the control system to the motor can be measured. Or if the control system is being upgraded, usually the company providing the new control system uses the old control system to determine what and how to work with the devices on the turbine.

But something just doesn't seem right here, either with the situation or the presumptions. Without motor nameplate data, or some drawings or some control system output voltages, this is all just very fruitless--and frustrating.

I agree with cww; it may not be (likely is not) a stepper motor, just because that would be a good choice of a motor for this application.

 

Those resistances seem way too high for a stepper, indeed high for any sort of motor I'm familiar with. Is it possible there are (were) drive electronics built in. Awfully hard to help by description.

Regards
cww

 

Hi
Phil Corso,
Curt wuollet,
CSA

Luckily I found some old pages of this motor data that is
AEG SYNCHRONISIERMOTOR
Typenbezeichnung RSM 64VG
Nennleistung 0.002Kw
Nennspannung 220V
Nennstrom 0.045A
Synchronmotor

as per Q4, Ans) Common together leads are (White+Red)

Ans5) The current on AC/DC was too low

Ans6)Age of the motor is about 1960 to 1970

Ans7)No UG8 governor manual not mentioned about motor.

On the 2nd page a connection diagram mentioned Erganzt 16.4.69 Wiring diagram for synchronizing synchronous motor AC operation shows
Connected an unknown capacitor across both winding end leads to (Red + yellow) brought one lead for rev and one for fwd operation. The other both leads of winding common together marked (black) and connected to neutral. These are common split phase ac motor connections.

I used an available capacitor of 2.2uf but the motor behaved same some time fwd and some time rev.

In other operation of 3 phase shows One lead changeable with S phase, connected to R phase coming out from one winding set, while its 2nd lead connected permanent to 0 neutral.

The 2nd winding on lead connected to S phase changeable to R phase while 2nd lead of this set is permanent connected to T phase. This operation not yet checked.

Regards
Shaheed

 

Shaheed... if the motor is indeed a split-phase motor then there are two parallel windings, say, 'Run' and 'Start'! They are distributed around the stator, displaced 90 electrical deg in space, but somewhat less in time.

The Start-winding has fewer turns, but a smaller diameter wire than the Run-winding has, therefore it will have a high-resistance and low-reactance! Conversely the Run-winding has a larger diameter wire, resulting in low-resistance and high-reactance. Starting-torque is developed when the Start-winding current, Is, lags the Run-winding current, Ir! This is usually accomplished by inserting a capacitor, in series, between the Start-winding and the supply!

Let us know if additional info, or a schematic, is required.

Phil

 

Thank you Phil Corso for valued informations.

The motor have been operated in correct directions. There were two separate stators windings and rotor is consist of permanent magnets.

One of our team member connected one 2.2 uf capacitor across one stator winding say winding A. one lead of both stator windings A+B were common and supplied 220VAC to remaining 2 leads of both stator windings. the motor started in fwd direction. Removed capacitor and connected across next stator winding say B winding and supplied 220VAC to remaining 2 leads of both windings. the motor started in rev direction producing healthy torque with rated current. So the problem is solved. I appreciate your cooperation and also thanks to Curt W & CSA,

Regards
Shaheed

 

Shaheed... you are closing-in on the fact that the motor is probably a “Permanent” split-phase motor, that is, both Run and Start-windings have equal or near equal impedances!

If you want I can provide you with a schematic illustrating a Dual-Action (Up/Down, Increase/Decrease, etc) control-circuit using a single capacitor!

Phil

 

That would explain a lot, it behaves like synchronous motor because it is.

If those resistances are correct it's a very low power motor as well.

Regards
cww