need help starting an AC motor

[shess]

Hi, I'm trying to get an AC motor going but have been unable to do so. Here's the setup: it is the force feedback motor from an arcade machine and I'm trying to retask it. There isn't any good info on the motor case and I've been unable to find any more detailed specs about it. After looking at a schematic of the game, I can see that the motor drive board takes in 100VAC / 6.5A and after receiving instructions from the game, sends it out to the motor. The motor itself has 3 power wires coming out of it and one has a white blank label wrapped around it, so I'm assuming there's no AC->DC conversion happening on the board. The motor casing itself is sealed so I don't know if there's a start/run cap inside but there are 2 large capacitors on the drive board (680uF/250V).

Here's what I've tried and the results. Without power being applied, the shaft spins freely and since it's a force feedback motor, it should be able to spin in reverse. From the transformer I connect both AC lines into 2 of the leads on the motor, leaving one empty. The motor hums and jerks a bit, but doesn't start. The shaft doesn't spin freely anymore and turning it doesn't get it started. Moving the wires to different positions on the motor connector doesn't change anything.

Then I found something that says I should put a capacitor in series between two of the windings to introduce a phase difference. So, one AC wire goes to a motor wire and then the other is switched between two wires connected to the motor with a capacitor connected to both lines. Applying the other AC wire to either wire does the same thing as before, no spin and it resists turning.

Finally I tried hooking up the AC wires directly to the wires with the capacitor in series to two of the motor leads. The shaft slowly and briefly starts to spin before the fuse (10A fast blow) between the wall and transformer blows. I noticed the capacitor was also very hot to the touch after this and not with the other tests.

So...how can I get this motor started and how do I get it to change direction?

Thanks,
Scott

 

[Diver300]

Post a photo.

Measure all the resistances between the connections and post them.

 

[shess]

Photo of the motor or just an MS Paint drawing of the connections? I checked the resistance between the wirings and I get about 92 Ohms between all the pins.

Scott

 

[tcmtech]

Most likely its a three phase motor and the circuit board is a simple three phase variable frequency driver of some sort.

 

[RODALCO]

3 phase motor

Please post a photo of the motor and the nameplate Voltage Amps and kW rating.

From your comments it looks like a 3 phase motor as tcmtech also suggests.

It can run on 1 phase with a capacitor provided that it is switched off after the motor is up to speed.

For 120 Volts AC , a capacitor of at least 200 Vac must be used to allowe for a safety margin.

I run succesfully a rotary converter at my home on 1 phase 230 Volts and "generate" 400 Volts 3 phase from it while running of a 16 amp MCB.

 

[shess]

This motor came out of an arcade so it was designed to run off single phase power. Can a motor drive board convert single phase power to 3-phase power? The nameplate doesn't have anything to identify the specs of the motor, I had to look at a wiring schematic of the game. On the diagram it says the transformer outputs 100VAC at 6.5A. I saw nothing written that would indicate the kW rating. Here are links to the pictures.

**broken link removed**
**broken link removed**

There are two pots on the back. One is for the steering wheel. The other is for the motor, presumably for feedback to the motor control board.

Scott

 

[RODALCO]

A motor control board can convert single phase power into three phase power.

It basically rectifies and filters 1 phase to DC.

Then by means of a controlled three phase bridge, it switches the DC voltage into three phase 120 degrees phase shift power to drive a three phase motor.

Most motor soft starters and speed controllers are based upon a similar principle.

It is hard to determine from your motor if it is 1 or 3 phase.

Can you make a photo of the connection block please ?

Your transformer 100 V 6.5 A yields 650 VA or 0.65 kW.

What is the schematic about in the second picture ?

 

[shess]

If you look on the side of the motor you can see the 3 black wires going into the casing. That is the only view of the power connection. Since it was designed for one single purpose, Sega didn't see fit to give much info on it. Here's a picture of the control board that is supposed to drive it (not mine): **broken link removed** .

Those large caps are 680uF 250V. The schematic I was referring to only shows that the three power leads go from the motor to the control board and the input power to the board is 100VAC.

Scott

 

[shess]

Since the motor did start turning briefly when I had two of the motor wires hooked directly to 100VAC with a capacitor in parallel, is there a way I can use this setup without it blowing a fuse? Maybe a larger capacitor?

 

[Diver300]

The normal setup would be to connect a capacitor between two of the motor leads. Connect neutral to the third lead. Then connect live to one of the leads that also has a capacitor connected and the motor should spin

However, you said:-

The shaft doesn't spin freely anymore and turning it doesn't get it started.

which isn't what I would expect if the motor were a simple 3-phase induction motor. They will usually spin with no load on single phase, once they have been started.

You could try spinning it by hand and seeing if any voltage is generated. If the is voltage, it almost certainly isn't a simple induction motor.

 

[crutschow]

Could it be a stepper motor?

 

[shess]

As far as I can tell, there is no gearing inside the motor. This motor is for use with a steering wheel so it has a bar on the shaft that limits its rotation to not quite a full circle. It uses a potentiometer on the back to act as a servo I guess; it tells the controller board the position of the shaft.

I'll check to see if any voltage is produced by just spinning the shaft.

Looking at the picture of the controller board in one of my earlier posts, **broken link removed** , any idea what the two large capacitors are for? There also seem to be 3 small toroids near the header for the motor output. That header has 4 pins, 3 for the motor and then one for a separate ground.

Ultimately, I plan to do the same thing as this guy, http://forum.arcadecontrols.com/index.php?topic=94653.0 . But unfortunately, I've been unable to contact him.

Scott

 

[shess]

So with the multimeter set to VAC I hooked up to two of the motor leads. After spinning the shaft as fast as I could, I got it up to about 66V. The result was the same regardless of how I hooked up the multimeter to the 3 motor wires. I then switched to VDC and after spinning the shaft it would go from neg to pos 12V even though the wheel was spinning in one direction.

Does that help figure this thing out?

Scott