Problems with hydrolic metal shear

[Alex electrical student]

Figure this one out. I hooked up a 3 phase power supply to a metal shear. 30 A disconnect is connected to a bus duct. From there i installed a so cord that went down to about 4 ft. from the floor. It had a three phase cord end on it so that the metal shear could be unplugged. From there it went into the motor starter.
I wired it up and it didn't work. It made some noses but it didn't move any hydrolics. What was the problem.

 

[mdshunk]

What's the rotation like? Are the cord caps properly terminated?

 

[captaincrab55]

What voltage was the motor wired for?

 

[Alex electrical student]

I wired the cord ends corectly. It's wired to 208 V 3 Phase. I checked the cord ends with my meter and got 211V in between the phases and 121V from phase to ground. It doesn't have a neutral.

 

[mdshunk]

But.. but... but... did you check the rotation yet? If the pump's going backwards, you're not gonna get much work done.

 

[captaincrab55]

I wired the cord ends corectly. It's wired to 208 V 3 Phase. I checked the cord ends with my meter and got 211V in between the phases and 121V from phase to ground. It doesn't have a neutral.

Is the Motor wired for 208 Volts?

 

[thinfool]

Did you push the overload reset on the starter? If this is a new machine, it is not rare for the overloads to either be tripped, or they were never set when the heaters were installed in the first place.

Are there any other safeties on the hydraulic unit?

Lots of possibilities here.

 

[Rick Christopherson]

You said the system made noise, but had no hydraulic power. By this, and your last posting, I would assume that you heard more than just a hum from the motor. If it was just a hum, then you would have dropped a phase. However, your voltage readings indicate this is probably not the case.

As Marc suggested, there is a good chance your hydraulic pump is rotating backward. When this happens, you will not develop hydraulic pressure, and none of the systems will operate.

I am guessing that you may not be very familiar with 3-phase motors, but if you do not have the proper phase rotation on the connections, the motor will run backward. To correct this, simply swap any two motor leads. It doesn't matter which two you swap, the result will be the same, and the motor will turn in the opposite direction.

If this doesn't work, then you need to make sure you don't have a dual voltage motor configured for 480 volts. You can check this by looking at the lead configuration inside the motor's junction box.

 

[Alex electrical student]

You got it. It's the phase rotation. I didn't have a phase rotation meter with me to check the phase rotation. Onence i switched two phases it started working properly. For hydrolics it's important two have phase rotation in proper way.

 

[mdshunk]

I didn't have a phase rotation meter with me to check the phase rotation.

Wouldn't have mattered anyhow. Clockwise on my phase rotation meter might be counterclockwise on yours. The machine might have a sticker that shows a certain rotation, but you don't know if they're talking about facing shaft end or what.

The phase rotation meter is more useful for panel changes or machine moves. Check and mark down the phase rotation before your start your work, and recheck it again before you energize your new work to make sure it's the same.

 

[emahler]

maybe it's a bad bus duct?

 

[mdshunk]

Onence i switched two phases it started working properly.

May I ask why you're doing this work, anyhow? Is this a project for your class? Co-op job? Here we are at 9:00 on a Saturday night when you switched the phase order and got it working, and that concerns me.

 

[Alex electrical student]

I did this couple of days ago and i figured it out 5 minutes later. I posted it to see how many people know how important the phase rotation is. And yes this machine is in college. We have bus ducts hanging overhead in every shop. We had to wire all the welders, lathes, wood working machines and whole bunch of other stuff.

 

[mdshunk]

I posted it to see how many people know how important the phase rotation is.

So you really didn't need help?

PM me with your name and address so I can send you a bill.

You must know that these sort of quiz exercises are fine if you let people know upfront that it's just a quiz. If you make it seem like you need help, then it's discovered that you were just quizzing, that ticks people off.

 

[iwire]

I did this couple of days ago and i figured it out 5 minutes later. I posted it to see how many people know how important the phase rotation is.

Good way to make friends. :roll:

Now what is phase and rotation? :roll:

 

[Alex electrical student]

So you really didn't need help?

PM me with your name and address so I can send you a bill.

You must know that these sort of quiz exercises are fine if you let people know upfront that it's just a quiz. If you make it seem like you need help, then it's discovered that you were just quizzing, that ticks people off.

I'm broke right know. I'm going to college full time so i haven't work for past three months.
Someday when ill get rich i will send you a nice tip. :smile: :smile: :smile:

View attachment 1259

For now i will at least send you an image of one:smile: :smile: :smile:

 

[Alex electrical student]

Phase rotation is in what sequence the phases follow each other.

1 is for phase A
2 is for phase B
3 is for phase C

Forward rotation
View attachment 1260

Reverse rotation
View attachment 1261

This is why it takes only to switch 2 phase wires in between them selves to change the rotation.

1,2,3 is your forward. Switch 1 with 2 You get. 2,1,3

See these are all reverse rotations (2,1,3) (3,2,1) (1,3,2)

forward rotations (1,2,3) (2,3,1) (3,1,2)


If i'm wrong correct me please.

 

[Controls]

Mdshunk gave you good information. Here is a few more :
A-when you gain more experience, by looking at the mechanical design of certain equipmet, such as hydraulic pumps etc. you may have a better chance of guessing which way a pump/motor should turn, If nothing is marked or you have no tools to verify the correct direction. You will see where the discharge piping, where the inlet piping is and make a decision based on that. Like , I said it comes with experience.
B-If an hyraulic pump is turning in the wrong rotation: chances are cylinders, slides... may move or stroke in the wrong direction too as soon as you turn on the motor. Of course, this still depends on the type of the valves used.

 

[Alex electrical student]

Here is the shear i had to wire up
View attachment 1265
It is totally enclosed. You don't see the motor or the pump. All you have open is the motor control on the bottom left corner.

With this metal shear there was no harm from wiring it in reverse but in other places like conveyor that can only turn one way and if you hook up the motor in reverse the conveyor will go backward and make a big mess. Then the factory will be down for a week. Have to be sure you got it hooked up correctly from the first time.

 

[mdshunk]

That's not even a shear! That's a punch press, sometimes called an "ironworker".