Variable Transformer Question

[Ceilingwalker]

Good day all. I have a Powerstat Variable Transformer that I picked out of the garbage and have been playing with. Looking at the diagram on the front of it, it appears as though input goes hot to terminal 5, common terminal 2, and terminal three appears to be the varying voltage. My question is, why is it that my meter reads voltage on terminals 1, 3, and 4 when I touch only one lead ( red or black ) to it? The voltage is different between the red and black, however, they both still register a + voltage. Thank you.

 

[Reloadron]

You don't mention a model number on the name plate. Is it like any of these units?

 

[KeepItSimpleStupid]

It may be a phantum voltage. The transformer and the wires in the house are radiating 50 or 60 Hz. Your body and the leads of your meter are acting as antenna and picking this up. This is generally due to the fact that the input impeadence of the meter is high.

Dangle one lead and touch your skin as an experiment.

 

[Ceilingwalker]

Sorry guy's. It's a Powerstat 116BU.

 

[Diver300]

Connect a lightbulb, a simple one not a compact fluorescent or anything with a transformer, to your variable transformer. That will take enough current so that there will be no phantom voltages.

All the variable transformers that I have seen are auto-transformers, so that the neutral of the load is connected to the neutral of the supply and the neutral of the transformer.

 

[Reloadron]

This link should help as the 116 BU should have been replaced by the 116 CU model. The link covers all the possible setups that can be used.

As to your readings? Likely, as was mentioned just noise you are picking up.

I have a few around here somewhere. Good units and they can come in handy. Hope the link helps.

Ron

 

[sivakumar97]

Powerstat variable auto transformer Type EMT6245P

I test 36-48VDC Drive motors through a forklift controller powered by a 36V Battery. I picked up the above transformer so I can do away with the battery.(it is taking up space and I do not use too much). The transformer comes with a drive motor SS150P2 made by slo-syn. Eventhough the tag says the type the rest of the information is not visible at all. I do not have a wiring diagram or manuel either.

Does anyone has more info. how to hookup or will this work for my purpose? The guy said it is 3phase but nothing on the tag.

 

[crutschow]

I test 36-48VDC Drive motors through a forklift controller powered by a 36V Battery. I picked up the above transformer so I can do away with the battery.(it is taking up space and I do not use too much). The transformer comes with a drive motor SS150P2 made by slo-syn. Eventhough the tag says the type the rest of the information is not visible at all. I do not have a wiring diagram or manuel either.

Does anyone has more info. how to hookup or will this work for my purpose? The guy said it is 3phase but nothing on the tag.

You do realize that the transformer outputs AC and you will need to add a bridge rectifier (and possibly a filter capacitor) to drive a DC motor (?).

 

[Reloadron]

I test 36-48VDC Drive motors through a forklift controller powered by a 36V Battery. I picked up the above transformer so I can do away with the battery.(it is taking up space and I do not use too much). The transformer comes with a drive motor SS150P2 made by slo-syn. Eventhough the tag says the type the rest of the information is not visible at all. I do not have a wiring diagram or manuel either.

Does anyone has more info. how to hookup or will this work for my purpose? The guy said it is 3phase but nothing on the tag.

Based on the information provided there is no way to help. You don't mention the KVA rating of the transformer. You do mention 3 phase but not if it is 3 phase wye or delta power you will be using. As Carl mentioned you will need a rectifier for the transformer output.

Slo-Syn makes several motors used on variable transformers including stepper (which require a stepper driver) and a few variations of synchronous AC motors using phase shift for forward and reverse. They also use micro-switches for limits.

Looking at the Slo-Syn (Superior Electric) web pages I would venture the model you have is older, you may want to email or contact them with the part number for the manual.

You don't provide the name on the data plate for the transformer?

Ron

 

[sivakumar97]

Thanks Carl and Ron. The only info. on the name plate is the Type EMT6245P. I am trying my best to get some information from Superior Electric (Powerstat) but looks like hitting a dead end.

I am not an electrician, however I will defintly get a qualified electrician to work on this project. I will get a bridge rectifier and filter capacitor, no problem. Any spec.? The guy who sold to me said 3P 600VAC .Is there a website that gives step by step instructions to hook this kind of autotransformer to convert AC to DC? The tech. at superior said it will take weeks to get the information, as they are too busy.

 

[Reloadron]

Assuming you be driving the transformer with the correct 3 phase power rectifying the output to DC will not be difficult. You only need a 3 phase rectifier or 6 individual diodes that will handle the voltage and current.

Using discreet diodes it would be configured like the attached. Ignore the colors I used at the inputs as the drawing was left over from something else. Also the drawing does not include a filter capacitor which may be needed.

I just wish more was known about the transformer(s) and the motor drive.

Ron

 

[sivakumar97]

Powerstat variable transformer EMT6245P

Hi Ron

Today, I received the following info. from powerstat:

The EMT6245P was a special POWERSTAT® Variable Transformer used in an Automatic Voltage Regulator product and did not have any official end user specifications. You can however use it as a Variable Transformer with the following ratings:

Input: 120 volts, 50/60Hz, terminals #4 and #1

Output: 0 - 120 volts, 45 amps max, terminals #3 - #1

 

[Reloadron]

OK we have a few conflicts here:

The guy who sold to me said 3P 600VAC .

The guy who sole it to you said it was a 3 phase 600 Volt variac transformer. However, the guys who built it provided this information:

Input: 120 volts, 50/60Hz, terminals #4 and #1

Output: 0 - 120 volts, 45 amps max, terminals #3 - #1

Now if it is a three phase variac you will have three very large variacs stacked with a motor drive usually on the top of the pile. The shafts will be coupled. Even though as you mention it was a custom unit a three phase 120 volt 45 amp variac would be unusual. Generally speaking 3 phase units come in 240 and 480 volt inputs. If this is a 120 volt 3 phase unit and you do not have three phase 120 volt power available to you then you have your work cut out for you. So is it a three phase unit?

Next, if this is 3 phase do you have three phase power available and if yes, is it a wye or delta configuration?

Regardless of voltage a 45 amp variac will require as a minimum 50 amp service which will require AWG 6 bus drop cable.

Ron

 

[sivakumar97]

Hi Ron

Here are some pictures of the transformer. I will check with the guy who sold it to me.

Thanks

 

[Reloadron]

Thanks for the pictures. Yes, you have a 3 phase variac. Pretty typical. I also see the capacitor hanging out there for the motor reversing circuit as well as at least one micro-switch (limit travel switch). They are large and they are heavy. I have several really large ones at work. If you go back in this thread I gave a link based on the original post. Your pin out (the connections) are the same as one example in the link. Let me attach a few images.

Now in your pictures I also see a small power transformer, I'll venture a guess that provides the power for the motor. This is interesting as the manufacturer said it was a 120 volt variac but if that were the case there would be no need to use a transformer for the motor drive.

We are going to need to know what power you have available as to 3 Phase. Voltage and configuration.

Ron

 

[sivakumar97]

I did receive the following message from Powestat.

My apolagies. The ratings I gave you were the ratings for each deck. That was how it was used in the unit it was stripped from.

If connected with all terminals #1 connected together and to neutral, while terminals #4 are the hot of A, B and C phase, the unit can be used for an input of 208Y/120 (208 line-line & 120 line-neutral) or 240Y/138. The max output will match the input and be rated for 45 amps.


The transformer must be the auto transformer which stepped the input line-line voltage down to the motor voltage of 120 volts.

 

[Reloadron]

OK, no problem and all you need is 3 phase power. Got that? They ran 3 phase Y (WYE) configuration. What he told you makes enough sense.

Ron