Meat Grinder with 208V 3 Phase motor 1

[surbani]

I purchased a meat grinder and had the option to set the voltage at either 208V 3 phase or 220V 3 phase, we chose 208V.

The problem is we have recently moved to a new location and now have 220V 3 phase service. What can we do to fix this? Is there a way to reset the voltage in the grinder? Or can we use a transformer?

Thank you!

 

[waross]

You need a pair of buck boost rated 240:36 Volt transformers.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Sorry, hit submit too soon.
With an auto transformer connection the magic of multiplication works for you.
The ratio of a 240:36V transformer is 6.667:1, call it 7:1.
The 36 Volt winding must carry the full 6.5 amps plus 1/7th to excite the 240 Volt winding.
Round it off to 7.5 amps.
7.5 Amps times 36 Volts equals 270 Volt Amps. Nearest size is 500 Volt Amps.
You need two 500 KVA, 240:36 Volt transformers that are buck/boost rated.
240V + 36V = 276V
276V /240V = 1.15
240V / 1.15 = 208.7 Volts
You will use an open delta auto transformer connection.
You may connect the transformers between the motor contactor and the motor overload devices. The motor will be protected and the transformer will only be energized when the motor is being used.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[surbani]

The 220V machine manufacturer says that 240V will not work. That it is too high even though it is within the 10%.

Is there any way we can transform 240V to 220V? for 6.5Amps draw?

Thank you for your help BIll.

If you are ever in BC you should stop by

http://www.moccia.ca

 

[waross]

Same solution, different transformers.
Buck boost rated 240:24 volt in open delta auto transformer configuration will drop 240 Volts to 218 Volts. Two transformers, 500VA each.
We used to service a plant that was part 480 Volts and part 600 volts.
The main service had a pair of auto transformers to drop the 600V to 480V. There was always machinery being moved, often from the 600V area to the 480V area or vice versa. We used a pair of small dry type transformers at each motor that needed a voltage adjustment.
I have done this before and it works well. It saves a lot on transformer costs.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rockman7892]

Bill

Do you have a schematic showing how these transformers would be connected?

 

[surbani]

There is no neutral. The electrician was very surprised to see this...said he has only seen it once before (240 3ph no neutral)...years ago at a sawmill in quebec.

 

[jraef]

Most catalogs provide the information you need to connect it. Example: If you look at page 6, I would go with the 225-240V so you have some head room for voltage drop.

http://www.jeffersonelectric.com/s3/site/catalog/buckBoost.pdf

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[surbani]

I just don't know if it is in open delta or wye...how can I find out?

 

[waross]

I just don't know if it is in open delta or wye...how can I find out?
It doesn't matter if there is no neutral, but look at the transformers. If the secondaries appear to be connected in series it's delta.
That's great, jraef. I blew the size calculation. You can go down to 150 VA x 2. That's a lot cheaper than the 2500 Va your electrician wanted to install.
Back to wye or delta. With a three transformer bank, wye will have one secondary terminal of each transformer connected together and a phase conductor from the other terminal of each transformer. Delta secondaries will be connected in a series ring with a phase conductor taken from each jumper from one transformer to the next. In some cases, two phase conductors may be physically connected to opposite terminals of the same transformer, but even so there will be one phase conductor from each jumper.
With wye, the common terminal is the neutral or the grounded conductor.
With a delta bank, the center terminal of a 120:240V transformer may be used to ground the system.
But, if there is no neutral, it doesn't matter.
Probably delta. A 240 Volt wye requires 139 Volt transformers. They are not common.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

I'd think it is delta. It would have been a 208V/120V service if it was Y connected. Utility probably just used 3 x 120V:240V single phase transformers connected delta. Otherwise, they would have needed special transformers and besides, the 139V line to neutral is useless so why install it?

If they used 3 x 120V:240V transformers they they might have fed a 120V panel from the same service transformers so look for a lighting panel that is fed from the same service. If so, the neutral is the middle point of one of the delta connected transformers. It was mentioned above. If you measured each phase to ground you would read 120V, 120V and 208V for this type of connection.

 

[stevenal]

"The 220V machine manufacturer says that 240V will not work."

Unless it is a very old piece of equipment (1960s or before), this seems suspect. And even then, the 220 rating was intended for both 208 and 240 V services. 220 does not match any modern standard nominal utilization or service voltage. ANSI C84 utilization voltages are 200 or 230, corresponding to service voltages of 208 and 240. Applying a little too much voltage is generally better than too little, since motors will draw less current and run cooler and more efficiently at higher voltage. I would try it without the buck transformer.

 

[waross]

You have three choices if the nameplate says 220 volts.
1> It's over 50 years old.
2> It is an older (pre-harmonization) IEC motor for 50 Hz.
3> It was made in China.
Check to see if it is 50 Hz.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[surbani]

It's a japanese machine, new, and they said it will RUN on 240 but develops vibration. It is an encrusting and forming machine so apparently that vibration causes it not to work properly.

 

[stevenal]

So return it and ask for a machine suitable for use in North America.

 

[ccjersey]

Would a VFD be a good option here? Can you set the maximum voltage output lower than the input from the line?

It sounds as if a frequency difference might be part of the problem with the machine vibrating/not operating properly. I cannot think of any reason it would tend to vibrate when exposed to higher than normal voltage.

 

[edison123]

Take the motor to a motor repair shop and ask them run it at voltages from 200 to 250 V and measure the corresponding no-load currents and vibrations. If either the current or the vibration increases drastically, time for a new motor rated for your [highlight]measured site voltage[/highlight], not some nominal voltage.

I recently had a case where a 4.5 KW motor whose vibration would increase with the voltage (via an stepless auto). I located the problem to the shaft loose in the rotor core to the tune of 0.15 mm. With a new shaft with proper fit, the vibrations went away.

It's time you brought in a good motor repair shop.

Muthu

http://www.edison.co.in

 

[waross]

Excellent suggestion ccjersey. You may have to add some filtering if the motor is not invertor rated.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[stevenal]

Surbani did not say the motor will vibrate, he said the machine will. My assumption is that the higher speed (lower slip) at the higher voltage will cause the unbalanced mechanical load to cause excessive vibration in the machine. Perhaps the frequency adds to this problem as well.

Again I say he needs a machine (including the proper gearing) suitable for NA voltage and frequency. A VFD is a possible solution, but why should he need to pay extra to make a new piece of equipment work?

 

[surbani]

edison123: the problem is the machine has five motors not one. i have attached electrical drawings.

stevenal: I agree with you that the machine should be suitable for NA freq and V, but it is at 60hz and they don't seem to understand. they say that 208V will work, but 220 is ideal. there is a hell of a language barrier even though they are only in irvine, ca. please see the attached drawings, and accept my thanks.

 

[surbani]

scan 2