Molding machine: 208V vs 240V
Molding machine: 208V vs 240V
(OP)
Mechanical engineer here. I have 8 hydraulic molding presses in my facility for over-molding silicone. We're moving them to a new building that runs 208V power supply. These machines have a call out on the side that says "240V 60 AMP" Can these run safely/efficiently on 208 V or do I need an electrician to amplify this?
I tried contacting the manufacture but they are out of business :( I have a very basic manual, but there is not mention of this anywhere
Thanks in advance for any insight you can offer!
I tried contacting the manufacture but they are out of business :( I have a very basic manual, but there is not mention of this anywhere
Thanks in advance for any insight you can offer!





RE: Molding machine: 208V vs 240V
Also adding Boost tranformers to raise 208 to 230 ..
back in the days when SCE went to 208 v as their standard ....(claimed it saved them a few dollars.... cost their customers a bunch, though!)
One problem that's hidden is that the 208v supplies can sag to 190v when loaded ... further compounding the problem.
If it were me, I'd find an ACME Transformer (or similar) catalog and select the appropriate BOOST transformers to raise the 208 to 230vac.
RE: Molding machine: 208V vs 240V
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RE: Molding machine: 208V vs 240V
RE: Molding machine: 208V vs 240V
You might consider a larger set of transformers to run all the machines.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Molding machine: 208V vs 240V
Yes, there are heaters. We already wait 1 hour for the presses to get hot, so I don't want to wait any longer.
These buck-booster, will I need one for each machine?
http://www.acmetransformerspro.com/acmebuckboosttr...
RE: Molding machine: 208V vs 240V
RE: Molding machine: 208V vs 240V
Contrary to Jeff's (jraef's) comment, NEMA MG-1 2011 and real world experience would disagree.
NEMA MG-1 Section II, Part 14.35 - OPERATION OF 230-VOLT INDUCTION MOTORS ON 208-VOLT SYSTEMS
Induction motors intended for operation on 208-volt systems should be rated for 200 volts.
Operation of a motor rated 230 volts on a 208-volt system is not recommended (except as described in 14.35.2) because utilization voltages are commonly encountered below the -10 percent tolerance on the voltage rating for which the motor is designed. Such operation will generally result in overheating and serious reduction in torques.
NOTE: For every 10 deg. C. rise in operating temperature above rated, insulation life is cut in half ! In like manner, bearing life is also reduced.
Motors rated 230 volts, but capable of operating satisfactorily on 208 volt systems shall be permitted to be labeled "Useable at 200 volts." Motors so marked shall be suitable for operation at rated (1.0 service factor) horsepower at a utilization voltage of 200 volts at rated frequency, with a temperature rise not exceeding the values given in 12.44, item a.2., for the class of insulation system furnished. The service factor, horsepower, and corresponding value of current shall be marked on the nameplate; i.e. "Useable @ 200 V. __________hp, __________amps, 1.0 S.F."
14.35.3 Effects on Performance of Motor
When operated on a 208 volt system the motor slip will increase approximately 30% and the motor locked-rotor, pull-up and breakdown torque values will be reduced by approximately 20-30%. Therefore, it should be determined that the motor will start and accelerate the connected load without injurious heating and that the breakdown toerque is adequate for the application.
Jeff, without knowing the specifics of the given motor(s) design, that's a rather dangerous statement to make.
RE: Molding machine: 208V vs 240V
Badger2011
Here is a link to a PDF file published by ACME Transformer. It contains a treasury of information about Buck-Boost transformers and their application.
I think you'll find the information you need when considering them as a remedy for your situation.
itsmoked and pwrengrds both raised good points to consider.
Regarding itsmoked's comment .... I'd suggest you do a COST - BENEFIT analysis to determine whether or not a new distribution transformer is a better solution than a Buck-Boost transformer for each machine. Your analysis should include not only materials, but cost of installation as well. Also, as you read through the ACME Transformer PDF file linked above, you'll become aware of not only the advantages of the Buck-Boost solution but also the disadvantages as well.
Kind regards,
RE: Molding machine: 208V vs 240V
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Molding machine: 208V vs 240V
go back to my post and you will see that I took umbrage ONLY with jraef's statement : TECHNICALLY, a lot of 230V rated motors can safely run at 208V,
which I placed in Quotes .... I have no quarrel with the remainder of his post; only with that statement which I, and NEMA disagree completely with.
His statement lacks foundation and appears to be opinion based as opposed to FACT based.
Do you believe that "Technically" a lot of 230 volt motors can SAFELY run at 208V ?
That's what he said; that's what I challenged; and NEMA concurs : "Operation of a motor rated 230 volts on a 208-volt system is not recommended..."
NEMA did NOT say: "Technically a lot of 230 volt motors can SAFELY run at 208V."; that's what Jeff said, and it's simply not true.
RE: Molding machine: 208V vs 240V
Many of us disagree with your statement that "it's simply not true."
230 Volt motors should be capable of operation on 208 volts according to NEMA.
That's the voltage at the motor.
On a 208 Volt SYSTEM the voltage at the motor may be below 208 Volts and that is why both jraef and NEMA recommend that 230 Volt rated motors NOT be used on 208 Volt SYSTEMS.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Molding machine: 208V vs 240V
Sheesh...
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies