I recently looked at a printing press which is rated 230volts, 3 phase. The voltage at this fascility is 3 phase, 4 wire 240volts with a grounded center leg. The actual measured voltage is around 246 to 248 volts. I was wondering if this warrants the need for a buck transformer or will the equipment be okay without it. This press is fairly basic, no electronics, just two motors and a 120v xfmr for the controls. Thank you.
Is a buck transformer needed ???
- Thread starter patc
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Re: Is a buck transformer needed ???
Unless the press manufacturer specifically states that 230v is need exactly I would conclude that you don't need any adjustment. Most equipment is designed to run just fine on their nameplate voltage +-10%. You may find that after you apply the press load in the circuit the voltage will drop closer to the 230v.
Unless the press manufacturer specifically states that 230v is need exactly I would conclude that you don't need any adjustment. Most equipment is designed to run just fine on their nameplate voltage +-10%. You may find that after you apply the press load in the circuit the voltage will drop closer to the 230v.
stew
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- federal way,washington
Re: Is a buck transformer needed ???
NEMA allows a motor to run at full hp and torque when at 10%+or - in voltage . 230 + 10% = 253. Never had a problem with this at 240 0r 248 and you should work just fine also.
NEMA allows a motor to run at full hp and torque when at 10%+or - in voltage . 230 + 10% = 253. Never had a problem with this at 240 0r 248 and you should work just fine also.
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Re: Is a buck transformer needed ???
Connecting a 230 volt rated motor to a 240 volt system looks like it violates this.
NEMA yes but does the NEC?
Connecting a 230 volt rated motor to a 240 volt system looks like it violates this.
I am not saying it will not work but is it code compliant?
Re: Is a buck transformer needed ???
I think your press is probably intended to be connected to 240V. You are probably reading 230V from the current requirements (i.e. XXX amps at 230V.)
I have never heard of a piece of equipment actually designed to be connected to a 230V source, because that is not one of the standard voltages in the U.S. 208V and 240V are standard.
Current draws for 240V motors are listed at 230V because it is assumed there will be some voltage drop between the source and the motor. The rated current at 230V is actually a little higher for a motor than the current at 240 V (for the same power out). Thus it is safer to size the wiring and breakers, ect for 230V.
Steve
I think your press is probably intended to be connected to 240V. You are probably reading 230V from the current requirements (i.e. XXX amps at 230V.)
I have never heard of a piece of equipment actually designed to be connected to a 230V source, because that is not one of the standard voltages in the U.S. 208V and 240V are standard.
Current draws for 240V motors are listed at 230V because it is assumed there will be some voltage drop between the source and the motor. The rated current at 230V is actually a little higher for a motor than the current at 240 V (for the same power out). Thus it is safer to size the wiring and breakers, ect for 230V.
Steve
stew
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- federal way,washington
Re: Is a buck transformer needed ???
iwire. And just how does this violate the code. We are talking about connecting the motor for a higher voltage not a lower voltage. Int the case of lower voltage the does lie problems. Especialy when motors rate 240 volts are connected to 208 volt systems.In that case you have a 240 volt motor which is NEMA rated to operate at a minimum of 226 volts before overheating would occur and it also would violate code at that point. I dont even like to see 230 volt motors operate of 208 systems because the 10% gets you down to 207 which is just too close to the (actually 1 volt lower) than the NEMA maximum alowwable. also if you look in definitions under Voltage Nominal It says in part that the nominal voltageis one which conveniently designates the voltage class. "The actual voltage at which a circuit can operate can vary from the nominal within a range that permits satisfacory operation of equipment." I believe thats wher the code by reference allows cicuits to operate knowing the voltage drop is below the connected voltage. 90.7 refers also to the organizations which test and certify equipment for safe usage NEMA being one. They also refer you to the definition of listed which again refers to these qualified organizations. In our State the UL and NEMA are specifically referrred to along with NEC in the law which governs which standards shall be used. I do not believe that if a motor is operated within the voltage differential that NEMA specifies that it would become a code violation.
iwire. And just how does this violate the code. We are talking about connecting the motor for a higher voltage not a lower voltage. Int the case of lower voltage the does lie problems. Especialy when motors rate 240 volts are connected to 208 volt systems.In that case you have a 240 volt motor which is NEMA rated to operate at a minimum of 226 volts before overheating would occur and it also would violate code at that point. I dont even like to see 230 volt motors operate of 208 systems because the 10% gets you down to 207 which is just too close to the (actually 1 volt lower) than the NEMA maximum alowwable. also if you look in definitions under Voltage Nominal It says in part that the nominal voltageis one which conveniently designates the voltage class. "The actual voltage at which a circuit can operate can vary from the nominal within a range that permits satisfacory operation of equipment." I believe thats wher the code by reference allows cicuits to operate knowing the voltage drop is below the connected voltage. 90.7 refers also to the organizations which test and certify equipment for safe usage NEMA being one. They also refer you to the definition of listed which again refers to these qualified organizations. In our State the UL and NEMA are specifically referrred to along with NEC in the law which governs which standards shall be used. I do not believe that if a motor is operated within the voltage differential that NEMA specifies that it would become a code violation.
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- Massachusetts
Re: Is a buck transformer needed ???
Gee Stew take it easy, I just pointed out a code article.
The name plate on the press says 230 volt, the system he wants to connect it too is a 240 volt system.
110.4 tells us The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.
I do know about the 10% I am just asking where is the code article that lets us bypass 110.4?
Just a simple question.
Gee Stew take it easy, I just pointed out a code article.
The name plate on the press says 230 volt, the system he wants to connect it too is a 240 volt system.
110.4 tells us The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.
I do know about the 10% I am just asking where is the code article that lets us bypass 110.4?
Just a simple question.
stew
Senior Member
- Location
- federal way,washington
Re: Is a buck transformer needed ???
and my simple answer is 90.7 allo0ws it in my humble opinion
and my simple answer is 90.7 allo0ws it in my humble opinion
- Location
- Massachusetts
Re: Is a buck transformer needed ???
The reason I ask is this, in this area we must use equipment with a tag that says 208 or 208-230 for connection to 208 systems.
Equipment with this marking of 230 would fail inspection [110.3(B)] if connected to 208 volt.
The problem is this leaves no room for voltage drop, you are already at the bottom end of the limit.
I never have said it will not work.
Bob
[ April 07, 2004, 05:29 AM: Message edited by: iwire ]
The reason I ask is this, in this area we must use equipment with a tag that says 208 or 208-230 for connection to 208 systems.
Equipment with this marking of 230 would fail inspection [110.3(B)] if connected to 208 volt.
230 - 10% = 207 volts so 208 is within the 10%
The problem is this leaves no room for voltage drop, you are already at the bottom end of the limit.
I never have said it will not work.
Bob
[ April 07, 2004, 05:29 AM: Message edited by: iwire ]
stew
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- federal way,washington
Re: Is a buck transformer needed ???
why would it fail if connected to a 208 volt system if it was inastalled per the instructions which say it can be installed if it is within the nemea tolerance?
I wouldnt do it either but I fail to see why it is a violation. Voltage drop is of course a problem but not within the purveyence of the inspector I dont believe but rathe a design and application issue.
[ April 07, 2004, 01:18 PM: Message edited by: stew ]
why would it fail if connected to a 208 volt system if it was inastalled per the instructions which say it can be installed if it is within the nemea tolerance?
I wouldnt do it either but I fail to see why it is a violation. Voltage drop is of course a problem but not within the purveyence of the inspector I dont believe but rathe a design and application issue.
[ April 07, 2004, 01:18 PM: Message edited by: stew ]
G
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Re: Is a buck transformer needed ???
Edit in progress
[ April 07, 2004, 01:51 PM: Message edited by: bennie2 ]
Edit in progress
[ April 07, 2004, 01:51 PM: Message edited by: bennie2 ]
stew
Senior Member
- Location
- federal way,washington
Re: Is a buck transformer needed ???
Bennie I beg to differ. The 10% is taken from the nameplate voltage not the nominal applied voltage. This is the standard that NEMA uses and they refer only to the nameplate voltage to get the tolerance. Thus 240 volt motors may be used at a minumum of 216 and 230 volt motors at 207 and 220 volt motors at 198 and 200 volt motors at 180 etc.
Bennie I beg to differ. The 10% is taken from the nameplate voltage not the nominal applied voltage. This is the standard that NEMA uses and they refer only to the nameplate voltage to get the tolerance. Thus 240 volt motors may be used at a minumum of 216 and 230 volt motors at 207 and 220 volt motors at 198 and 200 volt motors at 180 etc.
G
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Re: Is a buck transformer needed ???
I stand corrected. I didn't edit my post fast enough. I was thinking backwards.
I stand corrected. I didn't edit my post fast enough. I was thinking backwards.
stew
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- federal way,washington
Re: Is a buck transformer needed ???
Sorry I was so quick on the trigger kemo sabe!
Sorry I was so quick on the trigger kemo sabe!
G
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Re: Is a buck transformer needed ???
Hello Ronald: My information from the American Electricians Handbook, indicates that plus or minus 10% of nameplate rating is permitted, but only for short times.
A continuous running motor, should have the nameplate voltage rating at the terminals.
Hello Ronald: My information from the American Electricians Handbook, indicates that plus or minus 10% of nameplate rating is permitted, but only for short times.
A continuous running motor, should have the nameplate voltage rating at the terminals.
stew
Senior Member
- Location
- federal way,washington
Re: Is a buck transformer needed ???
yup
yup
stew
Senior Member
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- federal way,washington
Re: Is a buck transformer needed ???
bennie that is at odds with The Nema recommendations and tolerance which allows full hp and torque to obtained continously at the lower voltage without exceeding the temp rise of the motor.
bennie that is at odds with The Nema recommendations and tolerance which allows full hp and torque to obtained continously at the lower voltage without exceeding the temp rise of the motor.
Re: Is a buck transformer needed ???
We have gone around full circle and are back at the +-10. How likely would it be that one would always have a consistent and reliable voltage that would be the same as the NP voltage? Even in a nominal 480y/277, 460v motors are commonly applied.
But that's NEMA rated motors. But how about motors made to another standards if any?
We have gone around full circle and are back at the +-10. How likely would it be that one would always have a consistent and reliable voltage that would be the same as the NP voltage? Even in a nominal 480y/277, 460v motors are commonly applied.
But that's NEMA rated motors. But how about motors made to another standards if any?
G
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Re: Is a buck transformer needed ???
NEMA Standards Publication MG 1-1993 states; A 10% decrease in voltage, over a period of time, will greatly accelerate the deteriotation of the insulation. Such operation will generally cause overheating and a reduction of torque.
NEMA Standards Publication MG 1-1993 states; A 10% decrease in voltage, over a period of time, will greatly accelerate the deteriotation of the insulation. Such operation will generally cause overheating and a reduction of torque.
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