300V Motor Full Load Current.
- Thread starter bassil
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- Mission Viejo, CA
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- Professional Electrical Engineer
Re: 300V Motor Full Load Current.
I suspect the motor(s) you are describing are either not for US domestic use or are for "specialty" applications.
Especially for low voltage applications, Art 430 "leans" very heavily toward NEMA "standard" motors. (Certain nameplate requirements in 430.7 definitely reflect NEMA and not foreign standards) While NEMA MG-1 recognizes both 50 & 60 Hz, it does not recognize non-standard voltages.
Table 430.150 is based on the highest FLA for any standard motor size that any NEMA manufacture makes. This permits general interchangeability of NEMA motors of the same HP and frame size without requiring the entire installation to be ?re-engineered.? It also provides a relatively conservative basis for initial load calculations.
All that being said, if this is an engineered system for ?specialty applications?, interpolating the values in Table 430.150 should meet your needs.
I suspect the motor(s) you are describing are either not for US domestic use or are for "specialty" applications.
Especially for low voltage applications, Art 430 "leans" very heavily toward NEMA "standard" motors. (Certain nameplate requirements in 430.7 definitely reflect NEMA and not foreign standards) While NEMA MG-1 recognizes both 50 & 60 Hz, it does not recognize non-standard voltages.
Table 430.150 is based on the highest FLA for any standard motor size that any NEMA manufacture makes. This permits general interchangeability of NEMA motors of the same HP and frame size without requiring the entire installation to be ?re-engineered.? It also provides a relatively conservative basis for initial load calculations.
All that being said, if this is an engineered system for ?specialty applications?, interpolating the values in Table 430.150 should meet your needs.
stew
Senior Member
- Location
- federal way,washington
Re: 300V Motor Full Load Current.
Just out of curiosity where have you found 300 volt motors? I have nevr heard of this voltage rating either on either 50 or 60 htz. What country is this in and where the heck do they get 300 volts?
Just out of curiosity where have you found 300 volt motors? I have nevr heard of this voltage rating either on either 50 or 60 htz. What country is this in and where the heck do they get 300 volts?
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: 300V Motor Full Load Current.
I have ran across some European equipment that had a 315 Volt rating at 50 Hz. 3phase, but not 300v? Maybe design for voltage drop? or like the 200 volt motors we run on 208?
[ August 03, 2004, 12:47 AM: Message edited by: hurk27 ]
I have ran across some European equipment that had a 315 Volt rating at 50 Hz. 3phase, but not 300v? Maybe design for voltage drop? or like the 200 volt motors we run on 208?
[ August 03, 2004, 12:47 AM: Message edited by: hurk27 ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: 300V Motor Full Load Current.
I would just do the formula:
I=hp x 746 / E x Eff x PF
I = current in Amperes
HP = horsepower
E = volts
Eff = efficiency
746 = watts per horsepower
PF = power factor
I would just do the formula:
I=hp x 746 / E x Eff x PF
I = current in Amperes
HP = horsepower
E = volts
Eff = efficiency
746 = watts per horsepower
PF = power factor
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Re: 300V Motor Full Load Current.
Since efficiency and power factor are unlikely to be known, if this isn't for US domestic use I'd simply use the nameplate amps. If they are known they will still calculate to the NP amps anyway.
If it is for domestic use I'd be inclined to use the FLC from the 460V column of Table 430.150 x 1.53. [Table Amps x 460/300]
There is already a precedent for interpolating based on Amps in 460.6(A)(1), but it is based on the standard voltages in the Table.
Since efficiency and power factor are unlikely to be known, if this isn't for US domestic use I'd simply use the nameplate amps. If they are known they will still calculate to the NP amps anyway.
If it is for domestic use I'd be inclined to use the FLC from the 460V column of Table 430.150 x 1.53. [Table Amps x 460/300]
There is already a precedent for interpolating based on Amps in 460.6(A)(1), but it is based on the standard voltages in the Table.
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