Voltage deviation

[Lmp]

How are voltage deviations typically handled for industrial loads on long radial taps? For example, I have a load being served from a long utility feed that is a 46/ 12.47 and then stepped down again to 480v. The voltages seen on my 480 system swing from 460v to 500v. A lot of my equipment is tripping off at the 460-450v range. During off peak times the voltage may be as high as 500-510v. How do you handle the low voltage and also the wide voltage spread?

 

[LEO2854]

How are voltage deviations typically handled for industrial loads on long radial taps? For example, I have a load being served from a long utility feed that is a 46/ 12.47 and then stepped down again to 480v. The voltages seen on my 480 system swing from 460v to 500v. A lot of my equipment is tripping off at the 460-450v range. During off peak times the voltage may be as high as 500-510v. How do you handle the low voltage and also the wide voltage spread?

Welcome to the forum.:thumbsup:

This sounds like a transformer issue.

 

[Julius Right]

If this it is the measured voltage at induction motors terminal while in running process then-I think-there are the legal limits.
NEMA MG1 Standard ch.12.44.1 for small and medium voltage and 20.14.1 for large motors states the limits for voltage deviation at rated frequency as +/ 10%.
IEC 60067-1 ch.7.3 "Voltage and frequency variations during operation" states:
Zone A +/-5% at rated frequency ; Zone B +/-10% at rated frequency
A machine shall be capable of performing its primary function, as specified in Table 3[rated torque],continuously within zone A.
A machine shall be capable of performing its primary function within zone B but may exhibit greater deviations from its performance at rated voltage and frequency than in zone A.:happyyes:

 

[broadgage]

Does not sound too bad to me.
If the permitted tolerance is plus or minus 5%, then what you are getting is close to that.

105% of 480 volts is 504 volts.
95% of 480 volts is 456 volts.

Most utilisation equipment should accept from 00% up to 110% of the nominal voltage.

If the voltage at the service is outside of permitted tolerances, then that is probably a utility problem, they may need to provide a larger transformer and/or thicker wires, or perhaps bring a higher voltage nearer the customer.

Voltage regulating equipment is readily available but normally only applied to especialy sensitive loads, not to heavy machinery.

 

[Jraef]

A lot of my equipment is tripping off at the 460-450v range.

Actually, what is "tripping off"? Sounds to me as though someone installed voltage monitoring devices and set the tolerances too low. I see this a lot with OEMs from other countries who do not understand the nature of power systems here in the US. They read that the motor nameplate says "460VAC" so they set the trip threshold at 460V. That is a serious nuisance problem, as you have already experienced. I would look for the device that is 'tripping off" and check the settings. You want to allow for that +-10% of 460V that the equipment SHOULD be rated for.

The one issue to be aware of though is that if the equipment did come from overseas, a sneaky little trick that OEMs sometimes use on 460V rated equipment is that they use IEC designed motors that are rated for 380V 50Hz, knowing that if you apply 460V 60Hz, the ratio of voltage and frequency is the same so the motor produces the same rated torque without overheating, albeit at a 20% higher speed. The secondary problem however is that IEC motors do not necessarily have the same design voltage tolerances that we have in NEMA motor design specs. So they may have PURPOSELY set the voltage trip threshold low BECAUSE they know that, which makes it YOUR problem now.