ANSI/IEEE vs. IEC Generator Temperature Ratings
ANSI/IEEE vs. IEC Generator Temperature Ratings
(OP)
On a combined cycle power plant proposal, a vendor provided steam turbine and gas turbine generator ratings versus ambient air temperature charts that had different curves for "IEEE Class B Rise, 0.85 pf" and "IEC Class B Rise, 0.85 pf". It looked like the ANSI/IEEE curve had about 30C difference in the allowable temperature rise at the same MVA. For example at 250 MW, 0.85 power factor, the IEEE curve is 0C ambient air, but the IEC curve shows 32C ambient air. The curves take into account the approach temperatures for the fin-fan air to water cooler and the water to hydrogen heat exchangers on the generator.
What is the reason for the 30C difference in the allowable temperature rise bewteen the IEEE C50.13 and the IEC standard (# unknown). Is it hot spot allowances, different test methods or different definitions?
What is the reason for the 30C difference in the allowable temperature rise bewteen the IEEE C50.13 and the IEC standard (# unknown). Is it hot spot allowances, different test methods or different definitions?





RE: ANSI/IEEE vs. IEC Generator Temperature Ratings
7.4.3 Temperature rise and temperature at base capability
For indirectly cooled windings, the temperature rises when operating at site shall be in
accordance with Tables 6, 7 and 8 of IEC 60034-1 as appropriate, adjusted as follows:
a) for primary coolant temperatures from 10 °C to 60 °C: add (40 – primary coolant temperature) K;
b) for primary coolant temperatures below 10 °C but not below –20 °C: add 30 K + 0,5 (10 – primary coolant temperature) K;
c) for primary coolant temperatures above 60 °C or below –20 °C, an agreement shall be reached;
For windings directly cooled by air or hydrogen the total temperatures when operating on site shall be in accordance with the limits of Table 12 of IEC 60034-1, adjusted as follows:
d) for primary coolant temperatures from 10 °C to 60 °C: no adjustment;
e) for primary coolant temperatures below 10 °C but not below –20°C: subtract 0,3 (10 – primary coolant temperature) K;
f) for primary coolant temperatures above 60°C or below –20°C, an agreement shall be reached.
RE: ANSI/IEEE vs. IEC Generator Temperature Ratings
I will have to have the generator vendor explain why the capability curve is so different between ANSI and IEC for the same operating conditions.
RE: ANSI/IEEE vs. IEC Generator Temperature Ratings
The electrical and mechanical designs were identical, just the speed change and different temperature rises etc defined in the specifications changed the rating criteria.
At the time, we offered 50Hz ratings to BS, IEC and other country specifications. For 60Hz applications we offered to ANSI.
This was because showing ratings for IEC and ANSI at the same frequency on the same piece of paper would potentially cause too many questions.........
RE: ANSI/IEEE vs. IEC Generator Temperature Ratings
Maybe I can get the client to relocate the power plant to Europe where generators apparently run cooler?
RE: ANSI/IEEE vs. IEC Generator Temperature Ratings
Please let us know what Siemens say