International Conference Power Plants 2014-Zlatibor 29-31.10.2014 Society of Thermal Engineers of Serbia ELECTRO THERMAL TESTING OF HIGH VOLTAGE HIGH FREQUENCY ESP POWER AR70/1000 Slobodan N. Vukosavić*, Željko V. Despotović**, Nikola Popov*, Nikola Lepojević* School of Electrical Engineering, University of Belgrade*, boban@etf.rs Institute “Mihajlo Pupin”, University of Belgrade**, zeljko.despotovic@pupin.rs

INTRODUCTION The modern power supplies of electrostatic precipitators (ESP) are based on high voltage high frequency (HVHF) power converters. Developed HVFF ESP power, under commercial name AR70 / 1000, (70kV, 1000mA) is based on a distributed multi-resonant topology. This power it had to be subjected to a series of pure electrical tests (short circuit test, open circuit test, full load test), but also of thermal characterization and electro thermal testing, before delivery and exploitation in real conditions on the thermal power plant (TPP) blocks. This paper describes a methodology of electrical thermal testing of the proposed ESP power, as well as experimental results obtained during tests and thermal heating in laboratory conditions at nominal output voltage 70kVdc and the nominal output current 1000mA, i.e. power of 70kW. The performed experimental results and procedure showed acceptable values ​​and limitations, which was carried out the ​​verification of ESP power prior to delivery and installation on the real exploitation conditions on TPP blocks.

“HEAT SOURCES” IN ESP POWER AR70/1000 Basic electrical scheme HVHF distributed multi resonant topology AR70/1000 for ESP power There are three main thermal parts (heat sources) of ESP power AR 70/1000: cubicle of HF IGBT power converter, oil tank with corresponding equipment HV insulator in which is connect ESP load

ELECTRO-THERMAL INSTALLATION FOR TESTING ESP POWER AR70/1000

ELECTRICAL INSTALLATION of ESP POWER AR70/1000 Single pole electrical scheme of test installation (b) three-dimensional view of AR70/1000 power with the positions of associated equipment’s

DISTRIBUTION OF POWER LOSSES in ESP POWER AR70/1000 - dissipation losses at the input of three-phase rectifier - dissipation in DC link circuit - dissipation losses in IGBT H-bridge ( part P’γ3 dissipated in outdoor of cubicle and part P”γ3 dissipated in oil tank - dissipation losses on the HVHF transformer and HV rectifier

THERMAL CHARACTERIZATION OF ESP POWER AR70/1000 (i)-measuring points in HVHF transformer oil tank (ii)-measuring points at HVHF transformer (windings, magnetic circuit and oil temperature) (iii)-measuring points in HF converter DS2000 (H-bridge, input 3ph- rectifier, DSP controller) Disposition of measuring points of characteristic temperatures in ESP power AR70/1000, view on the right lateral side, (b) view on the top side (c) view on the front side

(ii) TEMPERATURE IN HVHF TRANSFORMER ( end measured values) CHARCTERISTIC MAEASURING POINTS (thermal characterization of ESP power AR70/1000) (i)-measuring points in HVHF transformer oil tank (ii)-measuring points at HVHF transformer (windings, magnetic circuit and oil temperature) (iii)-measuring points in HF converter DS2000 (H-bridge, input 3ph- rectifier, DSP controller) (i) OIL TANK (T1….T14) (ii) TEMPERATURE IN HVHF TRANSFORMER ( end measured values) T1 Heat sink DS2000 ΘCu1 Primary side winding (Cu1) T2 Oil temperature in tank ΘCu2 Secondary side winding (Cu2) T3-T8 Heat sink ribs (lateral side 0%-20%-40%-60%-80%-100%) ΘFe Magnetic circuit (ferrite-Fe) T9 Air temperature (fans of DS2000) Θtransf.oil Temperature of transformer oil T10 Top side of oil tank (iii) MEASURED TEMPERATURE IN DS2000 (end measured values) T11 Indoor of cubicle-position 1 Θ12 V-bus bar (AT+) *see Fig.1 T12 Indoor of cubicle-position 2 Θ45 Block capacitor in DS2000, 0.47uF/850V, MKP-CS13 ( <70ºC) T13 Temperature of electrolytic capacitors in DC link circuit Θ78 Hexagonal pad bollard , U bus bar (AT+) T14 Ambient temperature Θ10-11 Temperature of electrolytic capacitor in DC link circuit

EXPERIMENTAL RESULTS-Test No1 Thermal characterization of ESP power AR70/1000 at switching frequency f=6.9 kHz, and output power 61.35kW; power losses = 4kW

output power 57.25kW; power losses = 3kW EXPERIMENTAL RESULTS-Test No2 Thermal characterization of ESP power AR70/1000 at switching frequency f=6.4kHz, and output power 57.25kW; power losses = 3kW

EXPERIMENTAL RESULTS-Test No3 Thermal characterization of ESP power AR70/1000 at switching frequency f=7.4 kHz, and output power 67.45kW; power losses = 3.65kW

output power 65.6kW; power losses =3.67kW EXPERIMENTAL RESULTS-Test No4 ambient temperature was below 5°C, compared to the previous Test No3 Thermal characterization of ESP power AR70/1000 at switching frequency f=7.4 kHz, and output power 65.6kW; power losses =3.67kW

EXPERIMENTAL RESULTS-Test No5 Thermal characterization of ESP power AR70/1000 at switching frequency f=7.4 kHz, and output power 68.08kW; power losses = 3.8kW, air flow speed (side fans) 2.1 m/s

EXPERIMENTAL RESULTS-Test No6 Thermal characterization of ESP power AR70/1000 at switching frequency f=7.4 kHz, and output power 68.18kW; power losses =4.5kW,air flow speed (side fans) 3.5 m/s

EXPERIMENTAL RESULTS-Test No7 The best effect is achieved at the air flow velocity of 5.2m/s, in which case the oil temperature is reduced to the value less than 40°C !!!!!! Thermal characterization of ESP power AR70/1000 at switching frequency f=7.4 kHz, and output power 68.10kW; power losses =4.5kW, air flow speed (side fans) 5.2 m/s

FORCED COOLING of OIL TANK of AR70/1000 OUT air flow IN air flow A more modest effect of forced cooling was applied on decrease the temperature of the electrolytes in DC link circuit, or on the temperature T13. In the case of forced cooling with a velocity from 2.1m/s temperature T13 was still above the threshold value from 70°C. At velocity from 3.5m/s the temperature was also above the threshold of 70°C. At the flow velocity from 5.2m/s, this temperature was reduced at the value of about 69ºC.

FORCED COOLING of HVHF CUBICLE OUT AIR FLOW HVHF unit IN AIR FLOW FAN CUBICLE of AR70/1000 For this reason, it is performed additionally forced cooling of HVHF cubicle of AR70/1000 power, with fan, which is placed on the lower right side of the cubicle, as shown in figure (in/out air flow). Applying this cooling system the temperature of DC electrolytes was significantly reduced (on values approximately 40-50ºC).

DISPOSITION AR70/1000 and INSTALLATION in real exploitation conditions ACAD DRAWING Cubicle of AR70/1000 AR70/1000 HV rectifier TPP environment

CONCLUSIONS In this presentation is described thermal characterization of ESP power AR70 / 1000. In addition to the many standard electrical tests was performed detailed thermal testing of this power. These tests have been mandatory before delivery and after that, installing these devices on ESP station, on TPP. Thermal tests showed some disadvantages of the natural cooling initially anticipated. Applying forced cooling of the transformer oil tank and cubicle of HF resonant IGBT converter, are solved all these problems and achieved the acceptable values ​​increase in temperature in relation to ambient temperature under all operating regimes and in steady state. After this ESP power AR70/1000, were ready for final delivery.

ACKNOWLEDGEMENTS The proposed multi-resonant topology represents the basis of power supply AR70/1000 developed in the framework of scientific cooperation between the School of Electrical Engineering, the University of Belgrade and Mihailo Pupin Institute, University of Belgrade. This investigation has been carried out with the financial support of the Serbian Ministry of Science- Project No: TR33022-“Integrated system for flue gas cleansing and development of technologies for zero pollution power plants” and Public Enterprises EPS Serbia.

THANK YOU IN ATTENTION!!!! OCTOBER 2014 PRESENTER: Željko V. Despotović, PhD.E.E Senior Research Associate Mihajlo Pupin Institute, Belgrade SERBIA