From: Raybould, Keith Sent: Tuesday, December 01, 2009 3:17 PM To: Dawe, Craig; Heller, Ken; Massion, Gene; Mellinger, Ed; Etchemendy, Steve Subject: FW: MV converter efficiency Attachments: Mars MVC_16_06_2009.ppt Below is the info on P2A (deployed) MV converter efficiency from Alcatel. Currently Alcatel estimate efficiency of 80.8% from the data Craig/Ken measured in Sept (efficiency was 50% at the low loads back in July, but effic/load curve is too steep to be of any value) The measured efficiencies on test units at Alcatel in the lab at 2kW load were (a) 79% for 6kV input and (b) 73% for 8kV input; see slide #6 on their presentation attached). So P2A looks reasonable, Keith -----Original Message----- From: NICOL GEORGE [mailto:George.Nicol@alcatel-lucent.co.uk] Sent: Friday, October 30, 2009 5:50 AM To: EVANS TONY; Raybould, Keith Cc: COOK RICK; CORDIER ALAIN; DRYLAND Jon Subject: RE: MV converter efficiency Hello Keith, It may be worth adding that if sub converter failures occur, they would cause (relatively) small abrupt permanent increases in the MVC losses. At moderate loading levels, these should be of the order of tens of Watts each. This effect might be best seen by plotting a graph of successive measurements against time. Only readings taken at similar loadings should be compared, and you must be careful not to be misled by temperature effects, e.g. following load changes. Subject to the system having reached thermal equilibrium, I agree that your own early measurements would provide the best reference for future comparison. Regards George Nicol -----Original Message----- From: EVANS TONY Sent: 29 October 2009 15:15 To: 'Raybould, Keith' Cc: COOK RICK; NICOL GEORGE; CORDIER ALAIN; DRYLAND Jon Subject: RE: MV converter efficiency Hi Keith, Sorry for the delay in getting back to you. Using your results I have calculated an expected efficiency of 80.8 % as shown in the table below: input voltage 7.28 kV input current 0.48 A cable length 53.07 km line resistance 1 Ohms/km Calculated voltage at MVC I/P 7.255 kV Calculated I/P power 3.482 kW o/p voltage 372.7 V o/p current 7.55 A Calculated O/P power 2.814 kW Efficiency (%) 80.8 My only assumption is that the cable resistance is 1Ohms/km throughout, although this has only a very second order effect (calculating with cable resistance =1.4 Ohms/km changes efficiency by +0.1%). I think that the achieved efficiency of 80.8% is reasonable for this loading level. You should use this data as a reference for subsequent calulations of efficiency. If you need anymore advice do not hesistate to contact me. Regards Tony -----Original Message----- From: DRYLAND Jon Sent: 14 September 2009 10:21 To: Raybould, Keith Cc: EVANS TONY; NICOL GEORGE; CORDIER ALAIN Subject: RE: MV converter efficiency Hi Keith Thanks for the data. Tony and George are looking after this project now and will respond as soon as they can. Kind regards, Jon. -----Original Message----- From: Raybould, Keith [mailto:keith@mbari.org] Sent: 09 September 2009 23:14 To: DRYLAND Jon Subject: RE: MV converter efficiency Jon, Here are the V/I measurements we made with a higher load on the system. Does this give any better indication of the state of our P2A converter? The V and I on the shore that feeds into the marine cable are 7.28kV and 0.48A. Current then flows through 53km of OALC4 cable, 70m of OALC tail cable, Alcatel Cable Termination Assembly (CTA), the ODI HV connector into the MV converter housing. The output of the converter is 7.55 Amps at 372.7 Volts. Thanks Keith -----Original Message----- From: DRYLAND Jon [mailto:Jon.Dryland@alcatel-lucent.co.uk] Sent: Friday, July 24, 2009 12:56 AM To: Raybould, Keith Subject: RE: MV converter efficiency Hi Keith One of my colleagues is going to look into this next week - we'll try to answer ASAP Best regards, Jon -----Original Message----- From: Raybould, Keith [mailto:keith@mbari.org] Sent: 20 July 2009 23:53 To: DRYLAND Jon Cc: COOK RICK; EVANS TONY; CORDIER ALAIN Subject: RE: MV converter efficiency Hi Jon, The converter efficiency vs load plots have a very steep gradient at low power levels till they hit around 4kW, so the efficiency changes rapidly with small load changes down at the 1kW range. How does the converter efficiency vary with number of failed converter units? Are individual converter failures detectable at these low load levels? Thanks Keith -----Original Message----- From: DRYLAND Jon [mailto:Jon.Dryland@alcatel-lucent.co.uk] Sent: Thursday, July 16, 2009 8:34 AM To: Raybould, Keith Cc: COOK RICK; EVANS TONY; CORDIER ALAIN Subject: RE: MV converter efficiency Hi Keith I'm not sure if your OALC4 cable is 1.0 or 1.6 Ohm/km, but as you can see from the attached it doesn't make much difference. Your MVC is dissipating about 540W and operating with about 50% conversion efficiency. This sounds about right for these very lightly loaded conditions. Do you have any measurement data taken in your test tank (with similar load and input voltage)? This could be used for comparison to determine if the MVC has degraded since deployment. Additionally, it would be useful to know your planned load requirements for the near future - do you have some kind of "roadmap"? Kind regards, Jon. ________________________________ From: Raybould, Keith [mailto:keith@mbari.org] Sent: 14 July 2009 17:54 To: DRYLAND Jon; COOK RICK Subject: MV converter efficiency Jon, I promised to send power (V/I) measurements to you so that you could estimate the P2A converter efficiency to estimate whether any of the individual converters have failed. Below are those measurements. The V and I on the shore that feeds into the marine cable are 7.28kV and 0.15A. Current then flows through 53km of OALC4 cable, 70m of OALC tail cable, Alcatel Cable Termination Assembly (CTA), the ODI HV connector into the MV converter housing. The output of the converter is 1.47 Amps at 372.9 Volts. Hopefully you can estimate cable looses from shore power feed through the marine cable to the MV housing to estimate the converter efficiency, This should give us an idea of when we may need to plan to exchange the MV converters, Thanks Keith