Japan Increasingly its Submarine Propulsion (Diesels & Motors), Soryu TABLE

Submarine Propulsion in 7 lines. Air through snorkel is sucked into the Diesel Engine. Combustion from [spark and?] compressed diesel fuel produces the Diesel's mechanical power - Which then drives the Generator (which changes mechanical energy into electrical energy). The electricity and drives the Electric Motor which charges the Batteries. Diesels/Generator/Electric Motor/Magnets to rotate propeller to produce (about) 8-12? knot snorting speed. OR Batteries/Electric Motor/Magnets producing the silent running speed which is above 6 knots.
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Following Submarine Matters Possible Motor Modifications for Australia's Future Submarine, February 9, 2018 Anonymous kindly commented on February 5, 2018 (with a bit of further translation by Pete):

The Soryu Mk 2 (at 27SS in the Table below) importantly will have:

(A)  a modified propulsion motor (designated “SMC-8B”) [1]

(B)  accompanied by Lithium-ion Batteries (LIBs). LIBs provide various benefits such as a low 

       indiscretion ratio (IR) [a lower the ratio of time spent at periscope depth snorting to time   completely submerged 

(C)  flexibility of operation and high speed performance submerged and

(D)  12V25/25SB diesels used in the current Soryu Mk 1 Soryu Mk 2 prior to use of 12V25/31S in Soryu Mk 3.

The newly modified propulsion motor (designated “SMC-8B”) will benefit from the more powerful diesel and the more electrically powerful LIBs quick charging of LIBs in order to achieve flexibility of operation and high speed performance submerged. In Soryu Mk 1, low speed performance is emphasized because of low effective capacity of LABs. 

In the Soryu Mk 2, higher silent (6> knots) speed performance will be emphasized, because of drastically improved LIB and motor capacity. This allows higher silent speed fully submerged for a much longer period. 

In other words, the main objective of the SMC-8B is the improvement of maximum silent speed. Key factors will be optimized to reduce vibration/noise, in Anonymous's opinion. As result, maximum speed from point to point somewhat changes as shown in [2] and [3]. Even a tiny improvement in the existing 5 minute duration of the 20 knots maximum speed would require a much more powerful engine. Anonymous does not think such a tiny improvement has meaning in actual operation. [4]

[1]       Budget of Japanese Ministry of Defense (MoD)

Soryu Mk 1s have propulsion motor SMC-8 and Mk 2s have SMC-8B (where the B means first revision) see Table below. The degree of revision can be measured by the first year cost which is the cost of new equipment and so on in the first year.  In SMC-8B, the first year cost was budgeted suggesting that SMC-8B experienced huge modifications or SMC-8B is actually a new model. So overall the last Soryu Mk 1 (26SS with SMC-8) costs ¥51.7B FY2014 (see Table below). Then the cost for the first Soryu Mk 2 (27SS) jumps to ¥64.4B FY2015 of which the development and unit costs of the first SMC-8B are a part.

[2]       “FY2014 Annual Report on Life Cycle Cost Management”, Equipment

Procurement and Construction Office, Ministry of Defense (MoD), page 78, Tabale 2. The maximum submerged speed of 26SS (Soryu Mk 1 with Lead-acid Batteries (LABs) + AIP) and 27SS (Soryu Mk 2 with LIBs) are both 20 knots.

[3]       Using English wikipedia websites - LIBs have a greater average charge and discharge efficiency 80%-90% (see LIB sidebar) compared to LABs with a lower average in the 50%-95% (see LAB sidebar). A Soryu Mk 2 submarine using LIBs, like a Soryu Mk 1 submarine using LABs both will not exceed 20 knots.

[4]       Additional comments by Anonymous of February 13, 2018. Japanese submarines are not equipped with reduction gear. Their speeds are electrically adjusted. The DC motors of Oyashios and AC motors (PMSM) of Soryus have different adjustment systems. In the Soryu Mk 1 (SMC-8), maximum silent speed is greater than 6 knots. This may correspond to the maximum operating output of a small rotor. In the Soryu Mk 2 (SMC-8B) an increased maximum silent speed for a longer period is expected.

Since 20 knots for 5 minutes is a performance limitation of the SMC-8, achieving 20 knots for an hour would require major modifications such as an increased cooling system, bigger rotor and stator, reinforced bearing and shaft. The speed of a submarine is proportional to cubes of output of the propulsion motor. A 10% increase in maximum speed (from 20 knots to 22 knots ) would need a 33% increase in output (from 5.9MW to 8MW). This requires major modifications. These modification may cause additional vibration leading to greater submarine noise.

Achieving a higher silent speed for a longer time within the framework of the submarine's current output is a more realistic objective.

TABLE SORYU & Oyashio Program as at March 14, 2018 

SS No. Diesel Type Motor	Build No Name	Pennant No.	MoF approved amount ¥ Billions FY	LABs, LIBs, AIP	Laid Down	Laun -ched	Commi ssioned	Built By
5SS Oyashio 2 Toshiba motors	8105 Oyashio	SS-590/ TS3608	¥52.2B FY1993	LABs only	Jan 1994	Oct 1996	Mar 1998	KHI
6SS-15SS Oyashios  10 subs 2 Toshiba motors SMC-7?	8106 -8115 various	SS-591-600	¥52.2B per sub FY1994-FY2003	LABs only	15SS Feb 2004	15SS Nov 2006	15SS Mar 2008	MHI & KHI
16SS Soryu Mk 1 12V25/25SB SMC-8	8116 Sōryū	SS-501	¥60B FY2004	LABs + AIP	Mar 2005	Dec 2007	Mar 2009	MHI
17SS	8117 Unryū	SS-502	¥58.7B FY2005	LABs + AIP	Mar 2006	Oct 2008	Mar 2010	KHI
18SS	8118 Hakuryū	SS-503	¥56.2 FY2006	LABs + AIP	Feb 2007	Oct 2009	Mar 2011	MHI
19SS	8119 Kenryū	SS-504	¥53B FY2007	LABs + AIP	Mar 2008	Nov 2010	Mar 2012	KHI
20SS	8120 Zuiryū	SS-505	¥51B FY2008	LABs + AIP	Mar 2009	Oct 2011	Mar 2013	MHI
No 21SS			No 21SS built
22SS	8121 Kokuryū	SS-506	¥52.8B FY2010	LABs + AIP	Jan 2011	Oct 2013	Mar 2015	KHI
23SS	8122 Jinryu	SS-507	¥54.6B FY2011	LABs + AIP	Feb 2012	Oct 2014	7 Mar 2016	MHI
24SS	8123 Sekiryū	SS-508	¥54.7B FY2012	LABs + AIP	15 Mar 2013	2 Nov 2015	13 Mar 2017	KHI
25SS	8124 Seiryū	SS-509	¥53.1B FY2013	LABs + AIP	22 Oct 2013	12 Oct   2016	12 Mar 2018	MHI
26SS end of SMC-8s	8125 Shoryū	SS-510	¥51.7B FY2014	LABs + AIP	2014	6 Nov 2017	Mar 2019?	KHI
27SS First Soryu Mk 2 12V25/25SB first SMC-8B	8126	SS-511	¥64.4B FY2015	LIBs only	2015	2018?	Mar 2020	MHI
28SS  Second Soryu Mark 2 12V25/25SB SMC-8B	8127	SS-512	¥63.6B FY2016	LIBs only	2016?	2018?	Mar 2021?	KHI
29SS First Soryu Mk 3 12V25/31S SMC-9?	8128	?	¥76B FY2017	LIBs only	?	?	2023?	MHI?
30SS Second Soryu Mk 3 12V25/31S	8029?	?	¥71.5B FY2018	LIBs only	?	?	2024?	KHI?

Table from information exclusively provided to Submarine Matters. LABs = lead-acid batteries, AIP = air independent propulsion, LIBs = lithium-ion batteries. ¥***B = Billion Yen. MHI = Mitsubishi Heavy Industries, KHI = Kawasaki Shipbuilding Corporation of Kawasaki Heavy Industries. On Feb 13 2018 Diesel and Motor types were added.

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Anonymous and Pete