It has been 15 years since after the exhaust turbocharging system being applied to two cycle marine Diesel engine.
To cope with the demand for recent trend of remarkable larger size and greater output of engines, extensive study for advancement of turbocharger efficiency and its suitability to main engine resulted turning out of highly turbocharged engine of over 100% of turbocharging degree.
At the beginning stage of exhaust turbocharging system, generally“Impulse system”have been adopted. However, from a few years before a large number of“Constant pressure system”has been introduced.
So far M. A. N. KZ type Diesel engine is concerned, comparatively at an early stage, constant pressure system has been applied.
With regard comparable merits and demerits of both systems have long been discussed, but it can not be denied the fact that it becomes larger size and greater output of engines, it would eventuate to apply constant pressure system and prospects of strong demands of constant pressure system will be increased hereafter which proves the superiority of constant pressure system over the impulse system.
But as one of the weak points of constant pressure system is that it does not match with main engine at low load, especially in KZ engine which provides the piston underside pump and besides in case of parallel operation with turbocharger be carried out, it is necessary to install a special scavenging air control system in order to prevent turbocharger going in to the surging range at low load.
For the purpose of solving of this problem, many devices have been studied, proposed and put in practical use.
In this paper, we will introduce to several scavenging air control system intending to improve of performances at low load under the condition of constant pressure system and further we will state about an experiment and analysis studied by us of constant pressure parallel with injector system which comprehensively adopted recently to KAWASAKI-M. A. N. KZ engines.

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The motor generators, resistors and inverter-rectifier systems have been used as the electric control device supplied from a DC power source. But, since the thyristor chopper was developed, it's high performance has been expected in many applications such as a speed control device of a DC motor.
The thyristor chopper switches on and off the DC power delivered to the load at high rate, to control it by changing the ratio of the on and off time. And many circuit configurations have been presented for paticular uses. However, a thyristor chopper circuit which is employed an auxiliaiy thyristor in it's commutation circuit seems to be best suited for general applications. The paper presents an analysis and some characteristics of this type of the thyristor chopper circuit.
One cycle of the operation of the thyristor chopper can be divided into six intervals according to the circuit state and the analysis is executed for each interval. The results show that the output voltage of the thyristor chopper with an auxiliary thyristor for commutation consists of three parts: (1) the voltage directly controled by the trigger circuit, (2) the voltage drop due to the circuit elements, (3) the voltage which is affected by the commutation circuit operation. The last part is nearly in inverse proportion to the load current, so that the output voltage of the chopper circuit slightly decreases as the load current increases.
The characteristics of an experimental circuit confirms the results of this analysis.

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