On-board Variable Frequency Soft Starters for Marine

The ships will experience a starting process of main propulsion motor from static condition or free rotation condition when they are started from berthing or running status, if it is started directly with the supply network of the ship, as the breakaway starting current of the electrical machinery is very large, it usually exceeds the capacity of the supply network on the ships. To make the ships smoothly started without affecting the normal power supply of the whole marine electric power system, the main propulsion motor of this kind of ships should be equipped with soft starting devices. In addition, when the ships are sailing in the harbor district, they usually need to run at a low speed, thus the main propulsion motor also needs to operate under the frequency conversion with a low speed. The marine variable frequency soft starters researched, developed and produced by our company consists of a single electronic control panel, which can realize the frequency conversion soft starting and frequency conversion low-speed running of the main propulsion motor of ships, there are 3 kinds of work patterns, “on the spot”, “beside the machine” and “remote control”, the starting torque of this frequency conversion soft starter is high, the starting is fats, torque is steady and fluctuation is small, so it is the ideal choice of soft starting and low-speed frequency conversion running of main propulsion motor of ships.

The CTR-SVFD-1250/690 marine variable frequency soft starters of CenteRole (Dalian) Electric Transmission Technology Co., Ltd. consists of a single electronic control panel, the material of panel is good, the surface of panel body is protected by static spraying, the mode of feed-in and feed-out cables is down-in and down-out, there is an electric heater installed in the panel, which can prevent moisture condensation.

The main circuit consists of 2 parts, the diode rectifier module and the IGBT 3-phase inverter. The 3-phase bridge rectifier constituent by the diode modules commutate the 690V 3-phase alternating voltage into direct voltage, and the IGBT 3-phase inverter changes the direct voltage into the alternating voltage whose fundamental frequency and amplitude can both be adjusted to export it to the main propulsion motor.

Through properly control the voltage and frequency functioned on the stator winding of electromotor, with the guarantee that the current of electromotor will not exceed the highest output current limitation of this device, gradually increase the rotate speed of the electromotor until it reaches the rated speed of the electromotor. During this period, as the electromotor is under the frequency conversion functioning condition, the load is at the 0 screw pitch, then the current of electromotor and the current supplied by the power grid is both small.

After the rotation speed of the electromotor reaches the rated value, the control machine in the panel will automatically lock the phase position of the output voltage and the power supply, the PLC in the panel will rapidly break the output contactor, and rapidly close the bypass breaker before the remanence of electromotor obviously decreases, then it is can smoothly realize the grid-connected operation of electromotor.

After this, the electric supply of electromotor will be provided by the power grid of the ship and enter the continual running status, and the soft starting process of electromotor is over.

Environmental conditions

Main technical specifications

 “Cohesion wheel” 28000 ton working ship of Wuchang Shipbuilding Industry Group Co., Ltd. 2000kW main propulsion marine frequency conversion and electrical machinery soft starter   2 sets

“Cohesion wheel” 28000 ton working ship of Wuchang Shipbuilding Industry Group Co., Ltd.  1000kW bow thruster marine frequency conversion and electrical machinery soft starter   1 set