Inverter And Cyclo Converter Fed Drive

Jun 29 • Engineering Notes • 13 Views • No Comments

To know about invertor and cyclo converter fed drive,we will discuss invertor and cyclo inverter fed drive one by one.

INVERTER FED DRIVE:

At variable frequencies ac supply can be given to the induction motor for speed control using invertor source. At the input terminal the voltage source invertor has stiff dc voltage. Due to low internal impedence the terminal voltage of source invertor remains constant with load variation. Incase if there is any short circuit across its terminal then current rises very fast and this is because of low time constant of internal impedence ,such types of fault must be cleared by fast acting fuse links. Some of the configuration is shown below

DSC_0441

Voltage source invertor is like dc link convertor which is two stage conversion device. Smoothening is done with the help of inductance in dc links while dc voltage is maintained by capacitor.

CYCLO CONVERTER FED DRIVE:

A cyclo converter  is defined as a type of power controller which converts an ac voltage at supply frequency to ac voltage at load frequency without any intermediate dc stage. In the figure given below a three phase three pulse cyclo converter supplying to induction motor is shown.

DSC_0440

 

The voltage is controlled at rated flux condition within the converter. It work on the principle of line commutation. Forced commutation is not required  as it reduces complexity in the commutation circuit. The line power factor is poor at light load. It provides a sinosuidal wave form for voltages at all frequencies and the machine is free from torque pulsation with smooth operation and efficient system. The Harmonic losses are less. Cyclo converter is suitable for a low speed, large power and reversible drive.

FLUX VECTOR CONTROL:

The flux vector control the volts space core along with added additional blocks around the core for the improvement of performance of drive. The flux and torque producing currents are identified by current resolver which makes this value available to another blocks in the drive. Here the output of the current resolver is a frequency reference. Flux vector control and improves the dynamic response of the drive but in some cases it can control motor torque and with motor speed.

DSC_0000006

 

SENSORLESS OPERATIONS:

Sensor less vector operation is same as volt drive operation , it continues to operate as a frequency control drive along with slip compensation by keeping actual motor speed close to the desired speed. And the torque current estimator block determines the percent of current in the face along with the voltage providing torque current. By this estimation amount of slip and better speed control under load is determine.

DSC_0000007

IMPORTANT QUESTION:

1-Describe inverter fed drive?

Ans-At variable frequencies ac supply can be given to the induction motor for speed control using invertor source. At the input terminal the voltage source invertor has stiff dc voltage. Due to low internal impedence the terminal voltage of source invertor remains constant with load variation. Incase if there is any short circuit across its terminal then current rises very fast and this is because of low time constant of internal impedence ,such types of fault must be cleared by fast acting fuse links. Voltage source invertor is like dc link convertor which is two stage conversion device. Smoothening is done with the help of inductance in dc links while dc voltage is maintained by capacitor.

2-Describe cycloconverter fed drive?

Ans- A cycloconverter  is defined as a type of power controller which converts an ac voltage at supply frequency to ac voltage at load frequency without any intermediate dc stage. The voltage is controlled at rated flux condition within the converter. It work on the principle of line commutation. Forced commutation is not required  as it reduces complexity in the commutation circuit. The line power factor is poor at light load. It provides a sinosuidal wave form for voltages at all frequencies and the machine is free from torque pulsation with smooth operation and efficient system. The Harmonic losses are less. Cyclo converter is suitable for a low speed, large power and reversible drive.

3-Describe sensorless operation?

Ans- Sensor less vector operation is same as volt drive operation , it continues to operate as a frequency control drive along with slip compensation by keeping actual motor speed close to the desired speed. And the torque current estimator block determines the percent of current in the face along with the voltage providing torque current. By this estimation amount of slip and better speed control under load is determine.

4-Describe  flux vector control?

Ans- The flux vector control the volts space core along with added additional blocks around the core for the improvement of performance of drive. The flux and torque producing currents are identified by current resolver which makes this value available to another blocks in the drive. Here the output of the current resolver is a frequency reference. Flux vector control and improves the dynamic response of the drive but in some cases it can control motor torque and with motor speed.

GATE Syllabus-

1. Gate Syllabus for Electronics and Communication 2014

2. Gate Syllabus for Instrumentation Engineering 2014

3. Gate Syllabus for Engineering science 2014

IES Syllabus-

1.IES Syllabus for Electronics and Telecomm.

2. IES Syllabus for General ability

 

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