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Starting Current


Subramanian

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We would like to have a 600KW 415V centrifugal air Comressor.As this has to run on Gas Generator supply,what is the type of starter that can be used.

We would like to have a min Starting current.As centrifugal Compressor has to operate on fixed speed, speed variation is not required.

We would like to know who can supplysuitable starter.What will be the min Starting current possible.

 

Thanks

AGS

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Hello Subramanian

 

Welcome to the forum.

 

The minimum start current is a function of the minimum load torque required (determined by the compressor) and the motor design.

The first step is to obtain the compressor speed torque curve during start to determine the required start torque.

The second step is to obtain the motor curves for torque against speed and current against speed at full voltage.

 

As you reduce the start voltage, the current reduces by the same ratio and the torque reduces by the square of the current reduction.

With this knowledge, you can plot a series of start torque curves for different start voltages or different start currents and can then determine the lowest current that can start the compressor.

A good soft starter is an economic way of regulating the start current.

If you need to further reduce the start current, you can consider the motor selection and look for a rotor design that has more resistance and produces a higher torque at a lower start current. (There are big differences between motor designs.)

Alternatively, look at a wound rotor motor and a slip ring starter, or a VFD.

 

Have a look at http://www.lmphotonics.com/m_control.htm and http://www.lmphotonics.com/m_start.htm

 

Best regards,

Mark.

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Hello Subramanian

 

Welcome to the forum.

 

The minimum start current is a function of the minimum load torque required (determined by the compressor) and the motor design.

The first step is to obtain the compressor speed torque curve during start to determine the required start torque.

The second step is to obtain the motor curves for torque against speed and current against speed at full voltage.

 

As you reduce the start voltage, the current reduces by the same ratio and the torque reduces by the square of the current reduction.

With this knowledge, you can plot a series of start torque curves for different start voltages or different start currents and can then determine the lowest current that can start the compressor.

A good soft starter is an economic way of regulating the start current.

If you need to further reduce the start current, you can consider the motor selection and look for a rotor design that has more resistance and produces a higher torque at a lower start current. (There are big differences between motor designs.)

Alternatively, look at a wound rotor motor and a slip ring starter, or a VFD.

 

Have a look at http://www.lmphotonics.com/m_control.htm and http://www.lmphotonics.com/m_start.htm

 

Best regards,

Mark.

 

 

 

 

Hello Mr.Mark

 

Thanks for your prompt guidance.

 

 

 

Best Regards

 

Subramanian

 

 

 

 

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