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Starting Current |
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 Aug 14 2009, 06:09 AM
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Junior Member  Group: Members Posts: 2 Joined: 14-August 09 Member No.: 6,201  |
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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Aug 14 2009, 07:58 AM
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Posting Freak Group: Moderator Posts: 2,336 Joined: 24-April 02 From: Christchurch, New Zealand Member No.: 1 |
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. -------------------- Mark Empson administrator
Skype Contact = markempson | phone +64 274 363 067 LMPForum | LMP Tech Warehouse | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | LMP Software | Mark Empson Website |
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Aug 17 2009, 10:56 AM
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#3
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Junior Member Group: Members Posts: 2 Joined: 14-August 09 Member No.: 6,201 |
QUOTE (marke @ Aug 14 2009, 08:58 AM)  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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