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Home » Motor protection » MV motor started by soft start device
MV motor started by soft start device
What need to be concerned for MV motor installed in Hazardous Area (classified according to NEC 500) and to be started by soft start device? Is there any specific electrical data/information that needs to be given to motor vendor apart from the Plant Electrical system?
It's about a MV motor. What type of soft start do you have in mind? Different methods present different requirements. Do you require a really gentle start, with full control of the developed torque and acceleration during the whole of the start, or can you accept some step-wise starting?
Are you thinking of soft starting just to protect other areas of your supply network from voltage variations?
Are the motor windings designed to withstand the potential voltage spikes associated with thyristors turning off/on in neighbouring phase windings?
Is the motor cooling fans and rotor designed to provide adequate cooling during running for prolonged periods at reduced speed during start?
Are there any critical frequencies that you must avoid during start, to avoid any resonance problems?
You should consider all these and other issues, preferably even before you order the motor.
The motor will start as softer as lower the initial voltage is. However, the lower the initial voltage is, the lower the starting torque is. Therefore, you have to check against your driven load torque curve how low starting torque you can allow.
From the other hand, the motor has to be designed to enable starting at significantly low voltage (70%-like), what relates to the rotor design, especially to the rotor cage rods form and positioning. Therefore, you have to provide the motor manufacturer with all relevant information. Otherwise, incompatible motor will become a very expensive-but-useless piece of copper and iron because it won't be able start under the conditions on site.
It's about a MV motor. What type of soft start do you have in mind? Different methods present different requirements. Do you require a really gentle start, with full control of the developed torque and acceleration during the whole of the start, or can you accept some step-wise starting?
Are you thinking of soft starting just to protect other areas of your supply network from voltage variations?
Are the motor windings designed to withstand the potential voltage spikes associated with thyristors turning off/on in neighbouring phase windings?
Is the motor cooling fans and rotor designed to provide adequate cooling during running for prolonged periods at reduced speed during start?
Are there any critical frequencies that you must avoid during start, to avoid any resonance problems?
You should consider all these and other issues, preferably even before you order the motor.
The motor will start as softer as lower the initial voltage is. However, the lower the initial voltage is, the lower the starting torque is. Therefore, you have to check against your driven load torque curve how low starting torque you can allow.
From the other hand, the motor has to be designed to enable starting at significantly low voltage (70%-like), what relates to the rotor design, especially to the rotor cage rods form and positioning. Therefore, you have to provide the motor manufacturer with all relevant information. Otherwise, incompatible motor will become a very expensive-but-useless piece of copper and iron because it won't be able start under the conditions on site.