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#1 amirogerami

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Posted 29 August 2010 - 11:19 AM

In current business project I have to supply a motor and a liquid starter.
To achieve true understanding i need some information.
The motor descriptions are as below:
Rated power (kW): 1500
Rated torque (Nm): 9600.5
Rated voltage (V): 3300
Rated speed (rpm): 1492.00
Number of poles: 4
Rated frequency (Hz): 50.00
Rated current (A): 305
Moment of inertia (kgm2): 115.00
Rotor voltage (V): 1810
Rotor current (A): 498
According to supplier voltage & current needs of the Liquid starter are:
400 V 3AC 10 A
230V 1AC about 2A.
Dimensions are Approx. 1600 x 1400 x 2000.

I have read about how they work, but I need to know exactly what is happening.
Please correct me.
There are 3 electrodes in liquid starter that they come down. In top position resistance is Max and gradually by coming down resistance decrease. In this phase the current goes to rotor. The rotor begins to turn. When the R(min) is reached the starter short-circuits and the main power will flows to motor (stator).
I donít realize how the rotor V is 1810 when motor is 3300?
Is rotor begins to turn while the electrodes coming down?

I would really appreciate your comments.
Thanks

#2 Thomas1

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Posted 01 September 2010 - 06:42 PM

QUOTE (amirogerami @ Aug 29 2010, 06:19 AM) <{POST_SNAPBACK}>
In current business project I have to supply a motor and a liquid starter.
To achieve true understanding i need some information.
The motor descriptions are as below:
Rated power (kW): 1500
Rated torque (Nm): 9600.5
Rated voltage (V): 3300
Rated speed (rpm): 1492.00
Number of poles: 4
Rated frequency (Hz): 50.00
Rated current (A): 305
Moment of inertia (kgm2): 115.00
Rotor voltage (V): 1810
Rotor current (A): 498
According to supplier voltage & current needs of the Liquid starter are:
400 V 3AC 10 A
230V 1AC about 2A.
Dimensions are Approx. 1600 x 1400 x 2000.

I have read about how they work, but I need to know exactly what is happening.
Please correct me.
There are 3 electrodes in liquid starter that they come down. In top position resistance is Max and gradually by coming down resistance decrease. In this phase the current goes to rotor. The rotor begins to turn. When the R(min) is reached the starter short-circuits and the main power will flows to motor (stator).
I don't realize how the rotor V is 1810 when motor is 3300I?
Is rotor begins to turn while the electrodes coming down?

I would really appreciate your comments.
Thanks

QUOTE
I don`t realize how the rotor volts is 1810 when motor is 3300 ?

This is a wound rotor motor . The stator winding is seporate from the rotor. The voltage on the rotor is induced by the stator , the stator and rotor are not in series.

#3 jOmega

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Posted 09 September 2010 - 04:10 AM

QUOTE (amirogerami @ Aug 29 2010, 06:19 AM) <{POST_SNAPBACK}>
I donít realize how the rotor V is 1810 when motor is 3300?
Is rotor begins to turn while the electrodes coming down?



Wound Rotor Motors ...... are like a transformer ..

Consider the Stator to be the primary of the transformer ...

and the Rotor to be the secondary of the transformer

and the turns ratio Np/Ns is 1.8232 : 1


That should help to understand the difference in voltage.


The liquid starter is used to control the load resistance of the
Rotor Circuit which in turn, controls the torque and starting current of the motor in inverse proportion
to the resistance.

The greater the resistance in the rotor circuit, the lower the starting current and the higher the starting torque produced by the motor.

Perhaps the graphic below will further your understanding.



Kind regards,







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