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starting problem


dip04051978

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Hello Dear Friends,

 

I FOUND A PROBLEM OF STARTING OF SLIPRING MOTOR IN 1ST STEP OF OPERATION in our machine. THE DETAIL’S ARE US UNDER:

KW: 13.5

FLC : 29A

ROTOR V: 230

ROTOR A: 35

 

1ST STEP RESISTANCE : 6.84

2ND STEP RESISTANCE : 1.9

3RD STEP RESISTANCE : 0.76

4TH STEP RESISTANCE : 0.19

 

AT 1STEP MOTORS RUNS FOR A WHILE & STOPPED. CAN U HELP ME TO SOLVE THIS PROBLEM?? THE MOTOR IS USED FOR A TRAVEL ON A MOVING MACHINE. I THOUGHT THERE IS PROBLEM IN CAL. RESISTANCE.

 

My email id is dip04051978@yahoo.com.

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Hello dip04051978

 

The rotor resistance determines the slip at which maximum torque occurs. If the resistance is increased, then the slip at which the maximum torque occurs reduces.

 

From your description, I would expect that there is a problem with the thermal capacity of the 1st step resistors and that they are getting excessivly hot. This will probably cause the resistance to go high, and depending on where the torque curve lies in relation to the speed of traverse, the torque could drop and cause the stall to occur.

 

Remeber that there is a very high power dissipation in the resistors and that metalic resistors go high in resistance when hot, while liquid resistors tend to go low when hot.

 

Best regards,

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