How to start highinertia load, with DOL method, without taking more current.

 

I am not really sure about your setup, but if you are using a variable speed AC drive to run this motor, you can add intertia compensation blocks in your drive software to control this high inertia load better.

 

Thank you for suggestion. But, Unfortunately,
When you stop the supply..the regenerative power will destroy your AC DRIVE CAPACITORS...

>I am not really sure about your setup, but if you are using a variable speed AC drive to run this motor, you can add intertia compensation blocks in your drive software to control this high inertia load better.<

 

Hi
You can use AC drives that have regenration facility. So when the drive decelerates the energy is feedback to the system. This gives better control and energy saving as well.

The other possibility is to go for softstarters

bye
Veerendran

 

If DOL is the ONLY uption you have you can use centrigugal clutch in between motor and the load.
This method is widely used in ball mills or similar heavy starting loads.

Best regards,
Sekar

 

Responding to Prasanna's Fri, Sep 20, 10:28 am, query:

DOL, or Direct-On-Line starting, will not enhance a motor's design starting characteristics, unless a higher than nominal voltage is applied.

The fact that the load is high-inertia does not influence break-away torque. Nor does it impact on the net accelerating torque, i.e., load minus motor. However, load inertia significantly affects starting or run-up time.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Look carefully at the torque curve for the motor and the voltage dip caused by the large start currents.I have helped trouble shoot a (2 pole)motor that would stall on start because of lack of torque. The "published" torque cruve was sufficient but because of voltage drop at start the torque curve was diminished.

It may be worth looking at using an autotransformer to boost the voltage on start.

 

> How to start high-inertia load, with DOL method, without taking more current. <

We have successfully started a 150 hp 1800 rpm induced draft fan motor which took over 2 min. to accelerate to full speed. This is a full voltage start (across the line start). We added a contactor and timer to short accross the overload heaters to test running current not the first 2 min. of starting current. The motor can only start 4 times per day and start no more than once per 15 min. Delta connected motors are much more forgiving in these types of applications.

 

Responding to Wm Hinton's (Wed, Oct 9, 1:03pm) comment:

I strongly disagree with you about delta-wound motors being more forgiving in this situaton. From a qualitative viewpoint, starting time is excessive.

If you want a quantitative viewpoint, please furnish particulars, especially position of the damper or vane during startup.

Regards,
Phil Corso, PE
(Boca Raton, FL)