Reducing starting current of motor

Thread Starter

arcteryx

Joined Feb 14, 2011
8
Is there any way to reduce the starting current of a motor since it will cause trip/blackout during start? The start configuration for the motor is direct-on-line (DOL).Need suggestion.Thanks!
 

crutschow

Joined Mar 14, 2008
24,989
You can momentarily switch in a power resistor or inductor in series with the motor to limit the starting current and then switch it out (short across it) when the motor has finished its start.
 

t_n_k

Joined Mar 6, 2009
5,455
If this is a typical 3-phase AC induction motor with stator windings configurable in Star or Delta then a useful technique is the star/start-delta/run method. This requires some control hardware - as will any soft starting method.
 

GetDeviceInfo

Joined Jun 7, 2009
1,724
Is there any way to reduce the starting current of a motor since it will cause trip/blackout during start? The start configuration for the motor is direct-on-line (DOL).Need suggestion.Thanks!
what's tripping, your overcurrent or overload? Does the load require a softstart scheme? Are you hooked into inadequate supply?
 

Thread Starter

arcteryx

Joined Feb 14, 2011
8
I just got the datasheet from the supplier. The starting current of the motor is high. 390A. The start configuration of the motor is DOL. So, is there any way that I can reduce it? By the way, is there any effect to the motor if the starting current is high?
 

jimkeith

Joined Oct 26, 2011
540
Check out this soft start control--they are available for even higher currents, but this seems to be the largest handled by Grainger--the line current passes through antiparallel SCRs that are phased on gradually to reduce starting surge--75A is the full load current--during starting, the current will be roughly 150A. To reduce conduction losses, some units have a contactor that bypasses the SCRs after starting.

http://www.grainger.com/Grainger/SCHNEIDER-ELECTRIC-Soft-Start-6VMA0?Pid=search
 

THE_RB

Joined Feb 11, 2008
5,438
I just got the datasheet from the supplier. The starting current of the motor is high. 390A. The start configuration of the motor is DOL. So, is there any way that I can reduce it? By the way, is there any effect to the motor if the starting current is high?
I don't want to sound like a grumpy old guy but a 390amp motor is an expensive professional device and the way it is started, wired, safely fused and run should all have been handled by a properly trained professional.
 

sonda

Joined Oct 30, 2012
10
You can momentarily switch in a power resistor or inductor in series with the motor to limit the starting current and then switch it out (short across it) when the motor has finished its start.
can you please explain this bit more, if possible. thanks..
 

spinnaker

Joined Oct 29, 2009
7,835
can you please explain this bit more, if possible. thanks..
If you don't understand that then you should not be messing with this motor and those currents.

See RB's post. You could easily kill yourself or someone else. Even a whole group of people or cost you company millions of US dollars in a burned down building and / or lost business.

Get someone that knows exactly what they are doing to install this motor for you. A motor of that size must cost a lot of money. It is not going to cost much more to have it installed properly.

While we have some extremely talented and helpful people on this forum. a hobby forum is no place to seek advice of this type. No one is on location to see the exact situation.

We have a saying "Penny wise and pound foolish".

It means you are trying to save a small amount of money while risking a great deal of money.
 

sonda

Joined Oct 30, 2012
10
If you don't understand that then you should not be messing with this motor and those currents.

See RB's post. You could easily kill yourself or someone else. Even a whole group of people or cost you company millions of US dollars in a burned down building and / or lost business.

Get someone that knows exactly what they are doing to install this motor for you. A motor of that size must cost a lot of money. It is not going to cost much more to have it installed properly.

While we have some extremely talented and helpful people on this forum. a hobby forum is no place to seek advice of this type. No one is on location to see the exact situation.

We have a saying "Penny wise and pound foolish".

It means you are trying to save a small amount of money while risking a great deal of money.
thanks for your advice mate. i m not trying to burn down a place or people... i just ask this because i thought its interesting to know. thanks anyway.
 

BillB3857

Joined Feb 28, 2009
2,533
Also, remember that reduced current=reduced torque. What kind of load is on the motor? Does it require full starting torque of the motor?
 
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