ESP Softstart

We use this step up transformer for ESP applications by using VSD with very high efficiency .

Plus soft start doesn't change frequency applied it only change the voltage

Thnx,

Oops. I misread that, as JRaef noted. Marked OT.

I think you'll find it's down to the harmonics created by the soft start unit.

No wonder the transformer isn't happy and complains.

On a soft starter, it only controls RMS voltage via phase angle control, not frequency. It should work fine for boosting voltage to the motor, this is done all of the time in the ESP industry. So this is really about the fact that you do not fully understand soft starters.

Soft starters do not do anything at all unless there is a load for them to fire into, they need the current flow in order to make the SCRs function. If you were to have a LV motor and no transformer, but the motor was not connected yet, the soft starter would simply fault out on the fact that there is no current flow. But now you have added a transformer, and the transformer has magnetizing current flow. So the soft starter "thinks" this is the load, it operates, but the impedance doesn't change after the first cycle or two, so it just keeps pumping current into it at its current limit level until something shuts it down, in this case you.

If you want to test it before connecting it to the ESP, find and connect any 3 phase motor, the size is somewhat irrelevant. The only possible issue is that you will not likely see any ramping on a small unloaded motor. It's taking place, but probably so quickly that you cannot perceive it. Most modern soft starters have what is called an "anti-oscillation circuit" that detects when a motor is t full speed and artificially overrides the ramp settings. Either that, or some will require at least 20-30% rated current flow, so they will shut down in 3-5 seconds if the motor is too small. It still shows that it works however.

It's sad that nobody at ABB can explain this to you. I used to be that guy, it appears they never replaced me... Or did you even ask?

Thx JRaef,

On a soft starter, it only controls RMS voltage via phase angle control, not frequency. It should work fine for boosting voltage to the motor, this is done all of the time in the ESP industry. So this is really about the fact that you do not fully understand soft starters.

I know that soft start only control voltage, But i just compare between softstart and VSD which is commonly used in our site which control V/F up to base speed .

On VSD No current consumed during start in case of no load test same same as my test. My question about if there effect on change voltage input only on transformer or not

Soft starters do not do anything at all unless there is a load for them to fire into, they need the current flow in order to make the SCRs function. If you were to have a LV motor and no transformer, but the motor was not connected yet, the soft starter would simply fault out on the fact that there is no current flow. But now you have added a transformer, and the transformer has magnetizing current flow. So the soft starter "thinks" this is the load, it operates, but the impedance doesn't change after the first cycle or two, so it just keeps pumping current into it at its current limit level until something shuts it down, in this case you.

I completly agree with you ,but in my case Softstart after start ramp don't trip it complete operating , My main concern why this magnetizing current disappear after Voltage reach 100% of rated voltage of transformer and if this affect transformer.

If you want to test it before connecting it to the ESP, find and connect any 3 phase motor, the size is somewhat irrelevant. The only possible issue is that you will not likely see any ramping on a small unloaded motor. It's taking place, but probably so quickly that you cannot perceive it. Most modern soft starters have what is called an "anti-oscillation circuit" that detects when a motor is t full speed and artificially overrides the ramp settings. Either that, or some will require at least 20-30% rated current flow, so they will shut down in 3-5 seconds if the motor is too small. It still shows that it works however.

I tested it before and it's already worked with high efficiency in low voltage motors.

It's sad that nobody at ABB can explain this to you. I used to be that guy, it appears they never replaced me... Or did you even ask?

THX JRaef

OK.. your problem is you are not familar with VSD's and soft starts for ESP's

Send me a private message with your contact details so I can explain in greater detail, and recommend a course of action for you.

It has been my experience that some submersible motors may not start with less than 60% of rated voltage applied and may not start even after the voltage has reached 100% of rated voltage. If the motor starts fine when started across the line, then I would talk to the soft start vendor about the soft starter specifications.

It has been my experience that some submersible motors may not start with less than 60% of rated voltage applied and may not start even after the voltage has reached 100% of rated voltage.

"Some" Then how we could know that ESP motor wouldn't start on voltage less than 60% of rated voltage, how can we make sure of this.Could you explain in more details why motor doesn't start at value less than 60% of rated voltage?

THX

My experience has been primarily with Byron Jackson/Flowserve submersible motors. The long stator/rotor versus the small diameter of the motor seems to reduce the motor's starting torque, and the weight of the rotor and the rotating assembly of the pump at rest on the motor's thrust disk requires more starting torque, than a typical non-submersible pump and motor. If you must use a soft start, you may want to consider a reactor type soft start over a solid state soft start. Talk to your soft starter vendor, they should be able to answer your questions.