Instrument/Electrical

I'm interested in soft starting, but:

"The current 40 H.P. motor is part winding. I am not sure but I think we would save energy and wear and tear on the motor. Management wants to see something in writing, I am not 100 percent I am correct in my thinking and not sure where to find the 411 I need." is not clear enough.

Regards... Samak

Yes, things were clear until I reached the part about the "part winding" and the "411". I have no idea what these mean.

Soft-starters are not necessarily energy saving devices. In a way, they may save some energy if you configure them for current-limit starting. This is where the unit starts the motor by limits the starting current. Once the running speed is achieved, however, the motor will still draw the same current as before, so no savings there.

Therefore, you can say that there will be some savings on power use but only on starting. The other savings is in the wear and tear on the motor, turbine, and structure.

If you want to save electricity, you should use a variable-frequency-drive and run the turbine at a lower speed. Whether your turbine can be allowed to do that is known only by you.

"In a way, they may save some energy if you configure them for current-limit starting."

Soft starters don't save energy in the starting inerval even current limiting feature is used. The required amount of energy to drive the shaft from stand still to full speed is fixed, but it is absorbed gradually from the supply via current limiting feature or other techniques.

Please,visit the thread "Soft Starter / Energy Saving"

Good luck... Samak

There would not be any power savings by changing to a soft starter. However if by part winding you mean Star Delta starting then there could be some argument regarding making the motors life less arduous. SD starting on pumps can cause very high current spikes at change over if the timing isn't spot on. I have no idea what 411 has to do with anything. As previously mentioned VFD may offer cost savings on power usage. BUT be very carefull dependant on the static head, pipe line losses etc you could find that turning the speed down just a little drops the flow to an unacceptable level and the VFD will never pay for itself. Give all the facts and figure's to the pump company and they could help you answer this.

Quite.

The shaft power required by any fluid mover is the product of the volumetric flowrate and the rise in pressure, expressed in consistent units. A soft-start simply reduces the 'shock' to the motor and cabling upon starting the motor, nothing else.

Working-up a justification for a soft-starter on the basis of energy savings alone would be impossible. However, if the shock of starting this pump were to take out some critical services elsewhere by nature of its starting current, or would point to an expensive cable replacement project as a result of needing a bigger one by nature of its starting current, then a soft-start might just save the day as being the cheapest of three options; one might be able to justify the investment on that basis, perhaps?

You may want to contact a few soft start manufacturers as they should have salesmen and product info to help understand what their product offers. I would guess power savings would be minimal but wear and tear at start-up may make it worthwhile also may reduce the pressure surge from the pump by a slower spool up.

FYI - 411 is the number dialed in the US for directory assistance or information and has come to be a slang word for info. So the poster is merely looking for info on his thoughts about soft starters.

Shawn

<FYI - 411 is the number dialed in the US for directory assistance or information and has come to be a slang word for info. >

........which simply underlines the need to eliminate local slang and undefined acronyms in a global forum such as CR4.

........which simply underlines the need to eliminate local slang and undefined acronyms in a global forum such as CR4.

Or people can simply explain what was meant (as was done in this thread) instead of putting silly rules into effect to limit what people can or can not say. I'm sure identifying contextual queues is taught all over the world.

Not in Basildon.

I may be the only one ancient enough not to 404 when you mention part winding motors. Not stated is that you plan to also replace the motor, I hope. Connecting a PW motor to energize both coils at once and then use a soft start will not get any savings. However nobody I know makes a PW motor that meets NEMA premium efficiency standards. Changing out the motor may have a payback; check with your motor supplier. Check with the utility whether you are still required to have reduced inrush starting at this site.

I have started 100 HP pump motors directly across the line, so 40 HP is certainly no problem. As the motor starts from zero speed, the load starts from zero and goes to maximum when the motor speed reaches maximum.

By your Voltage and "411" I suspect you are in the USA. If so, here is the contact "411" of an VFD Guru for ABB Drives:

Robert Hansen, Product Manager-ABB Drives, Mgf. Rep for Carmody Co. Inc., rhansen@carmodycompany.com, www.carmodycompany.com, 1-800-333-3103, Cell 1-206-979-0586, Fax 1-206-763-4084.

Hope this helps!

Mr. HandyMan

Hello

May I invite all of you and your friends to the thread "Soft Starter / Energy Saving"

Thanks... Samak

Friend--

A soft starter will give you two benefits---reduced mechanical shock to the system when the motor starts, and the possibility to reduce the inrush current.

You didn't mention if this was a 50%-50% part winding motor or some other ratio of division of the motor's running current between the two windings. However, I suspect it is a 50/50 as these are much more common. Others have noted that you would have to use a single soft starter and wire it so both windings are energized simultaneously. I believe this is correct. You would still have to maintain the separate running current protection for each winding, even though the soft-starter normally includes its own overload sensing.

At full speed, there is still a modest amount of energy loss in the soft starter, so sometimes people will design in bypass and isolation contactors for it. When they transfer the load to the bypass mode there is a risk of momentary mechanical shock to the system, so this needs to be considered. Such an installation will require a little more room and require also that the contactors be mechanically as well as electrically interlocked. Controls will need additional timing, functions to do this.

If you are having serious worries about the mechanical stresses on the pump, then a soft starter is one good way to help. Variable Frequency Drives also do this, with additional benefits of energy savings when the pump is running with a reduced load. If you have to throttle the flow down (with a valve or other means) then a VFD is a good and energy saving alternative. Many threads have been posted here regarding application benefits and concerns, so I won't repeat anything here.

Regards--JMM