3 phase Motorboss soft start

[apa6eightball]

I am designing a new starter/control system for a 3000 psi hydraulic power supply with a 3 phase, 460Vac 100hp motor. I have been looking for something more efficiant than a star delta and found the Motorboss soft starter sold by Advanced Motor Power,

http://www.advancedmotorpower.com,

has anyone ever used one of these before?

 

[CJCPE]

The Motorboss soft starter may be a perfectly good product, but the energy savings claims on their web site are exagerated. Your best course of action for potential energy savings would be to buy the most efficient motor that you can find. At 100 Hp, 1800 RPM, you should be able to find a motor that is above 95% efficient between half-load and full load.

Read the following FAQs and look through previous discussions on this forum.

Energy Savers for Induction Motors faq237-971

How to select the correct motor starting method - Overview faq237-1029

What is a Soft Start? faq237-1064

 

[apa6eightball]

Thanks for your response and the FAQ links, CJCPE, they offer some valuable information. We are using a PLC to control a valve to dump the pressure at start up to reduce the load, then ramp the pressure up after the motor is at full speed. We are using a compensted pump to handle an anticipated changing flow demand and that is one of the reasons to consider a starter like the motorboss. Thanks again

 

[rbulsara]

Consider a varaiable frequency drive (adjustable speed drives) if the flow demand is changing often. This will give you the soft start as well as real energy savings at reduced speed when demand is low.

 

[jraef]

As soft starters go, I have looked at the Motorboss and was not impressed with the specifications. There are plenty of very good products from reputable companies out there who have a lot more experience making soft starters and are not prone to making wild claims about energy savings.

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[cbarn24050]

A vfd is the way to go here if your pump has alot of running hours each year. With proper control you will save huge amounts of energy over a standard motor/starter arrangement.

 

[LionelHutz]

We looked at a Motorboss at a customers site. There was no current feedback. I found that curious since I had believed the unit would need current feedback to properly perform the Nola energy saving function. The unit would just run at a fixed reduced voltage as far as we could see. There was a pot to dial in the amount of "energy savings".

 

[cbarn24050]

hi lionel, these kind of starters dont use current feedback to control the "energy saving" function, its done by compareing the crossing point of the supply with the turn off point of the thyristor. They do usually have a current transformer for the current limit function so I'm a bit surprised there isn't one fitted.

 

[CJCPE]

If the "compensated pump" controls flow with some kind of bypass valve arrangement, a variable speed flow control system will be much more efficient. If a variable displacement pump is used to control flow, a variable speed drive would not improve the efficiency.

 

[jraef]

LionelHutz,
cbarn24050's explanation is correct, except it is also possible to indirectly calculate current that way as well. Allen Bradley did that for years with their SMC product line (prior to the SMC Dialog and Flex), even to the point of providing overload protection. It's a very old technology dating back the the earliest days of soft starters, but most manufacturers abandoned it for the following reason. Once a bypass contactor pulls in you lose ALL ability to sense current. That is why the AB SMC's required an "adaptor module" and an external OL relay if you used a bypass contactor. The Powerboss apparently has the same problem, that is why they barely mention the issue of using bypass contactors; they require additional hardware for protection AND they completely negate their "energy saver" function, the main thrust of their sales pitch.

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[apa6eightball]

Thank you, gentlemen, for all of your valuable input. I am going with a VFD for this application, although I may try a motorboss for a future, smaller and less critical application just to see how they work.........apa6eightball

 

[GGOSS]

As a soft starter, the Motorboss product offers very basic open loop controlled voltage soft starting. I suspect you would get a much higher level of soft start functionality, and a better buy price by going to one of the majors.

 

[LionelHutz]

Intersting, I'm going to have to take a look at how to calculate current by comparing phase crossing.

I agree with GGOSS though, the Motor Buss functionality as a soft-starter seems weak and the major manufacturers all have an energy saving function. The price seems high for what you get.

 

[GGOSS]

To the best of my knowledge it is not possible. With regards to motor overload protection and AB, I can confirm they introduced it with their SMC Dialogue products and have continued to offer the functionality in the SMC 3, SMC Delta & SMC Flex. The AB STC, SMC2 and SMC Plus products did not offer motor overload protection.

Regards,
GGOSS