Soft Start for Motors

DanS26 · May 2014

The soft start motor technology has been around for awhile (at least ten years) but we hear very little about this technology.

Some companies are claiming as much as 70% reduction in LRA. If that is true we have been over sizing generators, etc. for these start up amps which possibly can be mitigated. Why install a 17kW generator when a 10kW would work just as well. Should also apply to sizing solar systems etc, for maximum draw.

Don't confuse this technology with hard start which has been around even longer.

Anyone out there with soft start experience?

DanS26 · May 2014

Re: Soft Start for Motors

No response, so I'm assuming that there is very little experience with soft starts.

I'm going to take the plunge and install a soft start on my 2 1/2 ton AC unit. This unit is part of my critical circuits powered by a 10 kW generator. The generator will start the AC but will seriously bog down, almost to the point of stalling. I don't think this is good for either the generator or the AC motor/compressor.

Generator is rated for 60 LRA and 40 RLA. The AC nameplate says 72.5 LRA and 15 RLA and thus there is the problem. The soft start is supposed to reduce the AC LRA to under 30. Another benefit is the light dimming upon start-up will be lessened. We will see.

I'll post the results here later.

mike95490 · May 2014

Re: Soft Start for Motors

I think the problem is, each motor and load, presents a unique configuration, which requires an individually tuned approach, not a generic "box".

BB. · May 2014

Re: Soft Start for Motors

Wayne from NS Canada did a neat solution for his refrigerator(s) to run on a 300 Watt MorningStar inverter. As I recall, fter tuning the motor start capacitor value, he add a timing circuit and auto transformer that drops the voltage to the compressor by 20% or so.

This does two things... One, the reduced starting voltage reduces current through the motor, and second, the 20% drop in starting voltage through the transformer also supports ~20% more starting current from the AC inverter. Once the motor is somewhat up to speed, he switches back over to 100% AC inverter output. Allowed him to run a refrigerator+freezer on a single 300 Watt (600 watt surge) AC inverter.

He also added logic so that only one appliance ran at a time on the AC inverter.

Really an "out of the box" idea. Not sure I would want to try it on a $5,000 AC System.

-Bill

Cariboocoot · May 2014

Re: Soft Start for Motors

mike95490 wrote: »

I think the problem is, each motor and load, presents a unique configuration, which requires an individually tuned approach, not a generic "box".

Bingo!

And since the majority of end users have the 'unlimited' power of the grid to run things from most manufacturers are not going to bother with the added expense of soft-start technology.

jonr · May 2014

Re: Soft Start for Motors

How much you can reduce voltage during start depends on the motor and the load. 20% is a pretty good bet, more in some cases. I'd look for something adjustable. Which one are you going to use?

Fixing the power factor during start is a different thing, but it should also be considered (heating up the wires while starting adds to the load).

DanS26 · May 2014

Re: Soft Start for Motors

jonr wrote: »

How much you can reduce voltage during start depends on the motor and the load. 20% is a pretty good bet, more in some cases. I'd look for something adjustable. Which one are you going to use?

Fixing the power factor during start is a different thing, but it should also be considered (heating up the wires while starting adds to the load).

I'm installing a device called a Sure-Start6 manufactured by Hyper Engineering. They started out on Australia about ten years ago. Open a facility in Ft. Wayne IN to service the North American market. I found out about the product thru a Generac rep. As far as I know they make three products for the small motor market...one for 120 v motors and two for 240 volt motors sized based on the RLA of the motor. So it is not a one box fits all type of system.

Attached is their Specification Catalog, just released. I think it is a good read if you are interested in this kind of stuff......

Attachment not found.

Blackcherry04 · May 2014

Re: Soft Start for Motors

DanS26 wrote: »

I'm installing a device called a Sure-Start6 manufactured by Hyper Engineering. They started out on Australia about ten years ago. Open a facility in Ft. Wayne IN to service the North American market. I found out about the product thru a Generac rep. As far as I know they make three products for the small motor market...one for 120 v motors and two for 240 volt motors sized based on the RLA of the motor. So it is not a one box fits all type of system.

Attached is their Specification Catalog, just released. I think it is a good read if you are interested in this kind of stuff......

Attachment not found.

It looks enough like the Dometic Smart Start that they probably manufacture it for them. I'd like to try one, but it's hard to justify $400 starter on a $100 A/C, but under the right circumstances, $400 would be cheap.

Where did you find one for sale ?

waynefromnscanada · May 2014

Re: Soft Start for Motors

DanS26 wrote: »

Attached is their Specification Catalog, just released. I think it is a good read if you are interested in this kind of stuff......

Attachment not found.

This does indeed look very interesting. I'd love to have one to play around with.
Thanks for sharing!

DanS26 · May 2014

Re: Soft Start for Motors

Blackcherry04 wrote: »

It looks enough like the Dometic Smart Start that they probably manufacture it for them. I'd like to try one, but it's hard to justify $400 starter on a $100 A/C, but under the right circumstances, $400 would be cheap.

Where did you find one for sale ?

Here is where I bought it:

http://www.gen-pro.biz/#!shop/cs2b

Paid $219 and they offered a $30.66 discount, S&H was $9. Total net price delivered to my door $197.34

Cariboocoot · May 2014

Re: Soft Start for Motors

DanS26 wrote: »

Here is where I bought it:

http://www.gen-pro.biz/#!shop/cs2b

Paid $219 and they offered a $30.66 discount, S&H was $9. Total net price delivered to my door $197.34

So are you going to open it up and show us what's inside?

Blackcherry04 · May 2014

Re: Soft Start for Motors

DanS26 wrote: »

Here is where I bought it:

http://www.gen-pro.biz/#!shop/cs2b

Paid $219 and they offered a $30.66 discount, S&H was $9. Total net price delivered to my door $197.34

Thats a good price based on the Dometic unit, about 1/2. I see now it has the wiring attached just like the Dometic. I had thought about getting one, but decided a Inverter with Generator Support made more sense at the time, Guess I could still try one. Thanks for the Information.

DanS26 · May 2014

Re: Soft Start for Motors

Cariboocoot wrote: »

So are you going to open it up and show us what's inside?

The "engineer-wanna-be" in me would like to do that. Their literature is pretty clear, open the box and it voids the warranty. But that has not stopped me in the past with these kind of things.

I'll get my Fluke out and make some before and after readings. I just can't hardly believe a 70% reduction in LRA, I just have to see it to believe it.

Cariboocoot · May 2014

Re: Soft Start for Motors

DanS26 wrote: »

The "engineer-wanna-be" in me would like to do that. Their literature is pretty clear, open the box and it voids the warranty. But that has not stopped me in the past with these kind of things.

I'll get my Fluke out and make some before and after readings. I just can't hardly believe a 70% reduction in LRA, I just have to see it to believe it.

I admit to having a problem with the claimed reduction in current at no loss of starting torque. I suspect they are adjusting the resistance so that it is high at what would be peak current demand and low and peak Voltage on the waveform. That is no simple task to accomplish. Essentially a fast-acting reactive power factor correction.

Blackcherry04 · May 2014

Re: Soft Start for Motors

Dometic has plenty of Videos. It's big in the marine business. I see lot's of RV guys using them. There use to be a picture of one opened, I couldn't find it.

http://www.dometic.com/enus/Americas/USA/Marine/Dometic---Air-Conditioning/Accessories-for-Dometic-Air-Conditioning/products/?productdataid=106954

They say it takes 10 starts to make the adjustment to the starting adjustments automatically.

Cariboocoot · May 2014

Re: Soft Start for Motors

Should we note for people reading this that it will not reduce your electric bill at home?
Good for getting motors going when they have to be powered by the VA output of an inverter or generator though.

jcheil · May 2014

Re: Soft Start for Motors

Cariboocoot wrote: »

Should we note for people reading this that it will not reduce your electric bill at home?
Good for getting motors going when they have to be powered by the VA output of an inverter or generator though.

Think it would help with PF correcting of the Iota chargers?

Blackcherry04 · May 2014

Re: Soft Start for Motors

Where they are a real Boom is in the RV roof mount A/C units, they are all 13.5-15k, BTU units and are to big for a Honda EU 2000. They will run, but it cannot start on them. With this they will.

My interest would be if they will start a A/C compressor in ECO mode without faulting. If you have to run the generator with ECO off, so the compressor can cycle, you don't have much. Thats where Gen Support really shines, it picks up the deficit.

Cariboocoot · May 2014

Re: Soft Start for Motors

jcheil wrote: »

Think it would help with PF correcting of the Iota chargers?

Probably not due to the "learning sequence": a motor start-up will be fairly consistent so the device can 'memorize' those characteristics. The Iota is going to run differently because the SOC of the battery it connects to will not always be the same when you start charging.

The problem of the large inrush current to the capacitors ... Hmm. Interesting question.

jonr · May 2014

Re: Soft Start for Motors

jcheil wrote: »

Think it would help with PF correcting of the Iota chargers?

I don't know that the lota is doing, but I suspect it may distort the waveform (ie, not a phase shift that is easily fixed). Only filtering (like a dv/dt) will partially fix that.

Inrush due to capacitors or inductors could probably be fixed with a thermistor.

DanS26 · May 2014

Re: Soft Start for Motors

Since this is the "Advanced Solar Electrical Forum" lets have a little fun with this thread.

As you all know I'm going to install this soft start device later this week. Sooooo the "engineer-wanna-be" in me (yes, my alter ego) just has to pre-plan the operation by perusing the installation schematic. Here it is:

Attachment not found.

There is an error in this schematic, really an omission. I'll buy a virtual beer to the first person to identify the omission.

Blackcherry04 · May 2014

Re: Soft Start for Motors

I noticed something odd about the schematic on the Sure Start and the Dometic unit that is worth mentioning. Dometic uses the ( L1- hot ) as the common on the compressor and runs their soft start backwards to the way the Sure Start does with the neutral. Just a word of advise when you wire it up, look careful at your unit.

DanS26 · May 2014

Re: Soft Start for Motors

Blackcherry04 wrote: »

I noticed something odd about the schematic on the Sure Start and the Dometic unit that is worth mentioning. Dometic uses the ( L1- hot ) as the common on the compressor and runs their soft start backwards to the way the Sure Start does with the neutral. Just a word of advise when you wire it up, look careful at your unit.

Yes, I noticed that too.

notes · May 2014

Re: Soft Start for Motors

Crankcase heater wired incorrect also. You may also want to add a solenoid drop valve in your liquid line. Use a 24 volt coil, powered up on a call for cooling and drops out when thermostat is satisfied. Stops refrigerant from migrating back into cooling coil and less suction gas on compressor valves, easier start up. Carrier has been using this method for years in the residential market. Drops start amps quit a bit.

DanS26 · May 2014

Re: Soft Start for Motors

notes wrote: »

Crankcase heater wired incorrect also. You may also want to add a selinoid drop valve in your liquid line. Use a 24 volt coil, powered up on a call for cooling and drops out when thermostat is satisfied. Stops refrigerant from migrating back into cooling coil and less suction gas on compressor valves, easier start up. Carrier has been using this method for years in the residential market. Drops start amps quit a bit.

Yes, its a Carrier system, but the system does not have a drop valve. Maybe too small for that type of device, only 2 1/2 ton.

I see the point, reduce the pressure and the compressor will start easier.

Good catch on the crankcase heater wiring circuit, but that is not the omission that is obvious and critical to the AC operation.

I see your point, the 240v return is directed to T1 rather than T2 on the crankcase heater option circuit....a wiring error. You get a six pack for finding a wiring error.

Good catch!!

Blackcherry04 · May 2014

Re: Soft Start for Motors

I had a nice conversation with Tim Fiedler from Gen Pro ( tim.e.fiedler@gmail.com ) about the Sure Start. He seems to know the product well and what it does and what you can expect from it and how to use it and Install it. They are teamed up with Emerson, Genrac, Dometic and others for OEM products. He only had 240V units on the web site , so is having a 120V unit dropped shipped to me and will add them. He was not really up on the issues with Solar and has offered to give advise on how inrush problems can be solved. He is well aware of the economic issues with a $200 product, but depending on what you have and what you need it may be a bargain.

DanS26 · May 2014

Re: Soft Start for Motors

OK Coot here ya go. The chip with all the good stuff is buried below. That programming could be worth a fortune.

Attachment not found.Attachment not found.Attachment not found.Attachment not found.

So are you going to open it up and show us what's inside?

Cariboocoot · May 2014

Re: Soft Start for Motors

The big cap is no surprise. Good that they've got a fuse in there.
Hard to tell what else it's made of. Control chip underneath, okay, and ... a couple of triacs? Some of the components must be for supplying power to the chip.

It does appear to be a reactive unit, although how it is gauging current vs. Voltage I do not know. Small current transformer there? It would be interesting to reverse-engineer. But I'm not so young as I once was and neither is my eyesight.

Blackcherry04 · May 2014

Re: Soft Start for Motors

One thing that Tim told me was that on it's first start that it is wide open and that it will actually be cutting it's self back as it learns the requirements of your system. Thought that I might post it in case your going to use a meter to check the inrush as it will change.

Ken Marsh · May 2014

Re: Soft Start for Motors

Interesting thread, wish you success.

A VFD is a different approach to the problem.
They start a 0 amps when the motor is at 0 rpm and current ramps up in proportion to the rpm.
This does require you install a 3 phase compressor.
But I probably will have the system decharged anyway to install domestic water heat.

The VFD also allows you to control the speed of the motor which can bring savings
particularly in the parts of the year when you need hot water but do not need heat or cool.
Three phase motors usually pick up some 20% better efficiency.

DanS26 · May 2014

Re: Soft Start for Motors

Sorry guys, I have not installed the soft start yet.

My son has my Fluke meter. Hopefully he will return it soon.

I want to get good readings on the max amp draw before and after.

Soft Start for Motors

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