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Discussion Starter · #1 ·
I am in the process of speccing a VFD to control the speed of a radiator fan for a genset.

the motor is 75hp and 480v

I am current looking at the atv630d55n4.
In this situation the VFD will only have power when the generator is running and it will lose power and soon as the generator is shut down. I’m concerned about the controller on the VFD sitting without power for extended period of time and forgetting it’s settings. How long will it take to boot up and start the fan motor? Can you even set it to start automatically after power is restored? What happens when it loses power? Some Google searches show you can set it to freewheel or slow ramp down.

I’m going to be supplying a 4-20mA analog signal to it but is there a way to set a fail safe so it defaults to full speed in case the analog signal fails? I don’t want the engine to overheat if this signal fails.

Can you program the digital inputs for start and stop commands? I imagine if the generator starts and a start command is given to the vfd then it should start the vfd with no manual input? I could also extend the engine cooldown period to give a stop command to the vfd to stop the motor 30 seconds or so before the engine shuts down to prevent it from just losing power while it’s still spinning the motor.

This seems like a bad idea to me but I have expressed my concerns and they still want to go ahead with it.
 

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To many issues with not enough information.
My personal view this is a poor application for a VFD. Shutting off the power when not running seems counter productive for the health of the drive. Possible work around if you contacted the MFG for a battery backup, maybe.

I would lean towards a soft start or a across the line contactor. A contactor removes all of the problems.
This is not a variable load so I would be wanting full RPM when running.
 

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How about a little more gritty solution if you want some speed variation for fuel savings, a two speed motor. Genset starts and it runs as a 8 pole, and when it’s heavily loaded and starts heating up, it goes to a 4 pole motor.
 

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Discussion Starter · #4 ·
To many issues with not enough information.
My personal view this is a poor application for a VFD. Shutting off the power when not running seems counter productive for the health of the drive. Possible work around if you contacted the MFG for a battery backup, maybe.

I would lean towards a soft start or a across the line contactor. A contactor removes all of the problems.
This is not a variable load so I would be wanting full RPM when running.
yah I know this is a poor application and I have expressed my concerns. They reason they want this is because it’s located up in northern Canada and it gets down to -40c in the winter time so they don’t want the fans running at full speed unless the engine is at operating temp.
 

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Discussion Starter · #5 ·
How about a little more gritty solution if you want some speed variation for fuel savings, a two speed motor. Genset starts and it runs as a 8 pole, and when it’s heavily loaded and starts heating up, it goes to a 4 pole motor.
It’s not for fuel savings it’s to prevent the fans from over cooling the engine in the winter time when it is -40c outside
 

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yah I know this is a poor application and I have expressed my concerns. They reason they want this is because it’s located up in northern Canada and it gets down to -40c in the winter time so they don’t want the fans running at full speed unless the engine is at operating temp.
Doesn't your engine have it's own t-stat, such as an AMOT? That fan should only cool the rad, not the engine.
 

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Discussion Starter · #8 ·
How about just adding an electrical thermostatic switch to the engine coolant system, then turn on the fan with a contactor at a selected temperature?
They have insisted on using a vfd to vary the speed of the fans. I can already use digital outputs in my generator controller to open and close the existing motor starter that they have but they were totally against it.
 

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Discussion Starter · #9 ·
Doesn't your engine have it's own t-stat, such as an AMOT? That fan should only cool the rad, not the engine.
Yes the engine has its own thermostat to control coolant coming from the radiator. I have explained this to them. They are concerned because they have mine haul trucks that idle for extended periods of time in the winter and the engines get to cold while idling. Unburnt fuel builds up in the exhaust and then when someone hops in the truck and drives away the fuel in the exhaust ignites and blows off the exhaust muffler. I have explained to them that their generator doesn’t idle like the trucks do and that it won’t be run low/no load because it’s a backup generator so they either backup their mine when the lose power or it’s off when they have power.

they are adamant that we install a vfd to vary the speed of these fans.
 

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We just had a project similar to this in a wastewater pump station.
The entire facility is backed up by a generator. When utility power fails, the VFDs for three individual fans are powered by the generator, if the room housing the unit reaches a particular temp, the fans power up in stages, are simply controlled by 6-dollar thermostats we bought at Grainger.

 

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Yes the engine has its own thermostat to control coolant coming from the radiator. I have explained this to them. They are concerned because they have mine haul trucks that idle for extended periods of time in the winter and the engines get to cold while idling. Unburnt fuel builds up in the exhaust and then when someone hops in the truck and drives away the fuel in the exhaust ignites and blows off the exhaust muffler. I have explained to them that their generator doesn’t idle like the trucks do and that it won’t be run low/no load because it’s a backup generator so they either backup their mine when the lose power or it’s off when they have power.

they are adamant that we install a vfd to vary the speed of these fans.
will the vfd be mounted remotely or nearby?
wont there be a heater for the engine block so that it will start in cold weather?
the electronics of the gen itself may get too cold to operate reliably at -40C
you need to prevent snow from piling up around it or it wont be able to get combustion air even if it does start
the more things that are mentioned, the more it sounds like the gen needs to be in a heated building
not a hot house but warm enough that it wont have ice or condensate on the electronics
maybe just +40F, and i dont know what that is in C
 

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I did something like this for a mine in Northern Arizona -30F not uncommon. Genset inside as well as the fan. Fan remote from the engine.
What we found with a Cat 3516 was we put louvers on the fan shroud preventing the fan from operating at full air volume, when cold. Lots of neet and expensive controls which were a pain in the ass to set right. Actual when the engine started and picked the load even in the coldest of temps the engine was at operating temp and the exhaust gases were ~ 1000F in less than 20 minutes. Quite common for that engine. The load on the engine was about 85% of capacity in the day time and at night it was closer to 90%.

Mufflers popping off haul trucks can be exciting. Seen it fortunately was on the other side of the pit when it happened.

Miners have a hard time understanding that they are painting themselves into a corner. One of the mines I worked at the middle manager and I were always fighting. He knew nothing about electrical and the equipment but he was far enough up that no one would try to persuade him he was wrong.

We lost the Pt's for the main on a unit substation, gear inside a metal house on a skid with a transformer.
So HE decided that we should pull out the breakers and change them. I got a hold of one of the old electricians and explained to him that the main breaker was wired differently on the MOC and TOC connections than the sub breakers. (VCP-W) So in the freezing cold we pulled the breakers out and played musical chairs with them. The operation failed. We really need this main to close, really needed it. So finally after 7 hours of 10 men and the paper pusher one of the old JW's looked at him and said Alan used to work for this MFG why don't we ask him.
We ended up building a sewerside cord 240V and used a generator to provide power to close the breaker. I got everyone out of the fenced yard and I closed the main. Once closed the branch breakers were easy as they had control power now. Removed the sewerside cord and headed for the shop and some hot coffee. Next shift I was called to HR for insubordination. The rest of the electricians stood up and told the truth and nothing was done. 3 weeks later my boss wanted to know how we were going to change the PT's with out shutting down the sub. I told him you weren't 13.8 bare bus inside a breaker cubical and the paper pusher wanted it done hot. I kept hearing surely there is away for you do this work hot....... Mines safetly rules specifically prohibited working any voltage over 100v hot. I demanded an 8 hour shut down and completed the job in 5 hours with me and my partner.

Do it hot my ass.
 

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You know, the entire north does not shut down when its -40.

BTW, -40 is -40, C or F.
so nobody does any thing special to gennys in the winter ?

your freezing point is 0C correct?
our freezing point is +32F,
so i thought -40F would be 32F degrees warmer than -40C
am i wrong ? or ?

edtit ... so i looked it up on the web, and yes i was wrong about -40, but not any other temp
 

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There is a factor of 5/9ths in there. A degree F isn't the same size as a degree C.

I'm no expert, but everything about this seems like a bad idea. Personally I would be worried about the vfd failing and the motor overheating. Maybe a bypass contactor of some sort would be wise and some way to sense if the fan motor is turning. Or if an overtemp switch closes it closes the bypass?
 

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Freshman year at Iowa State U was -20F. We walked a mile to classes, new dorms south of campus. The next year they had shuttle buses. Most of us had cars so we would share expenses and whom ever did not have O dark 30 classes drove.

I agree when the mercury has trouble coming out of the bulb it is very cold. Better be prepared for it. I did spend 12 weeks in the winter near Hudson's Bay. 99% was inside work and I was treated like a king because I showed up and did not grumble. Would have loved to see it when the blanket of white was gone.
 

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The Altivar drive that is mentioned, as well as several other VFDs are only spec'd down to -10C, so some sort of protection for it would be necessary.
Spec'd down to -10 means it has been tested to -10 a found to function adequately. that does not mean it won't work at -40. We have a lot of outdoor electronics here that work just fine at -40. Matter of fact, off the top of my head I haven't witnessed or heard of any that failed due to cold.
 

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so nobody does any thing special to gennys in the winter ?

your freezing point is 0C correct?
our freezing point is +32F,
so i thought -40F would be 32F degrees warmer than -40C
am i wrong ? or ?

edtit ... so i looked it up on the web, and yes i was wrong about -40, but not any other temp
Block heaters and antifreeze good to -50. Diesels need to be covered or indoors of course. Even a good block heater won't save the day there. But if the engine starts, the electronics, if outside, still work. And even indoors, the antifreeze in an outdoor rad is still at -40 when the engine is not running.
 
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