Motor VFD

Status
Not open for further replies.
A

ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
I've got a customer that has a 15hp single phase motor on an auger for a grain bin. It's a big auger and when he turns it on, it's a hard start and we're pretty sure it's not going to last like that. I'm looking for suggestions for a VFD or soft start for it. It's outside, so an outdoor unit would be handy, but if needed, I'll put it in a weatherproof enclosure. I'm not overly familiar with VFD's but I'd like something that can be easily programmed to ramp up when he hits the start switch, so he doesn't have to open an enclosure and do it with the VFD each time.

I see a lot of 3 phase VFD's for 15hp motors but not a lot of single phase ones. It should be ok to use a 3 phase on this and just use 2 phases shouldn't it, or would that throw an error or something and not let it run?

Thanks for any help
 
You can't use a VFD on a single phase motor that size because the starting winding can't stay in the circuit for more than a second and the motor has to come up to speed for the starting switch to open. Besides, any motor is a "hard start", you've got magnetic forces opposing each other sending that motion and energy straight to the metal they are connected to. The motor can handle it and the grain auger built strong enough to hold up the wear and tear of normal operation should be able to handle the force imposed on it to get moving.
 
In theory one could build a VFD type starting sytem for a single phase motor by bringing out the start winding to a separate VFD output using the start capacitor terminals. But I do not know whether it could actually improve the starting process, given the physical limitations of the situation.
 
I also wandered before if line and neutral on single phase motor could be connected to 2 out of 3 line terminals of an older mechanical overload starter or VFD built for 3 phase? Where would you get a single phase starter or overload protection device?
 
Jpflex said:
I also wandered before if line and neutral on single phase motor could be connected to 2 out of 3 line terminals of an older mechanical overload starter or VFD built for 3 phase? Where would you get a single phase starter or overload protection device?
Click to expand...
Three phase starters can be used with single phase motors. First, make sure the starter and overload block is capable of handling the single phase current.
Connect one conductor on thru to the motor as usual. Loop the second back up to the top of the starter to the third pole, then down and out to the motor. Set overloads as normal.

Won't work with VFD although some will accept 1ph in and provide 3ph out.

I have connected 15 HP single phase motors to grain bin unload augers on farms. We used 3 phase pump panels to control them via the method above. You need to make sure the voltage drop in not severe enough to prolong the start time. Max out the BCSC protection. Start it unloaded and run it empty prior to stopping. (Good luck with that)
 
While there are VFDs for SOME TYPES of small single phase motors, they are not the type that would be used on an auger or any other type of high torque application, they are only good for pumps and fans. Besides, they only go up to about 2HP max, because that’s the typical limit of that type of single phase motor. So forget the VFD idea unless you ware willing to change out to a 3 phase motor. That may be your only option though if you can’t get it to start with the single phase following ptonsparky’s advice.

Old school NEMA 3 phase motor starters can be used on single phase motors using only 2 poles of the starter and 2 heater elements, but newer types that use the IEC style OL relays need to have power going through all 3 poles, so you have to loop one pole back through.
 
ptonsparky said:
Three phase starters can be used with single phase motors. First, make sure the starter and overload block is capable of handling the single phase current.
Connect one conductor on thru to the motor as usual. Loop the second back up to the top of the starter to the third pole, then down and out to the motor. Set overloads as normal.

Won't work with VFD although some will accept 1ph in and provide 3ph out.

I have connected 15 HP single phase motors to grain bin unload augers on farms. We used 3 phase pump panels to control them via the method above. You need to make sure the voltage drop in not severe enough to prolong the start time. Max out the BCSC protection. Start it unloaded and run it empty prior to stopping. (Good luck with that)
Click to expand...
Do you mean one conductor (black line) to one phase Point of starter and second conductor (neutral white) to third phase Point of starter? Just not using b phase of starter?
 
Jpflex said:
Do you mean one conductor (black line) to one phase Point of starter and second conductor (neutral white) to third phase Point of starter? Just not using b phase of starter?
Click to expand...
I think he means your L1 and L2 of your 240 volt circuit connect to L1 and L2 of the starter, but the load side of L2 goes back up and connects to L3 and the load side of L3 would then connect to the motor so all three phases of the starter see current. L2 and L3 would just be in a loop on the same line.
 
ptonsparky said:
Start that 15 unloaded each and every time. Close the gates and runn it empty before stopping. Oversize the service. Don't skimp.
Click to expand...
This, or even check out whether there is too much VD in the supply or even insignificant size supply transformer.
High moisture grain also can be problematic.
 
Barbqranch said:
I would run it till the motor burns out. Which might be soon, or might be a very long time. Then install a 3 phase motor and a VFD.
Click to expand...
I don't think he's necessarily worried about the motor as much as he is the auger shaft having to start up at full speed every time they run a load into the dryer. I think the auger calls for a 25 hp motor and likely a VFD since it's so big. He had a 15 hp single phase so he put that on and I put an ammeter on it so he could watch how much he loads the auger to keep it from overloading. I suspect he may be better off to just abandon that and go with a 3 phase w/ VFD before something breaks.
 
ptonsparky said:
Three phase starters can be used with single phase motors. First, make sure the starter and overload block is capable of handling the single phase current.
Connect one conductor on thru to the motor as usual. Loop the second back up to the top of the starter to the third pole, then down and out to the motor. Set overloads as normal.

Won't work with VFD although some will accept 1ph in and provide 3ph out.

I have connected 15 HP single phase motors to grain bin unload augers on farms. We used 3 phase pump panels to control them via the method above. You need to make sure the voltage drop in not severe enough to prolong the start time. Max out the BCSC protection. Start it unloaded and run it empty prior to stopping. (Good luck with that)
Click to expand...
I haven't done anything with this motor yet since he was almost done with it by the time I posted last Nov., but it's going to be coming up again in a few months. Do you have a link to a pump panel as you described for the 15 hp single phase bin unload auger? I'd like to look into this a little more. Thanks.
 
ammklq143 said:
I haven't done anything with this motor yet since he was almost done with it by the time I posted last Nov., but it's going to be coming up again in a few months. Do you have a link to a pump panel as you described for the 15 hp single phase bin unload auger? I'd like to look into this a little more. Thanks.
Click to expand...
There isn't really any such thing you will find looking at their marketing information. You will need probably one with at least a 25 maybe 30 HP rated motor contactor (three phase) in it to do like he said or have something custom made for the purpose. You just won't find stocked and/or catalog number items with a two pole contactor designed for a 15 HP single phase motor - simply not enough demand for such a product for them to go to any effort to make them be readily available. Use of the 25 or 30 HP three phase setup likely will cost less and be more readily available.
 
The trick, if there is such a thing is to look at the starter itself. It will have HP ratings for single and three. Make sure the single phase rating equals or exceeds your 15 HP at the applied voltage. The overload block must also have the current rating for your 15. I have on occasion had to buy that separately. My local supplier usually had what I needed on hand. It was the advantage of being in a rural area that moves a lot of PPs, and having a good working relationship with those wholesalers.

I used CH primarily but SQ D and Siemens were options.
 
ammklq143 said:
I've got a customer that has a 15hp single phase motor on an auger for a grain bin. It's a big auger and when he turns it on, it's a hard start and we're pretty sure it's not going to last like that. I'm looking for suggestions for a VFD or soft start for it. It's outside, so an outdoor unit would be handy, but if needed, I'll put it in a weatherproof enclosure. I'm not overly familiar with VFD's but I'd like something that can be easily programmed to ramp up when he hits the start switch, so he doesn't have to open an enclosure and do it with the VFD each time.

I see a lot of 3 phase VFD's for 15hp motors but not a lot of single phase ones. It should be ok to use a 3 phase on this and just use 2 phases shouldn't it, or would that throw an error or something and not let it run?

Thanks for any help
Click to expand...
Reply for outdoor enclosure. I have worked on 40 to 100 HP VFD'S that were outdoors in a NEMA 4 enclosure. Every cabinet had a air inlet with a filter at bottom right then a exhaust fan top left. Also had a small heater and a thermostat think set around 50 degrees to guess keep humidity down in the winter. I was a commercial sparky for 50 years and never came across a single phase motor more then 5 HP . Did you check the voltage before the 15 HP motor starts & while running? If three phase was available that would be the best way to go.Can remember years ago when a small machine shop purchased a single phase 5 HP motor instead of a three phase motor. Believe it cost at least 30% more. Did a quick check with graingers a 5 HP single phase motor cost almost as much as a 15 HP Three phase motor.
 
garbo said:
Reply for outdoor enclosure. I have worked on 40 to 100 HP VFD'S that were outdoors in a NEMA 4 enclosure. Every cabinet had a air inlet with a filter at bottom right then a exhaust fan top left. Also had a small heater and a thermostat think set around 50 degrees to guess keep humidity down in the winter. I was a commercial sparky for 50 years and never came across a single phase motor more then 5 HP . Did you check the voltage before the 15 HP motor starts & while running? If three phase was available that would be the best way to go.Can remember years ago when a small machine shop purchased a single phase 5 HP motor instead of a three phase motor. Believe it cost at least 30% more. Did a quick check with graingers a 5 HP single phase motor cost almost as much as a 15 HP Three phase motor.
Click to expand...
I've only seen the larger 1 phase motors for augers etc in the last few years. Grain Aeration fans, a long time.

These things are hard to start. Everything needs to be maxed with as minimal startup load as possible.
 
Status
Not open for further replies.
Top