Lathe motor won’t turn over on solar

[SCClockDr]

I'd suspect a current surge in phase with voltage droop. The inverter needs time to stabilize when hit with a large demand. The grid has gigawatts of available power vs a 5Kw inverter.

 

[SCClockDr]

You might see an improvement using an Easy Start device. They are pricy but very effective, it can lower surge current by as much as 70%.
I'm a very satisfied customer I can start & run a 15K RV AC unit on a EU2200Si Honda in ECO mode, with other minimal loads running.

 

[Hedges]

If you could get another induction motor spinning first, it might deliver a kick to start the lathe. If you used a brush type motor like a drill or grinder to start a 2 HP motor spinning, then connected AC to the 2 HP motor, then turned on the lathe, that might work.

So you got it working by bypassing an over-current protection device. Because your inverter can't supply the starting current demanded, the motor is taking longer to start than it should. Things could overheat that way. Motor starters have heating elements that limit/sense high starting current and trip a breaker to protect the motor. If you're going to bypass the protection, do so with a manual "push to start" switch so protection is otherwise left in place.

Just spinning the lathe chuck with a rubber wheel on a drill might reduce current and shorten starting time sufficiently.

 

[Supervstech]

Just spinning the lathe chuck with a rubber wheel on a drill might reduce current and shorten starting time sufficiently.

Hey! I said that two months ago!

 

[FilterGuy]

I still think the root cause of the problem is the 40 Ft extension cord. With the start-surge the voltage drop could be considerable. This in turn could cause the start surge to last longer.... popping the circuit protection.

 

[Hedges]

I still think the root cause of the problem is the 40 Ft extension cord. With the start-surge the voltage drop could be considerable. This in turn could cause the start surge to last longer.... popping the circuit protection.

Could be, but I think the problem is the inverter, not the extension cord.

On a mountain property I unrolled 250' of 10 AWG UF, from an electrical outlet to a South Bend set up inside a cargo container. Actually, to a trailer first, then extension cord to the lathe.

Consider a 100' round-trip 50 ft, 16 gauge extension cord:

Table of equivalent AWG Wire and Resistance per foot

AWG Chart of Approximate equivalent Cross-Sections of Wire, American Wire Gauge by Resistance per 1000 feet

www.interfacebus.com

That would be 0.4 ohms. Try to put 50A starting current through it - that's 20V drop, so 120V in gets 100V out. Probably enough to start.

Sunburnt said the inverter was in another room. Probably going through 12 AWG house wiring, not an extension cord. That's 0.16 ohms and 8V drop.

But sure, thicker gauge and shorter is better. I have many 12 AWG cords besides the UF I sometimes use for semi-fixed applications.

The inverter on the other hand probably can't supply 6 kW for more than a few milliseconds and voltage collapses. Induction motors are the problem; brush-type would work better. I had thought a VFD and 3-phase motor would be the way to go but its switching upset one of my inverters (maybe an inductive filter on the input would fix that.)

 

[evad]

Put a volt meter across the motor leads. If the voltage sags during the start up but is near 120 volt once it is running then holding the start button is a solution if its dropping to 105 or so running with a load then you need to find out where you are dropping the voltage.

 

[DThames]

Hey! I said that two months ago! (give it a spin first)

Indeed. Part of that huge inrush current goes into the start winding circuit. Spinning it a bit before you hit the power switch reduces the starting amps. While testing motors in a manufacturing plant, if the motor didn't want to start, if I could spin it get it to start, read the idle run amps, you could test to see if the "run" winding okay and if so, tell the repair station that the problem was in the start winding circuit. Or you could prove the "run" winding was the problem, like a reverse connected coil.

A great deal of forethought and caution is needed trying to put spin into something that will then start turning under it's own power. Anyone doing this needs to think through what will happen when it starts.

 

[RCinFLA]

Did the battery cable to inverter gauge get mentioned somewhere? If too small gauge that would be easiest solution.

I had a 5/8 HP well pump that just made it on startup with a 4kW 48v inverter. with 2/0 battery lines.

Start current can be greater then locked rotor nameplate as locked rotor is rated at lowest AC line voltage to ensure maximum breaker size on a branch line. Your inverter output is likely initially sagging but asking for more motor starting to make it up just compounds load on inverter.

Hard start cap kits can actually make things worse. They are intended to create more start current from a low voltage AC line. You might try an AC motor soft starter which has adjustments to control a triac (dimmer-like) ramp up. For induction motors you normally can only reduce peak startup surge current by extending the length of time of the lower surge current. No free rides. Inverters only allow a given surge current level for a given period of time before tripping off. The higher the surge current the shorter the period before inverter trips off. Extending the length of time of a lower surge current may not gain anything.

An old brush type AC motor would be no problem to soft startup.

 

[Hedges]

If your lathe is belt drive, release the belt tension when starting.

 

[Zil]

Get a soft start device as used for air conditioners in RV's. Why fuck around putting your expensive equipment at risk?

 

[Santa Fe Big Sky]

You will probably need to consider a soft starter. Not cheap. Two ways to start a motor without the high current draw. You can lower the a/c voltage and step it up slowly until the motor is at full speed or you can change the hz to start at like 30hz and slowly step it up to 60 hz. Either way it takes some fancy electronics and with you motor size might not be cheap.

 

[RCinFLA]

I have not used an Easy Start device but I believe it to be a combination of a softstarter and starting power factor correction. The five start 'training' is to find a reasonable softstart ramp profile and perhaps learn a reasonable power factor correction setting The maker claims that it works with ECO mode on inverter generator. This is a bit of slight of hand as it has control to start the A/C blower first which brings gen out of ECO speed to full speed prior to starting compressor..

At startup, an induction motor is near locked rotor current and very inductive, lasting for spinup time. Power factor correction can help a lot but must only last the time it takes to spin up the motor. Tricky part of power factor correction is it needs to avoid getting too close to resonance (PF of 1.0). Getting too close to resonance can create destructive voltages. I have played with both softstarting and startup PF correction. What scared me off of the startup PF correction is it changed with temperature of windings of compressor motor which gets pretty warm after running for a while and I did not have a capacitor value selection to back down to a safe amount of PF correction.

I think I paid $250 for a fancy industrial softstarter but that was over 10 years ago. Really just a high current triac dimmer with adjustments for initial dimming level and ramp up time slope adjustments, on a big heatsink.

Actually what scared me off was what my wife would do if I screwed up the air conditioner in July.

 

[RCinFLA]

Did a one page explaination diagram on these softstarters if you are interested on how they work.

All will work, just have to get the starting cap approximate correct value. Three to four times permanent run cap value.

MicroAir EasyStart sell a bare controller board you have to supply your own starter cap. (and case). No warranty no return but saves $100.

 

[Chris42404]

In terms of a VFD for that size of motor, you might be able to look at a MicroAir soft start controller. They are typically used for roof AC units in motorhomes, but they are fantastic for mitigating the inrush current when the AC’s compressor fires. I’ve played with these several times and they are tanks. The controllers are about $400 I think, but they completely smooth out the startup current draw when the compressor starts up. The controller lets you easily start a 15,000 BTU AC (14 amp compressor draw) on a Magnum MS2812 2800w pure sine wave inverter charger. Inverter never skips a beat.

 

[Chris42404]

You might see an improvement using an Easy Start device. They are pricy but very effective, it can lower surge current by as much as 70%.
I'm a very satisfied customer I can start & run a 15K RV AC unit on a EU2200Si Honda in ECO mode, with other minimal loads running.

I didn’t see your post until after I said the same thing. The Easy Start controllers are very handy items. I’ve played with several of them myself and they have never skipped a beat for me. A lathe as opposed to a compressor is kind of off of an off label application, but I bet it would work

 

[RCinFLA]

If the motor does have a centrifugal or other start capacitor dis-engage switch it should be bypassed with these softstarter/starter boost cap boxes. The softstarter/boost cap boxes takes over the dis-engage switch function.

For a motors with just a start capacitor and cutout switch, I would begin with same cap value in the softstarter. You might try increasing value by 50% to see if you get more improvement in startup surge current. Just do not want to get too high as there may be a small chance of damaging motor start windings. Optimum value would likely be 90 deg current phase shift on start winding relative to run winding current. That takes hall effect sensors with two channel scope to measure. You have to move some jumpers to clear previous profile training and start over training with factory initial settings if you want to play with different startup capacitor values. There is on-line docs on how to reset training.

I just put a EasyStart ASY-368 on my 4 ton central air cond with Copeland scroll compressor. Copeland scroll compressors are rugged but are notorious for high startup surge current.

As stock setup (240vac)
Startup surge = 203 amps for 400 msecs, run 14.1 amps.

With EasyStart 368
1st training startup surge = 102 amps
2nd training startup surge = 93 amp
3rd training startup surge = 84 amp
4th training startup surge = 73 amp
5th training startup surge = 64 amp (noticable startup 'grunting' )

Final auto-selected startup profile = 73 amps ( 64% reduction )

I probably could squeeze a little more out of it with a slightly larger value start capacitor. My inverter had no problem with the 73 amps.

The training is just running through various softstarter ramp profiles via Triac (voltage dimmer) control.

These boxes are a coordinated combination of softstarter and hardstart capacitor. A hard start cap kit is used when having start up problems with low AC line voltage. Alone, a hard start kit may increase startup surge current. A softstarter is just a voltage dimmer ramp up. They work well for three phase motor but for single phase motor they lower startup surge but extend the length of startup time so for an inverter, a softstarter alone usually does not help enough because the lower surge current lasts too long in time.

 

[softdown]

I did not muscle through the replies but had a similar problem when starting with solar in 2010. Assuming a robust 12-15 amp motor and the accompanying starting surge - you need several things:
A battery/batteries that can supply high surge current
Cabling that can supply high surge current. This may involve ~2/0 AWG Cu at 12 volts for example.
Very large inverter. I was using a lot of power tools building this shop. One of the first things I had to do was return an ~3000 watt inverter and get an ~5000 inverter. Inverter surge current is important. Memories are 10 years old - numbers could be off.

Using too small of inverter can damage your motors as well.

Then you have the soft start option a few mentioned.

Being a seasoned tool addict I buy a LOT of big, used tools made in America and Japan for nostalgia and practicality. A decent way to test the health of a large 12-15 amp motor is to plug it in. If it literally jumps into action with the ON button, that is a good start. But it could also have a soft start motor. I suspect Makita employs that at times.

 

[eprotiva]

power factor, you need some ntc resistors inline to eat the inrush.

 

[Zil]

Sunburnt solved the problem in Apr 9, 2020. Has not been back. Maybe lose clothing caught in the lathe that now turned.

 

[Hdonly]

I assume it is a capacitor start motor. Possibly your start capacitor is failing.

 

[8_Hz_WAN_IP]

I have a hobbyist lathe with a single-phase 115v motor of 3/4 HP. This motor turns on normally when I am connected to grid power, and VERY occasionally when connected to solar. But most of the time on solar the motor does not spin up. I’m wondering what I can do to allow it to start on solar.

My solar system, when running on batteries alone, can produce at least 70 amps output for several minutes at least (I have tested this with an electric heater and the battery monitor shows 70 amps coming out of the batteries when the heater is on). I wouldn’t think the 3/4 HP lathe motor would take anything like that for startup amperage, but perhaps it is possible.

Could adding some additional start capacitors to the motor cicuit help in this situation?

It seems to me that your equipment requires a surge in startup current that exceeds the output of your batteries. Parallel supercaps could remedy this, or a higher current output battery bank (i.e. adding more batteries in parallel). IMHO