Topics

Motor starting jolt

Oren
 

I finally got my 9b on line, new felts and belts all set. Part of the process included a new Leeson 1hp capacitor start motor, which I was really looking forward to. But, the damn thing starts with such a jolt that it almost seems dangerous for the lathe, or at the least, disruptive to doing close tolerance work. 

I’m thinking I must need a smaller start capacitor, but I don’t see much discussion of this on the internet. Most info is about increasing capacitor size...


Any ideas? Should I try to mount the motor in a non standard way in order to isolate it?

Any advice will be greatly appreciated. 

Gregg Eshelman
 

Look up a soft starter or slow starter. Might find one surplus or used for less than new $


On Saturday, December 23, 2017, 1:20:00 PM MST, obolt@... [SOUTHBENDLATHE] wrote:



I finally got my 9b on line, new felts and belts all set. Part of the process included a new Leeson 1hp capacitor start motor, which I was really looking forward to. But, the damn thing starts with such a jolt that it almost seems dangerous for the lathe, or at the least, disruptive to doing close tolerance work. 

I’m thinking I must need a smaller start capacitor, but I don’t see much discussion of this on the internet. Most info is about increasing capacitor size...


Any ideas? Should I try to mount the motor in a non standard way in order to isolate it?

Any advice will be greatly appreciated.

Nelson Collar
 

A lower compositor will soften the start but you might wear them out quicker. 

On Saturday, December 23, 2017, 3:19:34 PM EST, obolt@... [SOUTHBENDLATHE] wrote:


 

I finally got my 9b on line, new felts and belts all set. Part of the process included a new Leeson 1hp capacitor start motor, which I was really looking forward to. But, the damn thing starts with such a jolt that it almost seems dangerous for the lathe, or at the least, disruptive to doing close tolerance work. 

I’m thinking I must need a smaller start capacitor, but I don’t see much discussion of this on the internet. Most info is about increasing capacitor size...


Any ideas? Should I try to mount the motor in a non standard way in order to isolate it?

Any advice will be greatly appreciated. 

Rick Rick
 

Check for any looseness that may be causing the jolt.  Like pulley looseness on the shafts.  I once repaired a lathe that started too slow, I identified the motor as a dual voltage motor that was wired for 220V and plugged into 110V.  It it possible yours is the reverse of that?  A motor wired for 110V and provided with 220V?  Something seems amiss as this is not a usual complaint.

Oren
 

Thanks for the replies thus far. I’m beginning to wonder if it’s possible that I miswired the motor...it’s wired for 110 by me and I presumed I did it correctly and it’s definitely supplied with 110 as I wired the shop myself. Is it possible to miswire it and create a large startup jolt then have everything run fine after startup? When I first tested it unloaded on the bench after wiring it it jumped badly...I assumed that was because it had no load...now I’m wondering.

Stephen Bartlett
 

Even worse is having one connection set for 120 volts and the other for 240. Instant motor death.

I once worked for GE in Lynn, Mass. We had several different voltages available, in the same locations.

We moved a simple, single phase IBM card sorting machine from one side of a room, on a 208 volt receptacle, and tied it to a 240 volt source on the other side of the room.

The motor immediately burned out.

It turned out that the motor's internal connections had been set up for 120 volt operation. The 208 volt source was actually down to about 200 volts and the motor was fine for years. Once it was hit with 240 it was gone.

Steve Bartlett

SOUTHBENDLATHE@... wrote:


Posted by: "Oren" obolt@...com
Date: Sun Dec 24, 2017 8:41 am ((PST))

Thanks for the replies thus far. I’m beginning to wonder if it’s possible that I miswired the motor...it’s wired for 110 by me and I presumed I did it correctly and it’s definitely supplied with 110 as I wired the shop myself. Is it possible to miswire it and create a large startup jolt then have everything run fine after startup? When I first tested it unloaded on the bench after wiring it it jumped badly...I assumed that was because it had no load...now I’m wondering.

Oren
 

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.

Stephen Bartlett
 

Another thought: Make sure there is no lost motion in the drive train -- all pulleys tight on their shafts, belt(s) properly tensioned, etc.

Anything that would let the motor get turning before the spindle starts to turn.

Steve Bartlett

SOUTHBENDLATHE@... wrote:


Posted by: "Oren" obolt@....com
Date: Sun Dec 24, 2017 4:01 pm ((PST))

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.

Gregg Eshelman
 

Motor soft starters. There's a YouTube video for that.



On Sunday, December 24, 2017, 7:03:45 PM MST, Stephen Bartlett tower.op@... [SOUTHBENDLATHE] wrote:


Another thought:  Make sure there is no lost motion in the drive train
-- all pulleys tight on their shafts, belt(s) properly tensioned, etc.

Anything that would let the motor get turning before the spindle starts
to turn.

Steve Bartlett

>
>    Posted by: "Oren" obolt@....com
>    Date: Sun Dec 24, 2017 4:01 pm ((PST))
>
> I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.

Nfwood
 

Why not put a VFD on a 220 VAC motor and program it for slow start?

Nelson Wood


-----Original Message-----
From: Oren obolt@... [SOUTHBENDLATHE]
To: SOUTHBENDLATHE
Sent: Sun, Dec 24, 2017 7:01 pm
Subject: Re: [SOUTHBENDLATHE] Motor starting jolt

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.




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John Griffin
 

Induction motors designed to deliver big starting torque (eg, compressor duty) can give a jolt when hooked up to something like a table saw or a lathe

eg, "The 1 HP LEESON Compressor Duty Electric Motor is a dependable and powerful single-phase motor designed especially for compressors requiring high breakdown torque and rugged mechanical construction. UL listed. CSA certified." 

LEESON Compressor Duty Electric Motor — 1 HP, 115/230V, 3600 RPM, Model# 110160



The issue is high inrush current. If you wired in a particularly stiff (high current) 115 VAC circuit in your shop, this will amplify the issue. One remedy is to wire from the outlet to the motor using a wire size and length calculated by the motor full load running current (on motor tag). This will dampen start up jolt.

The above motor is FL rated at about 13A. Just for grins, splice in a 25' - 50' roll of 14 AWG between 115 VAC outlet and motor then test. This approach would be a lot cheaper than a solid state soft start

On Sun, Dec 24, 2017 at 7:01 PM, Oren obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.



Ray De Jong
 

The motor has 2 (two) things wrong in my estimation #1 - it is a quick start motor as in last reply.
Worst of all though #2 - it is too high speed for your lathe, it should be a 1725 (nominal).
South Bend lathes were only supplied with the lower speed motors and would only be useable at 3450rpm if a further speed reduction was used; as with the "as supplied pulley arrangement" a 3600 rpm motor will run the spindle at too high speed for the headstock bearings (sleeves) and would be too high speed for machining most metals unless run in back gear.
I could be wrong about this but I have operated and have owned a number of SB's from 9" to 16" and have not yet encountered a higher than 1725rpm motor except on one 14" inch line-driven SB that we converted to 4spd. automotive transmission and we used an 1140rpm motor on a 2:1 reduction from the motor to jackshaft then from the transmission output shaft onto the middle pair of flat belt pulleys
hopefully this will help
cheers
ray

On Monday, December 25, 2017, 9:58:03 AM PST, John M Griffin griffinjohnm@... [SOUTHBENDLATHE] wrote:


 

Induction motors designed to deliver big starting torque (eg, compressor duty) can give a jolt when hooked up to something like a table saw or a lathe

eg, "The 1 HP LEESON Compressor Duty Electric Motor is a dependable and powerful single-phase motor designed especially for compressors requiring high breakdown torque and rugged mechanical construction. UL listed. CSA certified." 

LEESON Compressor Duty Electric Motor — 1 HP, 115/230V, 3600 RPM, Model# 110160



The issue is high inrush current. If you wired in a particularly stiff (high current) 115 VAC circuit in your shop, this will amplify the issue. One remedy is to wire from the outlet to the motor using a wire size and length calculated by the motor full load running current (on motor tag). This will dampen start up jolt.

The above motor is FL rated at about 13A. Just for grins, splice in a 25' - 50' roll of 14 AWG between 115 VAC outlet and motor then test. This approach would be a lot cheaper than a solid state soft start

On Sun, Dec 24, 2017 at 7:01 PM, Oren obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.



eddie.draper@btinternet.com
 

Dear all,

Different motors have different starting characteristics, and this applies to both single & 3 phase.  If you take a 1 ph motor intended for rapid starting on load, and a compressor which might be on load is a simple example, it is likely to have a starting winding which is designed both to have and to live with a high current, as provided by a high value C.

Reducing the number of Farads in the C or putting a resistor in series with the whole thing will prolong start up quite satisfactorily.  Meanwhile, the running winding is being subject to excessive current for longer than it otherwise would be.  It may be designed to cope with that, it may not, particularly when installed on a lathe which requires frequent starts as you aproach finished dimensions and want to take frequent measurements.  I would strongly recomend contacting the motor manufacturer for their recomendation, as without knowing what they designed into it, making changes that alter the starting characteristics in this application might best be described as "brave".

Eddie



From: "John M Griffin griffinjohnm@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Monday, 25 December 2017, 17:58
Subject: Re: [SOUTHBENDLATHE] Motor starting jolt

 
Induction motors designed to deliver big starting torque (eg, compressor duty) can give a jolt when hooked up to something like a table saw or a lathe

eg, "The 1 HP LEESON Compressor Duty Electric Motor is a dependable and powerful single-phase motor designed especially for compressors requiring high breakdown torque and rugged mechanical construction. UL listed. CSA certified." 

LEESON Compressor Duty Electric Motor — 1 HP, 115/230V, 3600 RPM, Model# 110160



The issue is high inrush current. If you wired in a particularly stiff (high current) 115 VAC circuit in your shop, this will amplify the issue. One remedy is to wire from the outlet to the motor using a wire size and length calculated by the motor full load running current (on motor tag). This will dampen start up jolt.

The above motor is FL rated at about 13A. Just for grins, splice in a 25' - 50' roll of 14 AWG between 115 VAC outlet and motor then test. This approach would be a lot cheaper than a solid state soft start

On Sun, Dec 24, 2017 at 7:01 PM, Oren obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 
I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.





Guenther Paul
 

If a jolt means a electrical shock at startup , i would check the grounding of the electrical supply and system   RPM have no play in it
 
GP



From: "Ray De Jong dejongray@... [SOUTHBENDLATHE]"
To: "John M Griffin griffinjohnm@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...>
Sent: Monday, December 25, 2017 1:40 PM
Subject: Re: [SOUTHBENDLATHE] Motor starting jolt

 
The motor has 2 (two) things wrong in my estimation #1 - it is a quick start motor as in last reply.
Worst of all though #2 - it is too high speed for your lathe, it should be a 1725 (nominal).
South Bend lathes were only supplied with the lower speed motors and would only be useable at 3450rpm if a further speed reduction was used; as with the "as supplied pulley arrangement" a 3600 rpm motor will run the spindle at too high speed for the headstock bearings (sleeves) and would be too high speed for machining most metals unless run in back gear.
I could be wrong about this but I have operated and have owned a number of SB's from 9" to 16" and have not yet encountered a higher than 1725rpm motor except on one 14" inch line-driven SB that we converted to 4spd. automotive transmission and we used an 1140rpm motor on a 2:1 reduction from the motor to jackshaft then from the transmission output shaft onto the middle pair of flat belt pulleys
hopefully this will help
cheers
ray

On Monday, December 25, 2017, 9:58:03 AM PST, John M Griffin griffinjohnm@... [SOUTHBENDLATHE] wrote:


 
Induction motors designed to deliver big starting torque (eg, compressor duty) can give a jolt when hooked up to something like a table saw or a lathe

eg, "The 1 HP LEESON Compressor Duty Electric Motor is a dependable and powerful single-phase motor designed especially for compressors requiring high breakdown torque and rugged mechanical construction. UL listed. CSA certified." 

LEESON Compressor Duty Electric Motor — 1 HP, 115/230V, 3600 RPM, Model# 110160



The issue is high inrush current. If you wired in a particularly stiff (high current) 115 VAC circuit in your shop, this will amplify the issue. One remedy is to wire from the outlet to the motor using a wire size and length calculated by the motor full load running current (on motor tag). This will dampen start up jolt.

The above motor is FL rated at about 13A. Just for grins, splice in a 25' - 50' roll of 14 AWG between 115 VAC outlet and motor then test. This approach would be a lot cheaper than a solid state soft start

On Sun, Dec 24, 2017 at 7:01 PM, Oren obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 
I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.





Oren
 

Thanks all, for your help. It has been really useful. I didn’t really focus on the motor design characteristics...the model number led me astray and sounded perfect for the application. When I used the catalog number instead for Leeson 110088.00 it showed it to be a farm duty HIGH TORQUE motor, designed for heavy use including compressors. So, at least I now have a clear definition of the problem thanks to your input.

It is a wonderful 1hp 1725 rpm 110 v motor wired correctly and running on a well wired 110 v circuit, but apparently a bad choice for the application. “Jolt” was meant to describe a sharp mechanical jump at startup, not an electrical shock.

I don’t mind reducing the start capacitor or the circuit wire size even if it shortens the life of the motor as I have no other use for it other than my Benchmaster mill where it would be even more of a poor fit.
So, any suggestions on how to tame it are still welcome. I plan on reducing the startup capacitor size tomorrow as a first step.

Jim_B
 

Be careful about REDUCING the capacitance.

The starting circuit is a series RLC circuit.

The REACTANCE of a capacitor INCREASES as the capacitance go’s down.

X= 1/(2*pi*f*C)

It also cares a negative sign.

So Z= R+ X(l)-X(c) Where Z is the total reactance of the starting circuit.

 

This, smaller capacitator, COULD increase the starting current.

It depends on which side of resonance you are.   Resonance is when (X(l)=X(c))

 

If the manufacturer could save money by supplying a smaller capacitator without effecting reliability I think they would.

 

The starting circuit provides a local phase that is phase shifted from the house phase. This creates a rotating field that starts the motor. Without it, the local phase,  the roter would rotate to the nearest stator field and lock there.

The ideal situation for maximum torque would be when X(l)=X(c). This would produce 90 degrees of shift.   At this point the current through the starting field would be maximum. Due to manufacturing variations  and cost considerations this may or may not be your case.  

 

I would try paralleling another capacitor with clip leads to see if it helped. Bigger C means less reactance and a starting field with less phase shift so, perhaps, less starting torque.

Of course going to a small cap will eventually result in a large capacitive reactance which will have a similar effect. A very small cap would resemble an open circuited capacitator  in the starting circuit.

A very large capacitator would resemble a shorted capacitator in the starting circuit.

 

 

Jim B.

 


Virus-free. www.avast.com

Steven Schlegel
 

Would it be best to add resistance to the starting windings or in series with the capacitor? Based on the math, that wouldn't affect the phase, it would decrease the current in the starting winding, and is dirt cheap.

I'm way out of my league here, so please, everyone, provide some comments on what I just said.

Steven

On Dec 25, 2017 1:16 PM, "'Jim B. ' Jim@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...> wrote:
 

Be careful about REDUCING the capacitance.

The starting circuit is a series RLC circuit.

The REACTANCE of a capacitor INCREASES as the capacitance go’s down.

X= 1/(2*pi*f*C)

It also cares a negative sign.

So Z= R+ X(l)-X(c) Where Z is the total reactance of the starting circuit.

 

This, smaller capacitator, COULD increase the starting current.

It depends on which side of resonance you are.   Resonance is when (X(l)=X(c))

 

If the manufacturer could save money by supplying a smaller capacitator without effecting reliability I think they would.

 

The starting circuit provides a local phase that is phase shifted from the house phase. This creates a rotating field that starts the motor. Without it, the local phase,  the roter would rotate to the nearest stator field and lock there.

The ideal situation for maximum torque would be when X(l)=X(c). This would produce 90 degrees of shift.   At this point the current through the starting field would be maximum.. Due to manufacturing variations  and cost considerations this may or may not be your case.  

 

I would try paralleling another capacitor with clip leads to see if it helped. Bigger C means less reactance and a starting field with less phase shift so, perhaps, less starting torque.

Of course going to a small cap will eventually result in a large capacitive reactance which will have a similar effect. A very small cap would resemble an open circuited capacitator  in the starting circuit.

A very large capacitator would resemble a shorted capacitator in the starting circuit.

 

 

Jim B.

 


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Jim_B
 

Here is a solution.

https://www.ebay.com/itm/Baldor-S22CA-2-3HP-115-230V-SS-STARTER/262926324282?hash=item3d37a1523a:g:Q2UAAOSwfVpYp2qx

He is asking for more than a surplus motor/VFD combination would cost but he is open for bids and I bet he has a  very limited customer base.

You can read about this item here.

 

 

There is also this one. I don’t know more about it than what’s on the ad. Perhaps the seller could advise.

https://www.ebay.com/itm/USED-NORDIC-SERIES-25B-DUAL-RAMP-SOFT-START-INDUCTION-MOTOR-CONTROLLER/132264562543?hash=item1ecb950f6f:g:WGEAAOSwo4pYUY4o

 

 

 

Looking at the internet,  They seem to say put a resistor in the run winding and then take it out with a relay when running.

A 1 HP motor should draw about 7.5 amps when running. Starting is more say 10 to 15  Amps.  

 

Question.

Do you have, or can you borrow a 10A Veriac. A  Veriac is an adjustable Auto Transformer.

 

You would want to drop the voltage, perhaps to ½.  A Veriac here would tell you how low.

That would be about a 60  Volt drop and at 15 Amps starting 4 ohms would do.

Now you have a power issue.

 

Power is I^2*R For 15 amps and 4 ohms that 900 watts. True its not continuous but it’s a lot until you get the motor running and out of the start mode.

 Just to be safe I would think you need a 100 or 200 watt resistor.

 

While I was typing this I had an Idea. Just for a test.

I measured the toaster in the kitchen. It was 2 Ohms.

Also about 1000 watts.

Try wiring a toaster in series with your motor. I MEAN CLIP-LEADS NOT CUT THE COARD.

See if that does anything.

 

Just thinking, can you get your hands  a substantial silicon diode.

This will reduce the AVERAGE voltage by ½ without dissipating any power.

You would need about 400 V at 20 or 30 amps.

If you can beg/borrow one try it in series with one power leg.

 

Apparently the soft start boxes use an SCR.  Sort of like a diode that can be turned on within 1 cycle of the AC.

They give better  and variable soft start control. With a series diode only your motor will be full on for  8.3 ms and off for 8.3 ms etc. That just might be enough to slow it down

 

 

Jim B.

 

From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...]
Sent: Monday, December 25, 2017 5:31 PM
To: SOUTHBENDLATHE@...
Subject: RE: [SOUTHBENDLATHE] Motor starting jolt

 

 

Would it be best to add resistance to the starting windings or in series with the capacitor? Based on the math, that wouldn't affect the phase, it would decrease the current in the starting winding, and is dirt cheap.

 

I'm way out of my league here, so please, everyone, provide some comments on what I just said.

 

Steven

 

On Dec 25, 2017 1:16 PM, "'Jim B. ' Jim@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...> wrote:

 

Be careful about REDUCING the capacitance.

The starting circuit is a series RLC circuit.

The REACTANCE of a capacitor INCREASES as the capacitance go’s down.

X= 1/(2*pi*f*C)

It also cares a negative sign.

So Z= R+ X(l)-X(c) Where Z is the total reactance of the starting circuit.

 

This, smaller capacitator, COULD increase the starting current.

It depends on which side of resonance you are.   Resonance is when (X(l)=X(c))

 

If the manufacturer could save money by supplying a smaller capacitator without effecting reliability I think they would.

 

The starting circuit provides a local phase that is phase shifted from the house phase. This creates a rotating field that starts the motor. Without it, the local phase,  the roter would rotate to the nearest stator field and lock there.

The ideal situation for maximum torque would be when X(l)=X(c). This would produce 90 degrees of shift.   At this point the current through the starting field would be maximum.. Due to manufacturing variations  and cost considerations this may or may not be your case.  

 

I would try paralleling another capacitor with clip leads to see if it helped. Bigger C means less reactance and a starting field with less phase shift so, perhaps, less starting torque.

Of course going to a small cap will eventually result in a large capacitive reactance which will have a similar effect. A very small cap would resemble an open circuited capacitator  in the starting circuit.

A very large capacitator would resemble a shorted capacitator in the starting circuit.

 

 

Jim B.

 

 

Virus-free. www.avast.com

 


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Jim_B
 

BE VERY VERY CAREFUL WITH THE CLIP LEADS

Don’t need a 911 on Christmas

 

 

Jim B.

 


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Gary Johnson
 

The Leeson 110088.00 is a capacitor start, capacitor run motor. http://www.leeson.com/TechnicalInformation/sphase.html  The two caps are in parallel when starting, then the centrifugal switch disconnects the much larger starting cap. Such motors can produce more starting toque than a plain capacitor start motor. They also offer higher efficiency and lower power factor since the run capacitor roughly cancels the inductive reactance i.e., it is approximately resonant. 

It is NOT resonant during startup. The start capcitor provides nearly all the required phase shift, thus a very large value is needed, somewhere around 10X the run cap.

Starting torque will decrease with smaller starting capacitor values, but of course you must avoid a stall condition under any expected starting load. You could experiment by substituting other values, or placing them in SERIES with the start capacitor to create an effectivley lower value  Ctotal = C1*C2/(C1+C2). Never alter the value of the RUN capacitor. Another factoid: Without the start capacitor, the system becomes a Permanent Split Capacitor motor, which still has storting torque, but not very much. So you could give it a try with no start capacitor at all (with no load, pelase).

Limiting the inrush current will also reduce starting torque. So the suggested experiment with a long skinny extension cord is actually a nice simple test to see how it behaves. 

The soft starter like Jim recommended is a good solution. (If I was starting from scratch, I'd go with a DC permag motor and variable speed, like I did for my mill.)

-Gary

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