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NVR switch help please.

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NVR switch help please.

Postby Mike G » 20 Mar 2016, 21:25

I wonder if someone could help me with adjusting the switch on my pillar drill? The drill will only run for maybe 15 minutes before it cuts out, and will then cut out every 2 or 3 minutes, which is all rather inconvenient when you are running batches of work through it. This is what it looks like:

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I presume that adjustment is by turning the black plastic knob on the top in the last couple of photos, but I have no idea which way or how much. Any advice gratefully received.
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Re: NVR switch help please.

Postby kirkpoore1 » 21 Mar 2016, 05:10

Mike, it looks like there is a pointer on there set to about 2.4 amps. Does the pointer or scale move when you turn the knob? Failing that, you could give it a couple of turns and see if the motor runs longer or shorter.
What's the amp rating on the motor? Have you tried to measure the draw while its under load to see if the overload is set correctly?

I figure any motor that might be overloading that frequently ought to be asked to explain itself. :)

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Re: NVR switch help please.

Postby 9fingers » 21 Mar 2016, 10:34

Mike,
There are two possibilities and without test equipment difficult to prove what the fault is.

1) the motor is drawing excess current due to a fault and the thermal overload is doing its job in protecting it from further damage.

or
2) the thermal overload has become ultra sensitive through age and it tripping at a much lower current than it is set for ( 2.4amps as Kirk says)


Just after one of these trip episodes, is the motor hot to the touch, a little off cold or as cold as the nearby metalwork of the drill?

Provided the motor is not hot, then I would suggest turning the knob on the overload - usually clockwise for higher setting and you should see the scale move. Adjust it up to just over the 2.5 amp mark and see if things improve.
Look on the motor plate to see what the current draw should be. Normally the overload would be set at that figure or perhaps 10% up on that.
Try and avoid the temptation to turn it up all the way without first understanding what is happening. This is a protection device after all and setting too high could cost you a new motor as the windings become the weakest link.

If it turns out that the trip is weak/defective then spares are not likely to be available - contact your local ark breakers yard :lol:
A replacement NVR would be needed £30 at Toolsatan but quite a bit bigger and uglier than your current one.

If the motor is running hot after 15mins work, then that needs to be investigated and repaired/replaced.

More than happy to give continued support- please report back.

Bob
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Re: NVR switch help please.

Postby Mike G » 21 Mar 2016, 14:58

Thanks Kirk, Bob.

The motor plate is entirely blank. It is a piece of brass, which may have been polished excessively, but there is absolutely nothing on it whatever. This tool may have been renovated, as there are splashes of paint where there shouldn't be, including on the motor plate. I'll leave the drill running now and report back on the motor temperature, and how long it took to trip.
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Re: NVR switch help please.

Postby kirkpoore1 » 21 Mar 2016, 15:45

Mike G wrote:Thanks Kirk, Bob.

The motor plate is entirely blank. It is a piece of brass, which may have been polished excessively, but there is absolutely nothing on it whatever. This tool may have been renovated, as there are splashes of paint where there shouldn't be, including on the motor plate. I'll leave the drill running now and report back on the motor temperature, and how long it took to trip.


Mike, if you have an amp meter I would also get some reading with it, both unloaded and while you're drilling. Unless the motor is a much-to-small replacement (which you would notice via a lack of power), or has issues like Bob said, I can't believe it's going to overheat.

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Re: NVR switch help please.

Postby Mike G » 21 Mar 2016, 16:46

Right, I left the drill running, unloaded (ie I didn't use it) and it switched itself off after 27 minutes. The motor casing was gently warm, certainly not hot, but certainly warmer than the casing of the drill.
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Re: NVR switch help please.

Postby kirkpoore1 » 21 Mar 2016, 16:53

I think your motor is OK. Time to turn up the allowed current on the switch.

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Re: NVR switch help please.

Postby 9fingers » 21 Mar 2016, 17:07

kirkpoore1 wrote:I think your motor is OK. Time to turn up the allowed current on the switch.

Kirk



100% agree

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Re: NVR switch help please.

Postby Mike G » 21 Mar 2016, 19:26

OK, thanks guys. I'll give it a try tomorrow. Best to do this at roughly 1/10 amp at a time until it doesn't cut out under continuous running?
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Re: NVR switch help please.

Postby 9fingers » 21 Mar 2016, 20:05

Mike G wrote:OK, thanks guys. I'll give it a try tomorrow. Best to do this at roughly 1/10 amp at a time until it doesn't cut out under continuous running?


I'd go up 10-15% -say 2.8 and assuming that is OK, bring it down a little and then keep an eye on it as you do your various jobs. That algorithm should get you there with minimal watching and waiting.

Bob
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Re: NVR switch help please.

Postby kirkpoore1 » 21 Mar 2016, 20:18

9fingers wrote:
Mike G wrote:OK, thanks guys. I'll give it a try tomorrow. Best to do this at roughly 1/10 amp at a time until it doesn't cut out under continuous running?


I'd go up 10-15% -say 2.8 and assuming that is OK, bring it down a little and then keep an eye on it as you do your various jobs. That algorithm should get you there with minimal watching and waiting.

Bob


Bob, would it be worthwhile to guess and go the FLA rating of typically sized motors? I know that here in the US motors almost always fall into one of a few sizes, and their amp ratings within those sizes usually fall in a pretty close range. For example, I checked two Leesons and one Baldor 1/2 hp motors, and they used 4.4, 4.4, and 4.2 amps @ 240v 1ph. But I don't know what size motors typically equip that kind of machine there.

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Re: NVR switch help please.

Postby 9fingers » 21 Mar 2016, 20:50

kirkpoore1 wrote:
9fingers wrote:
Mike G wrote:OK, thanks guys. I'll give it a try tomorrow. Best to do this at roughly 1/10 amp at a time until it doesn't cut out under continuous running?


I'd go up 10-15% -say 2.8 and assuming that is OK, bring it down a little and then keep an eye on it as you do your various jobs. That algorithm should get you there with minimal watching and waiting.

Bob


Bob, would it be worthwhile to guess and go the FLA rating of typically sized motors? I know that here in the US motors almost always fall into one of a few sizes, and their amp ratings within those sizes usually fall in a pretty close range. For example, I checked two Leesons and one Baldor 1/2 hp motors, and they used 4.4, 4.4, and 4.2 amps @ 240v 1ph. But I don't know what size motors typically equip that kind of machine there.

Kirk


Kirk, those currents sound very high by UK standards. I've just looked up a 1/2hp 240v and the FLC is 2.73 amps.
I'd expect the drill to have originally been fitted with about 1/2hp. We don't know what is on there now. Such an industrial looking machine would have been 3 phase at one time and converted to single phase by a previous owner.

The only example I have to hand here is a 1/3 hp 110v 4.7amps
So that is 517va for 1/3hp or 1550va per hp. That makes a 1/2 hp 775va or 3.2 amps at 240v
All a bit hand wavy but a degree of consistency and perhaps supporting that Mike's drill is set a bit low for 1/2hp.

Bob
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Re: NVR switch help please.

Postby kirkpoore1 » 21 Mar 2016, 21:34

Bob, I went and looked at a few more ads with 1/2hp 1725 rpm motors, and got full load amp ratings of 3.2, 3.5, and 3.8 amps. So the spread is certainly wide enough to make my method impractical, I guess. Ah, well, it was a thought.

If we assume this is a replacement motor, maybe what the previous owner did was put a half horse motor in place of a third horse motor, but he didn't know that he also had to increase the setting on the starter. Since that's also a 1ph switch, I would think it would have been properly sized if the 1ph motor had replaced a 3ph motor.

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