Industrial Floor Sander not getting enough current?

[Mark Hughes]

I have an at my local scout group. They have employed a company to sand & varnish their hall floor. the company is using a couple of Lagler Hummel machines 230v 50Hz each requiring a 16A supply. (as a screenshot).

A 16A fused socket has been connected to the hut ring main (by replacing a faceplate) to bypass the need for a 13A plug. This was tried but obviously, the startup current blew the 13A fuse.
With both of the machines, they start but the bag refuses to inflate (only one machine tried at a time). The company suggested this was a supply issue..

A separate 16A socket supply was then configured from the consumer unit, from a different phase, using what would have been the cooker circuit but the issue persisted.

The scout group then borrowed a 5KVA generator and again the problem exists. Post the generator test you would assume that the issue was with the machine.. but there are 2 of them identical.

Anyone any thoughts or seen this behaviour before and can provide any pointers?
The company is adamant is not their machines - they were fine on their last job a couple of days ago!

 

[Lucien Nunes]

It seems unlikely that the supply is at fault. If the voltage drop is large enough to seriously impair the machine performance at around 16A load (typical for a 2.2kW motor) you would likely have noticed it with other equipment too. Can you connect a voltmeter to the same circuit as the machine and check the voltage off-load and on-load? From a purely functional point of view, if the on-load voltage is within tolerance, the supply is OK. Do you know anything about how the supply gets to the hut, e.g. does it have its own supply from the public network or is it piggybacked off another building via miles of cable zigzagging around fields?

I would be cautious about reading too much into the test with the generator. Most small gens don't like large induction motor loads as the power factor affects the voltage regulation, resulting in a need to significantly oversize the gen to get reliable performance.

 

[James]

It might help if you could post a video of the machine starting and running.

 

[telectrix]

my money would be on volt drop. premises maybe long run supply as Lucien mentioned.

 

[James]

I am wondering if the machine is never getting up to a high enough speed to change from the start capacitor to the run capacitor. That would leave the machine underpowered.

with things like this it is often necessary to start them with no load, I.e. not in contact with the floor until they have got up to full speed.

 

[Mark Hughes]

They called me after the issue was recognized but not physically seen it but:

• The supply is 3-phase.
• The cooker circuit is <5 meters from the 3-phase board.
• The voltage drop measured seems quite large drops from 248 to 238 under load; they had no method of measuring current.

Interestingly enough the hall is heated using bar heaters, admittedly split across the phases, but these were still working fine yesterday.

I am wondering if the machine is never getting up to a high enough speed to change from the start capacitor to the run capacitor. That would leave the machine underpowered.

with things like this it is often necessary to start them with no load, I.e. not in contact with the floor until they have got up to full speed.

Correct; looks like the machine has a built-in soft start, don't know that for sure. The motor seems to run but the bag doesn't inflate.

 

[Mark Hughes]

It seems unlikely that the supply is at fault. If the voltage drop is large enough to seriously impair the machine performance at around 16A load (typical for a 2.2kW motor) you would likely have noticed it with other equipment too. Can you connect a voltmeter to the same circuit as the machine and check the voltage off-load and on-load? From a purely functional point of view, if the on-load voltage is within tolerance, the supply is OK. Do you know anything about how the supply gets to the hut, e.g. does it have its own supply from the public network or is it piggybacked off another building via miles of cable zigzagging around fields?

I would be cautious about reading too much into the test with the generator. Most small gens don't like large induction motor loads as the power factor affects the voltage regulation, resulting in a need to significantly oversize the gen to get reliable performance.

The generator idea was one suggested by the firm; sounds like they'd used this method before. The supply is its own 3-phase and the hall has a single 3-phase board that everything is fed from, but not sure how far from the sub. The Hall does still have wall-mounted electric heaters, split across the phases and both these and the electric oven appeared to be working OK. As a means to try and test the supply.

 

[westward10]

The heaters will appear to function as they are resistive and have no motion unless they are fan heaters. A drop of 25v from the cooker being in use is high.

 

[Mark Hughes]

The heaters will appear to function as they are resistive and have no motion unless they are fan heaters. A drop of 25v from the cooker being in use is high.

OK thx; to confirm heaters aren't fan heaters but resistive.

We plumbed the machine into the cooker circuit to do a parrallel test with the same results as the main hall ring circuit - so yes would agree its a Voltage drop issue. NB: I updated the text after I rechecked what it was (248 dropped to 238 so enough of a drop but not 25V as I earlier alluded to.)

We reconnected the cooker circuit and that worked but again that is primarily a resistive circuit as an element with a 'small' fan.

Worth speaking to the DNO?

 

[Rockingit]

Makes no sense, frankly. You're seeing a volt drop on start-up that's still 8v HIGHER than nominal. Also - do the maths - you're losing 10v at only a maximum of 16A?? That's a massive resistance. Also, you've not said anything about circuit overload protection kicking in which suggests that the issue isn't current.

Without wishing to sound condescending, are you sure the machines don't have some sort of transport locking pin still in place that's simply not allowing them to spin?

 

[Lucien Nunes]

But 238V is spot on, so regardless of whether the supply resistance is high, the machines should work fine. Where was that voktage messured? I would start getting interested if it fell below 220V but would still expect it to work. The supply can be +/-10% and 11.5V drop is allowed in the circuit.

 

[James]

If this is a hire machine, can you request the company that provided it comes and helps you by demonstrating the correct way to use it?

 

[Matt Collins]

If this is a hire machine, can you request the company that provided it comes and helps you by demonstrating the correct way to use it?

No, it's not a hire machine. They are contractors doing the work.

 

[Matt Collins]

Makes no sense, frankly. You're seeing a volt drop on start-up that's still 8v HIGHER than nominal. Also - do the maths - you're losing 10v at only a maximum of 16A?? That's a massive resistance. Also, you've not said anything about circuit overload protection kicking in which suggests that the issue isn't current.

Without wishing to sound condescending, are you sure the machines don't have some sort of transport locking pin still in place that's simply not allowing them to spin?

I did ask them this and they have said that there isn't any other switches or locks on the machine.

 

[James]

No, it's not a hire machine. They are contractors doing the work.

I think they need to get a service engineer out to diagnose and repair it.
it is entirely possible that even though it worked at the last job, it has been damaged or become defective during transit.

loose connection, damaged or corroded pins in the plug, there are other possible faults but it really needs someone with the skills and equipment to diagnose it correctly.

 

[Mark Hughes]

Makes no sense, frankly. You're seeing a volt drop on start-up that's still 8v HIGHER than nominal. Also - do the maths - you're losing 10v at only a maximum of 16A?? That's a massive resistance. Also, you've not said anything about circuit overload protection kicking in which suggests that the issue isn't current.

Without wishing to sound condescending, are you sure the machines don't have some sort of transport locking pin still in place that's simply not allowing them to spin?

I've asked questions around the machines but nothing obvious or sensible from the operators that imply they are doing anything out of the ordinary. I see no logical reason but two machines not working.. Got to be something quite simple either machines or a fault. Not sure if a N fault on the supply side would manifest itself like this given the issue is consistent across phases; I've try and get down to check Ze & Zs but if it's a fault I can't see why it can be anything other than DNO side.

 

[James]

I have come across things like this before where seemingly identical faults appear on 2 different machines.
sometimes it’s a common extension lead or a trailing socket has damaged the plugs on both machines etc.

if you have provided a socket that is showing 220v or higher when under load, the fault is between the point of measurement and the sanding disk.
again, it needs a person on site that knows how to test systematically

 

[Rockingit]

I've asked questions around the machines but nothing obvious or sensible from the operators that imply they are doing anything out of the ordinary. I see no logical reason but two machines not working.. Got to be something quite simple either machines or a fault. Not sure if a N fault on the supply side would manifest itself like this given the issue is consistent across phases; I've try and get down to check Ze & Zs but if it's a fault I can't see why it can be anything other than DNO side.

Z tests will tell you nothing (except possibly a loose connection in a neutral, which may explain the Vd) and you'll still have two dead machines. You are definitely missing a piece of the jigsaw here and in danger of over-thinking things.

 

[Mark Hughes]

I have come across things like this before where seemingly identical faults appear on 2 different machines.
sometimes it’s a common extension lead or a trailing socket has damaged the plugs on both machines etc.

if you have provided a socket that is showing 220v or higher when under load, the fault is between the point of measurement and the sanding disk.
again, it needs a person on site that knows how to test systematically

James thanks; Agreed I need to be there to see for myself. The downside is the contractor is looking to walk away from the job.

 

[Lucien Nunes]

Ze and Zs aren't hugely relevant because the integrity of the earthing doesn't make any difference to whether the machines work. It's Zp-n that you want to know. A high resistance on the neutral serious enough to stop the machines working would probably cause other effects with lights and appliances interacting and possibly failing, because when one P-N voltage goes down, the others go up. A localised high resistance e.g. bad connection, as opposed to an excessively long thin circuit, would tend to overheat under load.

Could you please explicitly confirm that the 238V mentioned in post #6 is measured L-N on the circuit with the machine operating?

Post crossed with various others saying the same thing. Must type faster.