Phase rotation advice

P

Phil

-
Hello all,
I'm after some advice on my current situation as I've never came across this before and trying to find answers online are not producing any results.

Basically I've got a 3 Phase motor, checked voltages across the 3 lines and neutral, everything is as it should be.

Checked rotation, L1 to L2 ok, L2 to L3 is not showing rotation but it's showing 400V, L3 to L1 is ok.

Why would L2 to L3 not show rotation but will show 400V?

Thank you for any advice.
 
Sort by date Sort by votes
Phil said:
Hello all,
I'm after some advice on my current situation as I've never came across this before and trying to find answers online are not producing any results.

Basically I've got a 3 Phase motor, checked voltages across the 3 lines and neutral, everything is as it should be.

Checked rotation, L1 to L2 ok, L2 to L3 is not showing rotation but it's showing 400V, L3 to L1 is ok.

Why would L2 to L3 not show rotation but will show 400V?

Thank you for any advice.
Click to expand...
What test equipment are you using?
 
Upvote 0 Downvote
Just to add to my original post, I've load tested the genset with a 3 Phase heater whilst out on site, again everything was at it should.

The reason for the questions is because someone has hired one of our generators for a hoist, last night the generator was shutting down for reverse power. I've came to site, checked everything over with the generator, checked the wiring up to the hoist and now waiting for their hoist engineer to turn up.

Edit: just seen your reply. It's a ethos 4164 phase rotation tester.
 
Upvote 0 Downvote
Phil said:
Hello all,
I'm after some advice on my current situation as I've never came across this before and trying to find answers online are not producing any results.

Basically I've got a 3 Phase motor, checked voltages across the 3 lines and neutral, everything is as it should be.

Checked rotation, L1 to L2 ok, L2 to L3 is not showing rotation but it's showing 400V, L3 to L1 is ok.

Why would L2 to L3 not show rotation but will show 400V?

Thank you for any advice.
Click to expand...
Why would you have TP& N at the three phase motor? I take it the motor is a bog standard Squirrel cage type machine, nothing special about it?
 
Upvote 0 Downvote
telectrix said:
don't quite understand your question. to check rotation, you connect all 3 lines to the rotation meter. then it shows the direction of the phase rotation, clockwise or anti-clockwise.
Click to expand...
Sorry, it probably the way I worded my post.

I know how to check phase rotation but when I check between L2 and L3 no indication is shown for the direction of rotation, yet 400V is shown. When I check between L1 and L2, correct rotation is shown and between L3 and L1 correct rotation is shown.

Yes Pete, it's a squirrel cage type machine.
 
Upvote 0 Downvote
clear now, having watched the video that pete posted. i've never checked rotation using his 2nd method.
 
Upvote 0 Downvote
Pete999 said:
You need a new tester Phil.
Click to expand...
Do you think everything is as it should be? I can get a new tester when I get back to the depot today or tomorrow.
I'm just really confused why it doesn't show up L2 to L3 but does L3 to L1.
I'm just trying to rule everything out before the hoist engineer turns up starts blaming the generator.
 
Upvote 0 Downvote
Does it always show no rotation L2 to L3? Does it always show correct rotation between other phases? If so that would suggest there is something different about that measurement, but probably worth checking with a second meter.

If you use the probes the other way round do you get Phase rotation (the opposite way)?

When you added the load from the heater did you still get 400v between all phases?
 
Upvote 0 Downvote
If you are doing what Pete's video shows and you are only seeing rotation in 2 phases, then doesn't that mean you only looking at 2 phases? Test method, test instrument or labelling wrong perhaps?
 
Upvote 0 Downvote
Pete999 said:
You need a new tester Phil.
Click to expand...
I could be barking up the wrong tree, your tester Phil does not have the L1 L2 markings, although there there are L/R sequence lamps, as I say maybe completely wrong, but are you sure the tester show is capable of doing Phase Sequence testing? It's just a thought. Could it be as someone has already said, your test method is wrong?
 
Upvote 0 Downvote
How good is the earth reference for the generator? Those two wire rotation tests rely on the source being properly earthed as they take an earth reference via capacitive coupling to the hand of the operator.

I think you'd be better off testing phase rotation with a proper phase rotation tester or mft with this function.

You said the generator is shutting down on reverse power, is it running in parallel with other generators?
Reverse power on a generator normally means that power is feeding in to this generator from another connected generator or other source.
 
Upvote 0 Downvote
davesparks said:
How good is the earth reference for the generator? Those two wire rotation tests rely on the source being properly earthed as they take an earth reference via capacitive coupling to the hand of the operator.

I think you'd be better off testing phase rotation with a proper phase rotation tester or mft with this function.

You said the generator is shutting down on reverse power, is it running in parallel with other generators?
Reverse power on a generator normally means that power is feeding in to this generator from another connected generator or other source.
Click to expand...
Backfeeding, of course, wondered what the OP meant with reverse power.
 
Upvote 0 Downvote
If the generator runs the hoist in one direction but not the other I suspect the problem lays not with generator but the hoist. The reverse direction may be placing more load on the generator and it is locking out/shutting down.
 
Upvote 0 Downvote
If there is no other load on the genny but the hoist, then when the hoist lowers it might well regenerate into the genny and trip it with reverse power. Motors can regenerate into the grid as it has a near infinite capacity to absorb reverse power (think solar!) but a standalone genny can't absorb much power without risk of its AVR losing control, hence its panel is configured to detect this and trip the supply. It might be set too sensitive, but if reverse power is genuinely the problem, adding some load in parallel will solve it.

Agree with Davesparks - 2-wire rotation testers are a fudge - the voltage between any two lines does not have rotation but it detects the relative phasing by capacitive coupling to the outside world like a voltstick. If the supply is not properly earth-referenced (e.g. N-E link is open) or the user is in close proximity with something elevated from earth, then the indication can be misleading. I don't use or trust them, only 3-wire rotation testers can give an authoritative answer.
 
Upvote 0 Downvote
Thank you all for your replies, I'm sorry I have not been back on the forum to reply, as soon as I finished that job I was up to Aberdeen to sort another break down.

Just to clear things up, my company just supplied the generator, another company sized the generator and done the wiring to the hoist.

When the hoist engineer turned up we were able to start testing, massive voltage drops when operating the hoist and as someone mentioned previously the hoist was causing the reverse power.

Phoned the company that done the wiring for them to get 16mm cable and they argued they sized the cable correctly and then asked if we can not just turn the voltage up on the generator??? Anyways event got them to replace the cable and hey presto, it's all sorted.

The company does have a proper all singing tester but that stays in the depot so only had my personal tester with me.

I thank you all again for your answers and for your time!
 
Upvote 0 Downvote
Phil said:
Thank you all for your replies, I'm sorry I have not been back on the forum to reply, as soon as I finished that job I was up to Aberdeen to sort another break down.

Just to clear things up, my company just supplied the generator, another company sized the generator and done the wiring to the hoist.

When the hoist engineer turned up we were able to start testing, massive voltage drops when operating the hoist and as someone mentioned previously the hoist was causing the reverse power.

Phoned the company that done the wiring for them to get 16mm cable and they argued they sized the cable correctly and then asked if we can not just turn the voltage up on the generator??? Anyways event got them to replace the cable and hey presto, it's all sorted.

The company does have a proper all singing tester but that stays in the depot so only had my personal tester with me.

I thank you all again for your answers and for your time!
Click to expand...
Tester is not much good stuck in the main Depot, when all the problems that need testing are out on site, ofr is the tester someones special purchase?
 
Upvote 0 Downvote
Pete999 said:
Tester is not much good stuck in the main Depot, when all the problems that need testing are out on site, ofr is the tester someones special purchase?
Click to expand...

I take the tester with me when I'm going to electrical break downs from the depot, in this case I went straight from another job, but I can't keep it in the van as we need it to RCD test the generators before they go out on hire.

It's only a small company, the only just started spending money on the electrical side of things since I started last year.

My own collection of tools and testers is small compared to what most you guys will have. I've been in the army for the last 13 years and all tools etc was provided, I'm slowly buying my own stuff, already spent 100s since starting with this company.
 
Upvote 0 Downvote
Phil said:
I take the tester with me when I'm going to electrical break downs from the depot, in this case I went straight from another job, but I can't keep it in the van as we need it to RCD test the generators before they go out on hire.

It's only a small company, the only just started spending money on the electrical side of things since I started last year.

My own collection of tools and testers is small compared to what most you guys will have. I've been in the army for the last 13 years and all tools etc was provided, I'm slowly buying my own stuff, already spent 100s since starting with this company.
Click to expand...
All my tools were provided Phil so I know how you feel
 
Upvote 0 Downvote

Similar threads

A
How to ensure correct phase rotation on generator
Replies
5
Views
329
Rockingit
Rockingit
S
3 phase EV Charger on 2 phases.
Replies
8
Views
551
sheppertonspark
S

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Green 2 Go Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses Heating 2 Go
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Advert

YOUR Unread Posts

Daily, weekly or monthly email

Receive a daily, weekly, or monthly email containing a digest of new and recently updated threads.

Thread starter

P

Phil

-
Joined
Location
Scotland

Thread Information

Title
Phase rotation advice
Prefix
N/A
Forum
UK Electrical Forum
Start date
Last reply date
Replies
37
Unsolved
--

Thread Tags

Tags Tags
advice phase rotation

Advert

Thread statistics

Created
Phil,
Last reply from
Pete999,
Replies
37
Views
5,688

Advert

TrueNAS JBOD Storage Server

Tilers | UK Tiling Forum | Tilers Forums | Find a Tiler
Plumbers Forums | Plumbing Advice | Gas Forum
Back
Top