Star delta issue (driving me insane)

[GSGFaw]

Heeelp!

I have an 11kW/21A motor which is attached to a hydraulic power pack.

I have replaced the old panels with new, using the same star delta starting. When connected to a 415V outlet protected by a C32 breaker, the breaker will periodically trip. This has only manifested since the new panels, but the new control circuit is just a basic star delta (open transition). The only difference is the motor connection on the panel is now pluggable (to allow for quick changeover in the event of a failure).

I've tried "rolling" the connections in the motor (as suggested by an old hand elsewhere) to no effect.

The pump has to be started onload for operational reasons (doesn't trip offload) and this is when the MCB trips; for info, the old starters do not trip the external breaker.

I've checked starting currents using my fluke in max/min and, on average, get around 24A at both the star and delta phases of startup (at the panel's MCCB) and then the running load is 10.7A. When the C32 breaker trips, there is no current spike captures on my Fluke.

If I switch to a D32 fed socket, the issue goes away (obviously), but my guys can't be guaranteed they will have a D type breaker on the site sockets provided.

Anyone dealt with this or have a suggestion as to what I can do to fix the issue? I've wired many star deltas over the decades and never experienced this issue.

p.s. Softstarting not an option as the guys have to inch the motor frequently, and the starts per hour don't even remotely suit one.

 

[LeeH]

Have you done basic motor testing? IR? Are the windings balanced?

Are the terminations secure in the plug and socket?

You won’t see a current spike on a clamp on, the sampling time will be too large at a guess.

 

[davesparks]

Is the star delta timer set correctly?

 

[Fazz711]

Most motor where I work are covered by D type can you swap for one of them to try ?

 

[DPG]

Most motor where I work are covered by D type can you swap for one of them to try ?

He says he's tried one and it's fine.

 

[pc1966]

For an 11kW star-delta motor Hager recommends a 50A C-curve, or 32A D-curve MCB (or BS88 fuse).

 

[pc1966]

When the C32 breaker trips, there is no current spike captures on my Fluke.

What Fluke mode is that? I have found clamp meters with "max hold" often don't record short spikes, and you only need a few ms of enough current to trip the magnetic side of a MCB.

 

[GSGFaw]

Have you done basic motor testing? IR? Are the windings balanced?

Are the terminations secure in the plug and socket?

You won’t see a current spike on a clamp on, the sampling time will be too large at a guess.

Yeah, motor winding nicely balanced and insulation checks out fine.

Is the star delta timer set correctly?

I've tried multiple combos (2 to 10 second transition) and delays (20ms to 140ms) and basically get the same result each time. The star to delta delay setting definitely improves the issue slightly on some settings but the problem remains

Most motor where I work are covered by D type can you swap for one of them to try ?

Yes, I have said the same to my work but, and it is frustrating, it comes back to "why don't the old star delta panels trip?"

 

[GSGFaw]

For an 11kW star-delta motor Hager recommends a 50A C-curve, or 32A D-curve MCB (or BS88 fuse).

Can you provide a link to this data?

 

[pc1966]

Can you provide a link to this data?

If you get the commercial distribution catalogue from here:

Hager Brochures, Catalogues & Documentations | Hager UK

Discover all the product documentation you need in our brochures & catalogues! Download what you need in one click straight from Hager Official website!

hager.com

The details are on page 112 for section "Transformers & Motors Protection". The 'NCN' column is their C-curve MCB, the NDN the D-curve.

 

[GSGFaw]

If you get the commercial distribution catalogue from here:

Hager Brochures, Catalogues & Documentations | Hager UK

Discover all the product documentation you need in our brochures & catalogues! Download what you need in one click straight from Hager Official website!

hager.com

The details are on page 112 for section "Transformers & Motors Protection". The 'NCN' column is their C-curve MCB, the NDN the D-curve.

While that doesn't explain why the old starters don't trip the C type, it at least gives me supporting evidence that a C type 32A isn't a reliable supply option.
All the HPUs have been fully refurbished and so COULD be a little "tight" for a while (pure speculation, but makes sense)

 

[davesparks]

Yes, I have said the same to my work but, and it is frustrating, it comes back to "why don't the old star delta panels trip?"

Was the old panel protected by the same MCB?

 

[mainline]

What Fluke mode is that? I have found clamp meters with "max hold" often don't record short spikes, and you only need a few ms of enough current to trip the magnetic side of a MCB.

He needs one of these bad boys.

https://www.farnell.com/datasheets/1965966.pdf

 

[Petej999]

Most motor where I work are covered by D type can you swap for one of them to try ?

Agree surprised at some of the replies though

 

[DPG]

Agree surprised at some of the replies though

In his original post he mentions D types.