"will run, but is underperforming" needs clarification

Do we mean is very slow to start, or even after many mins never gets up to speed?

(and I assume they do not mean it is turning backwards - if that is true then swap any 2 phases...)

and is the 415V still true while the motor is under-performing or was that the 'off load' reading.

It might be interesting to look at the three phase to ground voltages - while on load-  too.

A high impedance supply may lead to a no-start or a very slow one but once at speed it should be OK. Unless backwards of course...

Mike

Have a look at the stated inrush current and compare it to the tripping curve of the breaker.  Worth looking at the cable calculation and volt drop as well from source of instalation as this may go through Db1 then DB2 then DB3

Thanks Mike. It's running way below the pressure it should - meaning it's running slow (although I've not measured the RPM - but the only way a fan can generate less pressure than it should is by running slow).

It's not running backwards - we even ran it backwards just to sanity check and things are the same!

I don't think we have phase to ground voltages on load - that is worth a check.

mapj1 said:

A high impedance supply may lead to a no-start or a very slow one but once at speed it should be OK. Unless backwards of course...

That was my thinking! I can't come up with a reason for a slow run...

That is also worth a look. It's close to the local DB but could be quite a way from the main DB and if that is not on a decent cable size...

And do not overlook the obvious mechanical factors-  at the other location where it works is the mounting different (gravity the same way up, frame twisted by un-even supports, ducting sizes - does it have a duct ?)

Mike.

yep 100% the same. No duct, all in one unit - even built the same room around it just in case!

Hmm how odd.

Let us know what the voltage tests find.  And if you can find a clamp meter, does it draw the same current on all 3 phases.

M.

Yep will do. Will put the clamp on as well...

Are the motor windings correctly connected ? If each winding is designed for 230/240 volts they should be connected in star.

If each winding is intended for 400/415 volts they should be connected in delta.

230 volt windings are popular in Europe as they may be used from in delta from 3 phase 230 volt supplies. 400 volt windings are popular for applications with a 400/690 volt supply as they be used in star from 690 volts.

If 400/415 volt windings are connected in star to a standard UK supply and therefore only receive 230/240 volts, the motor will run sort of but with reduced performance.

The excessive inrush current can induce a voltage sag in the supply circuit, which can impair the performance of the motor. Power factor correction can help reduce the current demand, installed locally at the motor to minimize the reactive power. What is the cross-sectional area of the circuit conductors? Also, does the DOL starter have a motor brake relay ?