IEC60034 - How do you prove motor duty? 2

[Etrix]

Hello all,

I've come up against a lifeboat manufacturer who doesn't appear to have in-house expertise enough to tell me more about the motor they have installed. It started out simply enough: original motor offered was 37kW S1 (continuous duty according to IEC60034). Our increased lifting load requirements then caused them to increase motor rating to 56kW S2 10 min (non-continuous duty, IEC60034). Accepted the use of this motor, expecting them be able to demonstrate, with a test cert from their motor manufacturer/supplier, that this motor was indeed 56 kW S2 10 min.

1) Is my request for cert showing 56kW S2 10 min unreasonable? (I ask because we've been back and forth on the issue for months and am beginning to wonder about the validity of my request)

2) They now want to test the motor - can somebody point me to a relevant section in the IEC60034 (or indeed any other European/IEC standard) which shows how you prove a 56kW S2 10 min rated motor is indeed what it says on the tin?

Thanks everyone - not much motor experience, please be patient with me, I might return the favour one day when you ask about something else.

Regards,
Etrix (Electrical)

 

[jbartos]

Suggestion: The motor has to be designed for such a duty, and comply with IEC60034. Has the motor manufacturer tech support been contacted?

 

[gsimson]

As per the thumb rule followed the rating at S1 duty is equivalent to S2 - 60 min rating. 56 kW at S2 - 10 min will be less than 37 kW S1 duty. Other than real short term duty 56 kW S2 duty - 10 min motor may not work.
Simplest test is to conduct load test at your site at full load current with min starting kick. However the motor can be restarted only & only when the temperature of the winding comes down to ambient.

 

[UKpete]

Etrix, from the information you have supplied:

1) your request for a test at 56kW for 10mins - I think it is reasonable as you have some doubts about their experience with motors (can they be sure it will meet the S2 10mins rating which in your case is approx 50% above the S1 rating). I can understand their reluctance, they will have to pay for a test either by the motor manufacturer or by a suitable organization (possibly not a motor rewinder, being able to perform an accurate short-term load test requires the right equipment and experience, many of them just do a light run after repairing a motor).

2) it is IEC60034-1 that defines the duties, this may also define the test requirements (at least it should refer you to the relevant part of IEC60034). I can tell you what they are though
(ref. DG Searle "European Electric Motors", Roles Publishing *):

The test requires that at the beginning of the test the motor temperatures should be within 5°C of the coolant temperature (the ambient air temperature for your typical TEFC motor), and after the test the maximum temperature rise should not exceed that normally specified for duty type S1 (the continuous rating), e.g. for a class H motor, 125°C rise (as defined in IEC 60034-1).

S2 is a short time duty i.e. it covers running at a constant load for a time less than that to reach thermal equilibrium followed by a period at rest (de-energized) of sufficient duration to re-establish the motor within 2°C of the coolant temperature (as implied by gsimson). Are you confident this applies to your application i.e. the off period will probably have to be something like a minimum of 2 hours?

Regarding the likelihood of the motor being able to pass this test - I am uneasy about the rule of thumb stated previously, it must depend on the size of the motor, that is its thermal inertia. For what it's worth, I think your motor will be physically large enough to pass the test. You can probably have a stab at calculating it, given it's mass and efficiency.

* this book is packed with motor information, it is for the motor user rather than designer. It is also very expensive; borrow it if you can!

 

[UKpete]

Etrix, I have checked my standards at work and I can confirm that it is IEC60034-1 that applies. This is a 75-page spec. and describes all the tests and test methods, as well as the duty types.

 

[Etrix]

Thanks jbartos, gsimson and UKpete for your responses.

UKpete, I have looked up 60034-1 before I put this question down, but I needed a nod in the right direction. Thanks for your invaluable post, and after another hard look at IEC 34-1, I have demanded for a re-test at its alternative S2 rating.

IEC60034-1 clause 4.8 states that machines with more than one rating "shall comply with this standard in all respects at each rating" - I know this is fundamental and should not even be questioned, but the people I deal with have to be seen/heard to be believed.

Once again, thanks.