Hi All,

As it has been a long time since my last post or response, I thought I might ask a couple of questions that may generate some interest and on-going discussion. These relate to starter ratings presentied in the format described by IEC60947-4-2.

Consider the following example.

125A: AC53a: 3.5 - 10: 70 - 10

125A implies starter rating expressed in Amps

AC53a implies starter is suitable for driving a squirrel cage motor and that the amps rating is based on continuous (non-bypassed) operation.

3.5 - 10 implies a maximum starting current of 3.5 x starter amps for a period not exceeding 10 seconds.

70 - 10 implies an on-load factor of 70% and 10 starts per hour equally spaced.

My questions are as follows:

1. Assuming we are able to start the driven machine within 5 seconds at a starting current not exceeding 3.5 time the starter rating, can we achieve 20 starts per hour (equally spaced and at 70% on-load factor) without compromising starter service life?

2. An on load factor of 70% and 10 starts per hour equally spaced implies a period of 350 seconds between completion of 1 start (ramp) and commencement of the next. What is the affect on starter ratings if the soft stop function is enabled?

I look forward to your responses.

Regards,
GGOSS

Still looking for help on this one. Can anyone provide some clues?

regards,
GGOSS

Please can anyone tell me what are the requirements (sub-clauses) of IEC60947-4-2? How many items are they?

Cheers!

Hello Schow,

Breakdown of IEC 60947-4-2 is as follows;

IEC 60947 is the standard applicable to Low-voltage Switchgear & Controlgear.

Part 4 of that standard relates to contactors and motor-starters.

Section 2 relates to AC Semiconductor motor controllers and starters.

Hope this helps.

Regards,
GGOSS

Hi GGOSS,

Thanks for the info but I need details of all sub-clauses, eg. for AC Drive EMC test IEC-61800-3, there are a few tests such as ESD, THD, conducted and radiated immunity, surge etc....If I remember correctly, there are about 7 or 8 tests altogether but for IEC/EN60947-4-2, how many are there?

I tried to check from our local test lab and most of them do not know details about this test. Pls can you tell me what are they? I need to look for a lab who can conduct tests required for IEC/EN60947-4-2.

Cheers! ;c;