4 replies to this topic

[GGOSS]

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

[GGOSS]

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

regards,
GGOSS

[schow]

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

Cheers!

[GGOSS]

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

[schow]

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;