SCCR FOR CONTROL PANEL WITH SERVO DRIVES

[tom@tsl]

I have a customer that is wanting an sccr rating of 45ka. The issue is the Yaskawa drives lowering the rating to 35ka. Speaking with Yaskawa, I can use a different fuse that would bring this to 42ka.

Question, other than an isolation transformer, how can I raise the overll SCCR rating? Can I put a branch disconnect in front of the drive fuses??? Would this circuit now be rated at the kva of the disconnect???

Feeder Circuit​	​	​	​
E7LRL36600U31X​	SQ D BREAKER 600V 600A 100KA SCCR​	100KA​	​
Control Transformer ​	​	​	​
E5LPCC15​	BUSSMANN FUSE CLASS CC 15 AMP​	200kA​	​
E5811-421​	WAGO FUSE HOLDER CLASS CC 2P​	100kA​	​
E363322308​	SOLA TRANSFORMER REG 3KVA 600V 60HZ​	1200A​	​
General Transformer ​	​	​	​
E5LPCC30​	BUSSMANN FUSE CLASS CC 30 AMP​	200kA​	​
E5811-421​	WAGO FUSE HOLDER CLASS CC 2P​	100kA​	​
E3HS10F7.5AS​	SOLA TRANSFORMER 7.5KVA 600V 60HZ​	3970A​	​
Chain Rail Temp​	​	​	​
E5LPCC20​	BUSSMANN FUSE CLASS CC 20 AMP​	200kA​	4600A​
E5811-431​	WAGO FUSE HOLDER CLASS CC 3P​	100kA​	​
E920403​	HUBBELLOCK RECEPT 30A,600V​	10kA​	​
E921415B​	HUBBELLOCK M PLUG 30A,600V​	10kA​	​
Vacuum Pump​	​	​	​
E5LPCC20​	BUSSMANN FUSE CLASS CC 20 AMP​	200kA​	4600A​
E5811-431​	WAGO FUSE HOLDER CLASS CC 3P​	100kA​	​
E920403​	HUBBELLOCK RECEPT 30A,600V​	10kA​	​
E921415B​	HUBBELLOCK M PLUG 30A,600V​	10kA​	​
Heat Tunnel​	​	​	​
E5LPCC10​	BUSSMANN FUSE CLASS CC 10 AMP​	200kA​	​
E5LPCC20​	BUSSMANN FUSE CLASS CC 20 AMP​	200kA​	​
E5LPCC30​	BUSSMANN FUSE CLASS CC 30 AMP​	200kA​	​
E5811-411​	WAGO FUSE HOLDER CLASS CC 1P​	200kA​	​
E5811-421​	WAGO FUSE HOLDER CLASS CC 2P​	100kA​	​
E7SOI885070​	CELDUC SSR 600V 50A, CURRENT SENSE​	100kA​	​
E92010-1201​	WAGO 2C TRM GRY 20-6 AWG 51A​	100kA​	​
E92004-1201​	WAGO 2C TRM GRY 20-6 AWG 51A​	100kA​	​
E92002-2201​	WAGO 2C DBL-STK GRY 22-12 AWG 20A​	100kA​	​
E92006-1201​	WAGO 2C TRM GRY 20-10 AWG 30A​	100kA​	​
Top Platen Drive*​	​	​	​
E5LPJ50SP​	BUSSMANN FUSE CLASS J 50 AMP​	300kA→35kA​	4300A​
E5CH60J3I​	BUSSMANN FUSE HOLDER CLASS J 3P​	200kA​	​
E3SGDV-370D01A​	YASKAWA S5 DRIVE 400V 15KW​	5kA​	​
Bottom Platen Drive*​	​	​	​
E5LPJ50SP​	BUSSMANN FUSE CLASS J 50 AMP​	300kA→35kA​	4300A​
E5CH60J3I​	BUSSMANN FUSE HOLDER CLASS J 3P​	200kA​	​
E3SGDV-370D01A​	YASKAWA S5 DRIVE 400V 15KW​	5kA​	​
Index Drive*​	​	​	​
E5LPJ50SP​	BUSSMANN FUSE CLASS J 50 AMP​	300kA→35kA​	4300A​
E5CH60J3I​	BUSSMANN FUSE HOLDER CLASS J 3P​	200kA​	​
E3SGDV-370D01A​	YASKAWA S5 DRIVE 400V 15KW​	5kA​	​
Plug Drive*​	​	​	​
E5LPJ50SP​	BUSSMANN FUSE CLASS J 50 AMP​	300kA→35kA​	4300A​
E5CH60J3I​	BUSSMANN FUSE HOLDER CLASS J 3P​	200kA​	​
E3SGDV-370D01A​	YASKAWA S5 DRIVE 400V 15KW​	5kA​	​
​	​	​	​

 

[Jraef]

Can I put a branch disconnect in front of the drive fuses??? Would this circuit now be rated at the kva of the disconnect???

No, you cannot, unless you want to fork over around $25k for some destructive series testing at a high powered lab and have about 6 months to get that scheduled... (and hope it passes).

If, with the new fuses, Yaskawa is telling you that the highest SCCR for the servo drives is 42kA, then nothing you can do will allow you to put a higher SCCR on that panel. You have only 3 options as I see it:

1. to implore upon Yaskawa to test it higher with maybe a different fuse,
2. change servo drives to one that can be series listed at 45kA or more, or
3. implore upon your customer to lower their Available Fault Current (AFC) to 42kA or less.

The "isolation transformer" does NOT change the SCCR of the panel, but it lowers the AFC of the source circuit (which goes to the last point above).

Side note for future reference: You don't have to list the transformers and plugs/receptacles, UL does not count those in the calculations...

 

[petersonra]

At 42 K you are pretty close. It would not take a whole lot of extra wire to lower the AFC from 45 to 42.

 

[Elect117]

What is the max AFC at the switchgear? (The SCCR rating of the main)

How long is the run projected to be?

 

[tom@tsl]

No, you cannot, unless you want to fork over around $25k for some destructive series testing at a high powered lab and have about 6 months to get that scheduled... (and hope it passes).

If, with the new fuses, Yaskawa is telling you that the highest SCCR for the servo drives is 42kA, then nothing you can do will allow you to put a higher SCCR on that panel. You have only 3 options as I see it:

1. to implore upon Yaskawa to test it higher with maybe a different fuse,
2. change servo drives to one that can be series listed at 45kA or more, or
3. implore upon your customer to lower their Available Fault Current (AFC) to 42kA or less.

The "isolation transformer" does NOT change the SCCR of the panel, but it lowers the AFC of the source circuit (which goes to the last point above).

Side note for future reference: You don't have to list the transformers and plugs/receptacles, UL does not count those in the calculations...

Thank you for a fast and detailed resposne

 

[Jraef]

At 42 K you are pretty close. It would not take a whole lot of extra wire to lower the AFC from 45 to 42.

Can't say I haven't done that...

 

[Jraef]

What is the max AFC at the switchgear? (The SCCR rating of the main)

How long is the run projected to be?

Good point. A lot of "don't know all the details" engineering projects will use ASS-u-me-d data, such as "infinite bus" fault current values for the primary of the utility transformer, or fail to account for cable distances, which may affect that ACTUAL values of the AFC. When you are this close, it pays to challenge the data (a little). I have had utility reps give me an AFC value, only to find out later that they themselves used "infinite bus" for their primary. In that case, I too was at them telling me that they had 44kA AFC at my MCC terminals, I had gear rated for 42kA. After the challenge, a more senior EE at the utility ran the real numbers, turned out they actually only had 37kA...