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7/29/2013 1:09 PM  
Joined: 7/29/2013 Last visit: 7/23/2018 Posts: 5 Rating: (0) 
Hi all! I have a project. that is STS crane system for port. My system are 4 motor group. Main Hoist, Trolley, Gantry and Boom.My partner chose transformer for the system. and i have to check. I think some problem. + In crane systemMain motor type choice is continuous S1. But in mechanic calculation the duty is S3. In STS crane, the hoist motor frequently have to increase / decrease speed and braking. I think, when we calculate, we have to calculate is P_{2}=P_{RMS}*1.4. + i don'tknow what the calculations were correct or not? Please help me! Caculation file in attachment thanks!
Attachmentcaculation trans.pdf (69 Downloads) 
Last edited by: O_Moderator at: 7/29/2013 8:22 PM 

7/30/2013 5:51 AM  
Joined: 1/5/2009 Last visit: 4/24/2019 Posts: 261 Rating: (45) 
Hi. Lets us understand the difference b/w S3 and S4 Duty Cycle first. S3: This refers to operation which consists of a number of identical laod cycles, each comprising a period under constant load and internal. The starting current doesnt have a significant effect on the heat rise. In practise, intermittent periodic duty is a series of onload and offload periods in Figure A attached. A number of onload periods of varying lengths between them are repeated cyclically. The Cyclic duration factor for the whole duty cycle is derived from the equation: CDF= ∑ tb* 100( in %)/ (∑ tb + ∑ tst) In terms of DIN VDE, the preferred values of cyclic duration factor are 25%. S4: This refers to operation comprising a sequence of identical duty cycles each consisting of a significant runup tim, a time at constant load and an interval. In practise the CDF in percent, the number of starts per hour and the power ratings e.g. 40%. and hence for S4 duty your power calculation seems right. 
8/4/2013 5:40 PM  
Joined: 7/29/2013 Last visit: 7/23/2018 Posts: 5 Rating: (0) 
Thanks M Valli! But S3 or S4 duty is not main problem! My main problem is " Main Transformer capacity calculation" . The main transformer power in caculate is 630KVA. In my crane system, i don't known this result is correct or not?
