Addition of Motors in HT Panel.

These are the things you need to check for the adding the new motors:

(1) Verify the bus capacity is enough

(2) Verify the incoming breaker and disconnetor capacity is enough

(3) Verify the incoming cable capacity is enough in terms of ampacity and voltage drop

(4) Verify all other upstream systems (transformer, cable, disconnector, breakers, generators etc., - starting from the MCC to the final power source) capacity is enough

(5) If there is an existing motor larger than the new motors connected to the MCC, you don't need to worry about the starting current, otherwise verify the voltage dip caused by the starting current of the largest new motor

(6) It may need additional section to add to the MCC, verify there is enough space (including working space) available

(7) Addition of new section needs MCC shutdown, so communicate with the production department for the required down time

(8) If the motor are controlled and monitored by DCS, verify the DCS system has enough capacity to handle the additional motors

(9) Verify the cable tray capacity. You may need to install additional cable trays

(10)Consider updating all the related drawings and documents due to the additional motors

(11)Verify the relay coordination study and it may require to change upstream breaker or relay settings

(12)If the new motors are big enough compared to the existing motor, it is also required to do the short circuit calculation (large size motor also contribute short circuit currents to the system) and verify the short circuit capacity of the MCC bus

If you use any electrical system study software (like ETAP and SKM) and the system is already modeled in the software, it will be easy to verify most of the items with running load flow study, motor acceleration study, device coordination study and short circuit study.

When an electrical system is designed it is always good practice to have some provision to add new loads in future and I believe your system also designed with same practice and it may have enough capacity to add additional motors but it must be verified by a qualified engineer. However, it all depends on how much load will be added compared to the existing loads.

- MS