Published: 9 August 2013
Category: Q&A
Raymond asks this question, which concerns a project to install inverters to control electric motors, and their isolation needs. It has been answered by SELECT (Theme – Electrical Control):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: I’m currently involved in a project to install inverters to control electric motors and I need to know the requirements for isolation of the motors.
The installation involves inverters at ground level to control motors at high level (approximately 4m above the ground). I shall be fitting isolators and emergency stops at the motors but I am unsure as to whether I need to fit isolators at the inverters, given that the distribution board supplying the inverters will be within 3m of the units.
Please advise of layout required for this installation to comply with BS7671.
Answer: For the requirements to isolate from invertor to motor for safety reasons, refer to BS 7671:2008 (2011) 537.2.2.2, 537.2.2.5 and 537.3.1.
As for the distribution board being within 3m, depending on the overcurrent and fault protection requirements, isolate all live supply conductors that may cause shutdown problems for all the final circuits relating to the distribution board.
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