Avoiding voltage losses in long cables
01 October 2008
One of the difficulties faced by designers of automation systems is the inherent voltage drop associated with long cables. How do you ensure that the voltage at the point of use is at the specified level? DIN rail power supply specialist, Puls, believes it has the answer.
The biggest problem with voltage drops is that they are current dependent, so calculating them can be tricky, especially when the load is variable as is the case in a motor or robotic system. The current method is to adjust the voltage above what is required, and hope that it will be correct at the load connection. This is not good practice and under certain conditions an excessive voltage may be applied to equipment, leading to damage.
Puls’ CD range of compact DIN rail mounting dc/dc converters, used in conjunction with the company’s XT range of semi-regulated bulk power supplies, is an economical solution to the voltage drop problems experienced in large automation systems. This approach provides a large, semi-regulated ac/dc power supply for the total power requirement, with the smaller CD modules installed closer to the loads, be they motors, robots or other control devices.
The CD units are currently available in four different models, with input voltages of 18Vdc to 34Vdc and 36Vdc to 60Vdc, and output voltage options of 12-15Vdc or 23-28Vdc. The power available per individual unit is 96W for the 12-15Vdc version and 120W for the 23-28Vdc versions. Puls UK managing director, Harry Moore recalls a particular application that benefited greatly from this dual configuration.
“We were approached by a conveyor manufacturer who was having big issues with voltage drops causing motor stalls and operational failures. My mind instantly turned to our new dc/dc units as a possible solution to the manufacturer’s problem. Their small size and robust physical and electrical design and construction suited our customer’s needs down to the ground. The switch to our high-efficiency XT units also enabled them to create a more efficient and lower cost system.”
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