Preventing interference of electrical noise in emergency operations

Power generation equipment producer Cummins has changed the control system inside its generators to prevent the electrical noise from adversely impacting on the operation of hydraulic generators in emergency vehicles.

The company explains that many pieces of apparatus used by emergency personnel, such as battery chargers, variable-speed evacuation fans or lighting, depend on a mobile generator to supply 110 V alternating current power.

Each of these pieces of equipment will work when plugged into a traditional wall socket connected to the electricity grid and most will also work as designed when connected to a mobile generator, even when multiple units are being powered at the same time.

However, as the power supplies in these devices are nonlinear – often with a variable electrical draw – electrical noise, such as power factor issues, waveform distortion and additional zero crossing, can be introduced on the line. These may cause compatibility issues that reduce effectiveness or even potentially damage the auxiliary devices or other equipment on vehicles. While each device may work well on its own, when placed in sequence, unforeseen problems can occur, explains the company.

With the modification of the control system inside Cummins’ generators to prevent the electrical noise from adversely impacting on the operation of generators, the company no longer references the line voltage to get its frequency regulation signal. Instead, Cummins uses a toothed wheel with a magnetic pickup, which has resolved nearly all complaints concerning generators not running properly when powering specific devices.

Cummins notes that, even with the generator operating properly, electrical noise can cause problems with other devices plugged into the system. Thus, the company highlights that it is very important that any new emergency apparatus connected to a generator is fully tested with all the powered devices on the vehicles.

Ideally, devices should be added one by one – especially nonlinear loads such as variable-frequency drive fans, light-emitting diode lights or uninterrupted power systems – to verify the amount of power being drawn for proper operation. The goal is to simulate as many real-life scenarios as possible, explains the company, in order to pre-empt and prevent failures.

Cummins notes that this is especially relevant when transferring auxiliary devices from an apparatus being retired to a new apparatus. Just because a device worked with older equipment is no guarantee that it will work with new equipment, the company stresses. Testing undertaken by Cummins further shows that each specific device needs to be tested in its application, and not just verified by the manufacturer model number. “Fully evaluating all electrical components as they will be used on the scene of the emergency will provide peace of mind,” says the company.