Aircraft Hoover test

[graeme210375]

I have the opportunity to test the equipment for an aircraft cleaning company. This will include the test of 5 x 115v / 400Hz class 2 vacuum cleaners. The vacuums have 30 metre leads with special 3 pin plugs attached. How can I test using this voltage and frequency? The company also owns a towable 500litre potable water cart with an in built immersion element. This is fed via a 16 amp plug. Would this be an item that requires testing? Which tests would I perform?

 

[grantr37]

I don't know, are the planes not excluded as they come from different countries all over the world and are only in the UK for a short duration.......400Hz?? is that what the aircraft electrical system works on?

 

[graeme210375]

I don't know, are the planes not excluded as they come from different countries all over the world and are only in the UK for a short duration.......400Hz?? is that what the aircraft electrical system works on?

The aircraft that the company clean tend to be UK based as they are cleaned at night when they have finished their sectors. The cleaning company are a UK company so are still governed by HASAWA and Electricity at work acts. 400Hz is the standard frequency used on the aircraft. There is no way of changing the frequency on my tester. I may just have to perform a visual inspection on the vacuum cleaners. Still not sure about the water cart though.

 

[Marnik]

250V I/R test

 

[Patman]

BEWARE !!

Aircraft electrical components operate on many different voltages both AC and DC. However, most of the aircraft systems use 115 volts (V) AC at 400 hertz (Hz) or 28 volts DC. 26 volts AC is also used in some aircraft for lighting purposes. DC power is generally provided by “self-exciting” generators containing electromagnetics, where the power is generated by a commutator which regulates the output voltage of 28 volts DC. AC power, normally at a phase voltage of 115 V, is generated by an alternator, generally in a three-phase system and at a frequency of 400 Hz. Higher than usual frequencies, such as 400 Hz, offer several advantages over 50 Hz – notably in allowing smaller, lighter power supplies to be used for military hardware, commercial aircraft operations and computer applications. As aircraft space is at a premium and weight is critical to aircraft engine thrust and fuel burn (and thus the aircraft range and engine horsepower per pound), 115 volts at 400 Hz offers a distinct advantage and is much better than the usual 50 Hz used in utility power generation. However, higher frequencies are also more sensitive to voltage drop problems. There are two types of drops: resistive and reactive. Resistive losses are a function of current flowing through a conductor with respect to the length and size of the conductor. This is the most important factor in controlling resistive power loss and applies regardless of frequency. The short transmission range of higher frequencies is not a factor in most airborne applications. Reactive drops, on the other hand, are caused by the inductive properties of the conductor. Reactive drops are a function of both cable length and the AC frequency flowing through the conductor. With high frequencies such as 400 Hz, reactive drops are up to seven times greater at 50 Hz.This raises an interesting question: can you run a 400 Hz device at 50 Hz.? If you try this, smoke and fire are certain to result. The lower winding inductance draws a much higher current at a set voltage, saturates the iron, and burns up. However, there is a simple workaround using fundamental principles of flux density. A 400 Hz device will usually run just fine on 60 Hz if you lower the voltage to 50/400ths or 0.125. The same current will produce the same magnetic flux, and the device will operate happily.

You'll need to know the voltage rating if the water cart.

 

[graeme210375]

BEWARE !!
You'll need to know the voltage rating if the water cart.

The water cart takes 240v. The power simply runs a standard domestic immersion in the tank and a battery trickle charger which, in turn, charges a 12v battery to power a pump.

 

[snowhead]

The water cart takes 240v. The power simply runs a standard domestic immersion in the tank and a battery trickle charger which, in turn, charges a 12v battery to power a pump.

It's a Portable appliance, (and if it's drinking water it's a Potable appliance).

 

[Patman]

graeme -- Water cart, treat as "moveable/stationary". Earth bond 0.1 + cable length. Ins res @ 500v. Earth leakage <3.5mA. You can pick up earth on heater elements or tank (if steel) and then on casing of trickle charger.

 

[graeme210375]

graeme -- Water cart, treat as "moveable/stationary". Earth bond 0.1 + cable length. Ins res @ 500v. Earth leakage <3.5mA. You can pick up earth on heater elements or tank (if steel) and then on casing of trickle charger.

Many thanks Patman. The tank is aluminium, but the testing principles will still be the same I'd imagine. I'm going to recommend a 6 monthly inspection on the water cart as it is stored outside all year round, and used by many different people and towed around the airport. Still concerned about the Hoover's though. Possibly a visual inspection, can't find an adapter for the plugs.

 

[Adam W]

I might be tempted to contact the manufacturer.

 

[graeme210375]

I might be tempted to contact the manufacturer.

Good point. The hoover's are a mixture of Numatics and Henry's. The plugs have been fitted by the distributor and not the manufacturer, but struggling to fond out who the distributor is.

 

[graeme210375]

Ins res @ 500v. Earth leakage <3.5mA. You can pick up earth on heater elements or tank (if steel) and then on casing of trickle charger.

Was going to perform 250V IR on the trickle charger as its an inteli-charger.