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3. How can I protect an alternator/user ?

4. Is it possible to connect a welding machine to my generating set ?

1. What is the meaning of LWA100 and what is the relation between LWA & dB(A) ?

Sound level:

We provide a real sound comparison on our website. Check it out and hear the difference  yourself.

CLICK HERE FOR THE SOUND COMPARISON.

The current European standard claims that all generators > 2kVA may not exceed LWA100.

LWA100 corresponds with 75 dB(A) at a distance of 7m.

We can say that dB(A) on 7m = LWA - 25.

dB(A) on 4m = LWA – 20

dB(A) on 0m = LWA – 0 = LWA

The sound level depends on the type of engine (gasoline or diesel), the number of revolutions and the cooling system. In general we can say that:

• a gasoline engine makes less noise than a diesel engine
• 1500 rpm is more quiet than 3000 rpm
• water-cooled is more quiet than air-cooled

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2. What is the consequence of the New European directive on permissible sound power level  for power generators and welding generators?

(document 2000/15/EC in the official Journal of the EC on March 22, 2000)

Generators in general have to become more silent.

The directive shall be carried out in 2 stages, one from 2002 on and the second one from 2006 on. 

THE THEORY

P.S. The permissible sound power level shall be rounded to the nearest whole number.

EXAMPLES

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3. How can I protect an alternator/user ? 

An alternator of a generating set can be protected in three different ways:

A) THERMAL-MAGNETIC PROTECTION

The TMP protects the alternator against overload and short circuit.

In case of overload the TMP shall switch off after a determined period of time. This period of time depends on the kind of overload: the higher the overload, the shorter the time needed by the TMP to switch off.

In case of short circuit, the TMP always switches off immediately.

The ELP automatically interrupts the circuit when an earth leakage failure occurs between (a) phase(s) and the earth which exceeds 30, respectively 100 or 300mA, depending on the type of earth leakage switch used.

The ELP protects persons against electric shocks in case of indirect contact. Moreover, the ELP also serves as a protection against short circuit. An earth pin is required in most cases !

An insulation protection relay is used to measure and guard the insulation (resistance) between not earthed AC- mains and a free chosen earth (= the frame or the mass of the generating set). In this way the user is protected against undesired contact with the AC- mains.

When an insulation default occurs the tension of the alternator can be interrupted, the engine can be stopped or an alarm can be activated. An earth pin is not required here!

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4. Is it possible to connect a welding machine to my generating set ?

When you want to couple a welding transformer to your generating set, make sure that your generator is much stronger (that it has more kVA) than your welding machine. Otherwise you will seriously damage your alternator and capacitors might blow. In all cases, we do not recommend to use welders on a generator set, unless there is sufficient overpower and a well calculated thermal-magnetic protection installed. 

Only when you have an invertor (electronic welding device), you can work safely. When you want to weld frequently, we suggest you to buy a welding generator which will cause no problems at all.

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5. How can I determine the necessary power of a generator ?

We propose a simple, practical way to determine the necessary power of a generator in five steps:

1. Make a list of all the appliances (charges) and machines which will be connected to the generating set.
2. Note down for every machine the power in Watt, the kind of charge (resistive / inductive) and the Power factor or cos phi.
3. When cos phi = 1, then: 1 VA = 1 W.
   When cos phi < 1, then: VA = W / cos phi
   For electric motors (rule of thumb): take the power of the electric motor in HP and multiply it by 2.This is how we calculate the number of kVA the generator needs for starting the electric motor.
4. Add all the obtained power in VA.
5. Use a safety margin of ± 20% on the result of step 4.
   The conversion of the HP’s of the electric motor into the kVA’s of the generator is a THUMB RULE which is correct in 90 % of the cases but NOT ALWAYS !!!

When using this procedure to determine the necessary power of the generating set, you have to be sure that the power stated by the manufacturer of the generator is the real power, not the "commercial" power

EXAMPLE: your need a generator for a 500 Watt heater, 5 strip lights of 50 Watt and a compressor of 2 HP.

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cos phi: power factor: with alternating current the absorbed (or apparent) power (kVA) of an inductive charge is larger than the active power (kW) really used by the charge.

Cos phi= active power/apparent power.

Examples:

A. Resistive charges such as light bulbs and heating elements: cos phi = 1

B. Inductive charges:

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