1 , By observing the shape of the transformer is to check whether there are significant anomalies. If the coil wire is broken , Desoldering, there are burn marks or not for the insulation material, whether the core fastening screw of the LED flood light loose and the silicon steel rust and the windings expose and so on.
2, the insulation test . Use a multimeter R × 10k to respectively measure the core and primary of the LED flood light, primary and the secondary , core and the secondary, electrostatic shielding layer and panties secondary , secondary resistance value between the windings . Multimeter pointer refers to the infinity position which should not move , otherwise , indicating poor performance of transformer insulation of the LED flood light.
3 , the detection coil is off . Place the multimeter R × 1, if a winding resistance is infinite , then there is open circuit failures of this winding.
4 , determine primary and secondary windings. The primary pin and secondary pin of the Power transformer are respectively generally drawn from both sides and the primary winding mostly is marked with 220V and the secondary winding is marked with rated voltage , such as 15V, 24V, 35V , etc. , according to these marked for identification.
5 , no-load current detection .
Direct measurement. open all the secondary winding and put the multimeter in AC current 500mA, string into the primary winding . When the primary winding of the plug into 220V AC power , what the multimeter indicate is the load current value. This value should not exceed the 10 % -20% of the full load current of the transformer. The normal load current of the power transformer of general common electronic equipment should be about 100mA . If out too much, then the transformer of the LED flood light short-circuit .
Indirect measurement. Series with a 10/5W resistor in the primary winding of the transformer，the secondary still full load. Dial the multimeter to the AC voltage . After power，use the two probe to measure the voltage drop R U across the resistor, then use Ohm’s law to calculate the load current -I empty, that I empty = U / RF.
6 , temperature testing. The allowable temperature rise of the small power transformers is generally 400C ~ 500C, if the insulating material is of good quality , but the allowable temperature also can be improved.
7 , detect and discriminant dot end of each winding . When using AC adapter of the LED flood light, sometimes two or more secondary windings can be in series to use in order to obtain the required secondary voltage. Adopt the series method to use the power transformer , the same name ends of the each winding participating in series must be properly connected , which should not go wrong, otherwise , the transformer is not working properly .
8 , comprehensive detection and discriminant of the short circuit fault of the power transformer of the LED flood light. the main symptoms of the short circuit of the Power transformer are fever and serious disorders of the output voltage of the secondary winding . There are usually more points of the short circuit inside the coil inter-turn， the greater the short-circuit current，the more seriously the transformer fever. The simple method of testing determining whether the circuit of the Power transformer is short is to measure the load current of the LED flood light. For the transformer existing the short-circuit fault , the no-load current value will be greater than 10% of full load current . When the short circuit is severe, the transformer will rapidly heat after no-load power for tens of seconds, there is a hot feeling when touching the core. At this point，we can judge that there is short circuit for the transformer of the LED flood light without measuring the load current.
Browsing http://www.lead-lighting.com for more information about the LED flood light and other LED lighting.
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