Dolby
Honorary Master
- Joined
- Jan 31, 2005
- Messages
- 39,162
- Reaction score
- 6,146
-
Join the MyBroadband community
South Africa’s biggest forum. Discuss, discover, and connect with thousands of members.
-
Question of the Day: Which is the most hair-raising South African mountain pass you've driven?
Is a light and LED different load types ?
- Thread starter Dolby
- Start date
Sinbad
Honorary Master
- Joined
- Jun 5, 2006
- Messages
- 88,631
- Reaction score
- 41,143
Yes.Is this right ?
One a resistive load and the other conductive ?
Shelly 1L
shelly.cloud
Supported load type (with and without neutral):
- Resistive (lights, electric heaters)
- Inductive (Led Lights, Transformers, Fan, Motors)
Most transformers are inductive loads.
Dolby
Honorary Master
- Joined
- Jan 31, 2005
- Messages
- 39,162
- Reaction score
- 6,146
Sinbad
Honorary Master
- Joined
- Jun 5, 2006
- Messages
- 88,631
- Reaction score
- 41,143
Not really.
Inductive loads are about power factors and the fact that current and voltage aren't 100 percent in step in an inductive circuit
Justanotherguybythesea
Well-Known Member
- Joined
- Aug 9, 2018
- Messages
- 331
- Reaction score
- 159
Inductive loads are classed as any sort of load where the voltage and current into the load are not exactly in phase for the entire sine wave, and where the current and voltage are related by a constant amount, which is resistance. Any load with a motor, or other wound component with a steel laminated core operating with a winding directly energised by the mains voltage, is an inductive load, because there is no fixed relationship, and the current is out of phase with the voltage. Also covers things with diodes that rectify the incoming mains, as the current is almost zero till close to the mains peak, where there is a sudden spike of current to charge capacitors, that otherwise provide the load with power.
There are many power supplies though that use power factor correction, so the current they draw is proportional to the voltage, but to fit that into lighting is near impossible, except for very large LED light units, where the power required is high enough to fall into the regulations for power factor correction being mandatory in the EU market, so the units supplied here also will have this, small market. Most LED lamps thus are inductive or capacitive loads, and non linear. Only seen really over 100W, as it is adding nearly 50% to the cost of the power supply.
For the most part with home and light commercial metering being strictly based on real power use, and with no penalty cost for having the imaginary power metered, it makes no cost difference in power used, though it does result in the power company having to deal with higher losses in the cabling and transformers, plus also being limited supply wise in having to supply VA amount of equipment, instead of Watt amount. Only the bigger industrial customers will get 2 meters, one for real power and another for power factor, so they will be very much incentivised to make power factor correction occur, using either switched capacitor banks, line filters, which gets pretty big at MW levels, and using synchronous motors as capacitors for stationary loads, a whole other story there.
There are many power supplies though that use power factor correction, so the current they draw is proportional to the voltage, but to fit that into lighting is near impossible, except for very large LED light units, where the power required is high enough to fall into the regulations for power factor correction being mandatory in the EU market, so the units supplied here also will have this, small market. Most LED lamps thus are inductive or capacitive loads, and non linear. Only seen really over 100W, as it is adding nearly 50% to the cost of the power supply.
For the most part with home and light commercial metering being strictly based on real power use, and with no penalty cost for having the imaginary power metered, it makes no cost difference in power used, though it does result in the power company having to deal with higher losses in the cabling and transformers, plus also being limited supply wise in having to supply VA amount of equipment, instead of Watt amount. Only the bigger industrial customers will get 2 meters, one for real power and another for power factor, so they will be very much incentivised to make power factor correction occur, using either switched capacitor banks, line filters, which gets pretty big at MW levels, and using synchronous motors as capacitors for stationary loads, a whole other story there.
agentrfr
Executive Member
Depending on the design of the circuit, it could spike to a wattage near infinity but only for a very short time (charging a cap from rest can pull a million amps for a femtosecond). When dealing with AC circuits, you only consider the average over an entire cycle.
As a rule of thumb, you usually just take the RMS value, divide by 0.7 (average device power factor), then double it. You then use that rating for all of your components (e.g. Vmax for caps, Amax for relays etc.)
agentrfr
Executive Member
Eg. if your light switch powers a combined of 100 W of LED lights, 100/0.7*2 = 286 W, so make sure the smart switch is rated for 300 W