Showing posts with label shunt. Show all posts
Showing posts with label shunt. Show all posts
Saturday, November 5, 2016
Motorcycle Shunt Regulator Circuit using SCR
Motorcycle Shunt Regulator Circuit using SCR
The circuit presented here is a Rectifier plus Regulator for a 3-Phase charging system of Motorcycles. The rectifier is full-wave and the regulator is shunt-type regulator.
By: Abu Hafss
A motorcycles charging system is different from that on cars. The voltage alternator or generator on cars are electro-magnet type which are quite easy to regulate. Whereas, the generators on motorcycles are permanent magnet type. The voltage output of an alternator is directly proportional to the RPM i.e. at high RPM the alternator will produce high voltages more than 50V hence, a regulator becomes essential to protect the entire electrical system and the battery too.
Some small bikes and 3-wheelers which do not run at high speeds, only have 6 diodes (D6-D11) to perform full-wave rectification. They dont need regulation but those diodes are high ampere rated and dissipate a lot of heat during operation.
In bikes with proper regulated charging systems, normally shunt-type regulation is used. This is done by shorting out the alternators windings for one cycle of the AC waveform. An SCR or sometimes a transistor is used as shunting device in each phase.
For the rectifier, there are three options:
a) Six automotive diodes
b) One 3-phase rectifier
c) Two bridge rectifiers
All must be rated at least 15A and heat-sinked.
The automotive diodes are two types positive body or negative body hence, should be used accordingly. But they might be little difficult to contact to heat-sink.
If using two bridge rectifiers, they may be used as shown.
By: Abu Hafss
A motorcycles charging system is different from that on cars. The voltage alternator or generator on cars are electro-magnet type which are quite easy to regulate. Whereas, the generators on motorcycles are permanent magnet type. The voltage output of an alternator is directly proportional to the RPM i.e. at high RPM the alternator will produce high voltages more than 50V hence, a regulator becomes essential to protect the entire electrical system and the battery too.
Some small bikes and 3-wheelers which do not run at high speeds, only have 6 diodes (D6-D11) to perform full-wave rectification. They dont need regulation but those diodes are high ampere rated and dissipate a lot of heat during operation.
In bikes with proper regulated charging systems, normally shunt-type regulation is used. This is done by shorting out the alternators windings for one cycle of the AC waveform. An SCR or sometimes a transistor is used as shunting device in each phase.
The network C1, R1, R2, ZD1, D1 and D2 forms the voltage detection circuit, and it is designed to trigger at about 14.4 volts. As soon as charging system passes this threshold voltage, T1 starts conducting. This sends current to each gate of the three SCRs S1, S2 and S3, via current limiting resistors R3, R5 and R7. D3, D4 and D5 are important to isolate the gates from each other. R4, R6 and R8 help in draining any possible leakage from T1. S1, S2 & S3 should be heat-sinked and isolated from each other using mica insulator, if using common heat-sink.
For the rectifier, there are three options:
a) Six automotive diodes
b) One 3-phase rectifier
c) Two bridge rectifiers
All must be rated at least 15A and heat-sinked.
The automotive diodes are two types positive body or negative body hence, should be used accordingly. But they might be little difficult to contact to heat-sink.
If using two bridge rectifiers, they may be used as shown.
  |
| Bridge Rectifier |
 |
| Automotive diodes |
 |
| 3-phase rectifier |
 |
| Bridge Rectifier |
Available link for download
Tuesday, October 4, 2016
SCR Shunt for Protecting Capacitive LED Driver Circuits
SCR Shunt for Protecting Capacitive LED Driver Circuits
The post presents an effective method for protecting capacitive LED driver circuits through an SCR shunt regulator circuit and explains how it can prevent filter capacitors from blowing of and LEDs from getting destryed. The remedy was requested by Mr. Max Payne.
The Request
hi swagatam,
3W, 5W LED bulb circuit design fault. the LED bulb running very cool. The electrolyte capacitor (47uf to 100uf , 50v rated) keeps explode. without any reason. and wasting all LEDs but smd resistor (474 & 560), MB10S, 105j400v has no problem, This is the problem pcb of the cheapest 3W, 5W LED set.
How can i solve the problem permanently or Pls suggest me few cost effective designs ... I noted that these explosion happening when i operate induction cook-top.
The Design
A filter capacitor in a capacitive power supply will mostly blow-of due to an insurge of voltage higher than its rated value. For example if the filter capacitor breakdown voltage is 50V, and if the surge voltage exceeds this limit could instantly cause the capacitor to explode or gas.
A rather simple solution to protect the vulnerable parts in a capacitive transformerless power supply such as the capacitors and the LEDs is to introduce a shunt regulator circuit as indicated in the following diagram:
Here the SCR forms the main element for curbing the initial high voltage, high current surge and to ensure a regulated constant supply regardless of the input fluctuations.
If we recall, this concept has been already discussed in one of my earlier posts titled how to make a high current transformerless power supply circuit
The idea here is to switch ON the SCR or a triac as soon as the input supply tries to surpass the stipulated safe voltage limit of the circuit, which in turn depends on the indicated zener diode voltage.
Referring to the above SCR shunt circuit for protecting capacitive LED drivers, whenever the input from the mains capacitor tends to go above 12V, the zener diode conducts fully, triggering the SCR, and causing its anode cathode leads to short circuit the supply instantaneously. This response becomes enough to stop the voltage to rise any further and ensure that its limited within the assigned 12V range.
The stage comprising the SCR, the zener and the 1K resistors act like a high current zener diode and is employed here since the input current is much higher and beyond the capacity of a normal 1 watt zener diode, however for low current transformerless power supply circuits the SCR and the 2nos 1K resistors may be eliminated and only the 12V zener could be used for the intended regulation.
The Request
hi swagatam,
3W, 5W LED bulb circuit design fault. the LED bulb running very cool. The electrolyte capacitor (47uf to 100uf , 50v rated) keeps explode. without any reason. and wasting all LEDs but smd resistor (474 & 560), MB10S, 105j400v has no problem, This is the problem pcb of the cheapest 3W, 5W LED set.
How can i solve the problem permanently or Pls suggest me few cost effective designs ... I noted that these explosion happening when i operate induction cook-top.
The Design
A filter capacitor in a capacitive power supply will mostly blow-of due to an insurge of voltage higher than its rated value. For example if the filter capacitor breakdown voltage is 50V, and if the surge voltage exceeds this limit could instantly cause the capacitor to explode or gas.
A rather simple solution to protect the vulnerable parts in a capacitive transformerless power supply such as the capacitors and the LEDs is to introduce a shunt regulator circuit as indicated in the following diagram:
Here the SCR forms the main element for curbing the initial high voltage, high current surge and to ensure a regulated constant supply regardless of the input fluctuations.
If we recall, this concept has been already discussed in one of my earlier posts titled how to make a high current transformerless power supply circuit
The idea here is to switch ON the SCR or a triac as soon as the input supply tries to surpass the stipulated safe voltage limit of the circuit, which in turn depends on the indicated zener diode voltage.
Referring to the above SCR shunt circuit for protecting capacitive LED drivers, whenever the input from the mains capacitor tends to go above 12V, the zener diode conducts fully, triggering the SCR, and causing its anode cathode leads to short circuit the supply instantaneously. This response becomes enough to stop the voltage to rise any further and ensure that its limited within the assigned 12V range.
The stage comprising the SCR, the zener and the 1K resistors act like a high current zener diode and is employed here since the input current is much higher and beyond the capacity of a normal 1 watt zener diode, however for low current transformerless power supply circuits the SCR and the 2nos 1K resistors may be eliminated and only the 12V zener could be used for the intended regulation.
Available link for download
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