ราคาหลอด LED T8 ที่สมเหตุสมผล ปัจจุบันน่าจะต่ำกว่าหลอดละ 300 บาทแล้ว

ราคาหลอด LED T8 ที่สมเหตุสมผล
ปัจจุบันน่าจะต่ำกว่าหลอดละ 300 บาทแล้ว

ที่ผมซื้อมาใช้แพ็ค 12 หลอด สุทธิ 3,450 ฿
18W 1,700 Lumens
หรือตกหลอดละ 288 บาท
ทดสอบวัดค่าทางไฟฟ้าออกมาดีมาก...

หลอดที่ 01  224V  80mA  17.0W  18.0VA  0.93PF
หลอดที่ 02  224V  70mA  16.5W  17.4VA  0.93PF
หลอดที่ 03  223V  80mA  16.7W  17.9VA  0.93PF
หลอดที่ 04  224V  80mA  16.4W  17.7VA  0.94PF
หลอดที่ 05  224V  80mA  16.6W  17.7VA  0.93PF
หลอดที่ 06  224V  80mA  17.5W  18.6VA  0.93PF
หลอดที่ 07  223V  80mA  17.0W  18.0VA  0.94PF
หลอดที่ 08  225V  70mA  16.7W  17.7VA  0.94PF
หลอดที่ 09  224V  70mA  16.7W  17.7VA  0.94PF
หลอดที่ 10  227V  70mA  16.6W  17.6VA  0.93PF
หลอดที่ 11  227V  70mA  16.8W  17.9VA  0.93PF
หลอดที่ 12  227V  70mA  16.4W  17.3VA  0.95PF

Flowchart schematic diagram for the Control Circuit of a Forward Reverse Star Delta or Wye Delta Electric Motor Controller - A how to learn skills training guide for electric motor controller

To help facilitate for a better understanding and further learning and training on the concept of the forward reverse star delta (or wye delta) control (ckt) circuit covered in our previous article, a reversible star delta starter control circuit diagram accompanied with a flowchart diagram is presented below as a follow up learning guide which shows a schematic representation of the sequence of operation for the starting and stopping and running operation of a reversible star delta or wye delta electric motor control circuit in order to provide a visual aid to help diagrammatically visualize how the control circuit flows.

The electrical schematic diagram of a reversible star (wye) delta electric motor control (ckt) circuit:

The parts of the reversible star (wye) delta electric motor control (ckt) circuit includes:

1. Stop push button switch (Normally-Close Contact) - 1 piece
2. Forward push button switch (Normally-Open Contact) - 1 piece
3. Reverse push button switch (Normally-Open Contact) - 1 piece
4. Magnetic contactor coils (for star contactor, forward main contactor, reverse main contactor, forward delta contactor, reverse delta contactor) - 5 units
5. Timer coil - 1 piece
6. Thermal Overload Relay Contact - 1 piece
7. Forward Main Contactor Auxiliary Contact (Normally-Open Contact) - 3 pieces
8. Forward Main Contactor Auxiliary Contact (Normally-Close Contact) - 2 pieces
9. Reverse Main Contactor Auxiliary Contact (Normally-Open Contact) - 3 pieces
10. Reverse Main Contactor Auxiliary Contact (Normally-Close Contact) - 2 pieces
11. Star Contactor Contact (Normally-Close Contact) - 1 piece
12. Timer Contact (Normally-Open Contact) - 1 piece
13. Timer Contact (Normally-Close Contact) - 1 piece

Electrical Circuit for Controlling a Lifting Electromagnet for Overhead Cranes with Top Running Trolley Hoist

Electrical Circuit for Controlling a Lifting Electromagnet for Overhead Cranes with Top Running Trolley Hoist

When the need to conveniently pick up and lift heavy iron or steel objects for transferring from one place to another was seen as a necessity in heavy industrial facilities, the concept of using an electromagnet was implemented due to its ability to be turned ON and OFF which was then incorporated effectively to the hoist function of overhead cranes.

Overhead-travelling-crane magnets are electromagnetic device attached to the crane's hook to magnetically pick up heavy metallic loads for hoisting and transferring.  Cranes that are fitted with a lifting magnet are equipped with an electromagnet control circuit.

The control circuit of the electromagnet is designed with operator command switch that can power the magnet ON and OFF. The electrical system is controlled by an electronic circuit so constructed so that when the magnet is switched ON for lifting objects, it instantaneously energizes the magnet by applying electric current to produce magnetic field with enough force to pick up heavy objects by magnetic attraction to the metal surface of the object, and to also release the object after transferring it in place to a certain location by switching OFF the magnet.

Figure 1 below is an artist's rendition (that's me by the way) of a typical overhead crane with top running trolley hoist fitted with an electromagnet suspended from its hook.

Figure 1:  Typical overhead crane with top running trolley hoist fitted with an electromagnet suspended from its hook.

Although the electrical control circuit uses AC power converted to DC power which is responsible for supplying electric current to the coil of the electromagnet, the electrical system of the magnet should also be supported by an automatic transfer system that can immediately switch to back-up battery mode with a DC battery unit, this is for safety purpose to prevent any occurrence of accidental dropping of heavy metallic loads while it is suspended in midair halfway through the lifting process in case of sudden loss of AC mains power supply during electric power grid failures, and to also cope safely with instances of intermittent AC power fluctuations.

A battery charger should also be included in the control circuit of the electromagnet to ensure that the required battery power level is always maintained. The charger should be able to detect battery power depletion level and automatically charge to replenish it so that sufficient amount of electric power is efficiently available at all times to ensure that an uninterrupted supply can be expected from the battery for the electromagnet to work effectively.

The schematic diagram in Figure 2 below shows an example of a conceptualized electronic circuit intended for a typical electromagnet used for the hoist function of overhead cranes.

Figure 2: Electronic circuit schematic diagram intended to illustrate the electrical control system of a typical electromagnet for the hoist function of overhead cranes.

As mentioned earlier, the diagram above shows that the battery serves only as a backup unit and will remain idle for most of the time while the AC power supply is active in the circuit. Steady DC power comes from the rectifier's converted DC voltage. Turning the switch ON will activate the two transistors Q1 and Q2 which are connected together in parallel to withstand sufficient amount of electric current to flow across the collector to the emitter of these two transistors in order to supply adequate amount of power to the coil of the electromagnet.

The diode which is connected in series with the battery serves as a one way directional path that will block the flow of current in the opposite direction coming from the P terminal of the rectifier, since the voltage coming from the rectifier is more positive than the B+ terminal of the battery then the diode is reverse biased in such condition. When the supply voltage from the AC power source is removed, the positive side (B+ terminal) of the battery is free to flow through the forward direction of the diode, which is now forward biased to serve as substitute positive voltage to supply power to the coil of the electromagnet through transistors Q1 and Q2, in place of the missing positive voltage from the rectifier in the absence of the AC source voltage.

The B+ terminal between the diode and the positive plate of the battery is connected to the charger circuit located in the bottom part of the electronic diagram. The battery charger circuit consists of an OP Amp (operational amplifier) which amplifies the signal from the reference voltage set by the variable resistor (potentiometer) VR1. The zener diode connected across VR1 is intended as a clamp for the purpose of maintaining a fixed reference to protect the first stage OP Amp from unnecessary rise of voltage to enter the input of the first stage OP Amp.

A high input signal from VR1 is inverted to low output signal in the first stage OP Amp, which proceeds further as a low signal to the input of the second stage OP Amp where it is inverted once again as a high signal output going to the base of transistor Q3, which in turn activates transistor Q3 to supply high input signal to the base of transistor Q5. This switches ON transistor Q5 so that its positive collector voltage P, which comes from the P terminal of the rectifier, can flow down to the emitter of transistor Q5 to supply positive voltage to the battery, thus charging the battery.

Transistor Q4 serves as a comparator and also as a feedback that detects the voltage level from the battery which can be adjusted and set with a reference voltage from the variable resistor (potentiometer) VR2. When a preset feedback voltage level from VR2 is detected at the base of transistor Q4, it switches Q4 to ON state to pull down the high input signal supposedly for positive trigger input to the base of transistor Q3. Absence of the high input signal to the base of Q3 will shut OFF Q3 to remove the positive input signal to the base of transistor Q5, causing it to discontinue the flow of positive voltage P from the collector to the emitter of Q5, thus stopping the charging of the battery.

Another feedback connection is found between B+ and the input of the second stage OP Amp of the charger circuit. This is intended to check the voltage level from the B+ terminal of the battery so that when B+ is higher it will then take precedence over the low input signal of the second stage OP Amp, which will reduce the gain of this amplifier to turn OFF both transistors Q3 and Q5 to stop further charging of the battery.

The very stable DC reference voltages +15V and -15V for the charger circuit is supplied by two regulator ICs, the 7815 regulator IC outputs a steady +15V supply, while the 7915 regulator IC is responsible for supplying a very constant -15V volts.

To protect the entire electronic circuit from sudden rise of instantaneous reverse voltage from the coil of the magnet which will flow in the opposite direction to the original polarity of the supply voltage of the electromagnet after switching it OFF, a flywheel (or flyback) diode is connected across the coil of the electromagnet to serve as a shunt for back EMF (electromotive force) suppressor that catches the reversing spike voltage by shorting it out to the magnet's coil without causing damage to the electronic components of the circuit.

https://www.youtube.com/watch?v=UlmN8SU-wV0

https://www.youtube.com/watch?v=UlmN8SU-wV0https://www.youtube.com/watch?v=UlmN8SU-wV0

Internal Wiring Configuration for Dual Voltage Dual Rotation Single Phase Capacitor Start AC Motor

Internal Wiring Configuration for Dual Voltage Dual Rotation Single Phase Capacitor Start AC Motor

220 Volts Configuration:

Fig-1 Wiring Connection of a Split Phase Capacitor Start Motor supplied with 220 Volts in Forward Rotation

The drawing in Fig-1 above shows a split phase capacitor start motor supplied with a single phase 220 volts on terminal L1 and L2 of the series connected run coils 1 and 2. The start coil winding is configured in the order L1 connected to the start capacitor which is in series with the start coil 1 and the start coil 2 where its end is connected to the center tap terminal between run coil 1 and run coil 2, which provides the forward rotational direction of the motor powered by a 220 volts AC supply source voltage.

Fig-2 Wiring Connection of a Split Phase Capacitor Start Motor supplied with 220 Volts in Reverse Rotation

The drawing in Fig-2 above shows a split phase capacitor start motor supplied with a single phase 220 volts on terminal L1 and L2 of the series connected run coils 1 and 2. The start coil winding is configured in the order L1 connected to the start coil 2 and start coil 1 which is in series with the start capacitor and the centrifugal switch where its end is connected to the center tap terminal between run coil 1 and run coil 2, which provides the reverse rotational direction of the motor powered by a 220 volts AC supply source voltage.

Operating Alternators or AC Generators in Parallel

Operating Alternators or AC Generators in Parallel

Pointers for Operating Alternators in Parallel:
1) If the load of a single generator becomes too large that its rating is exceeded, it is necessary to add another generator in parallel to increase the power available from the power station. Before attempting to connect AC generator in parallel, the following conditions must be met:


1-1) The voltages of the alternators must be in phase.
1-2) The terminal voltage of the generators should be equal.
1-3) Their frequencies must be equal.

2) When two or more generators are operating in parallel where they satisfy the three requirements mentioned in item 1 above, they are said to be in synchronism. The operation in getting these machines into synchronism is called synchronizing. For clarity in the following discussions, it is assumed that one generator is running and another one to be synchronized will be called the incoming generator.

3) There are several methods of synchronizing alternators. The most common methods are by the use of bright lamp or dark lamp method and the other one is by the use of a synchroscope. The following are the stages or procedures to be followed in operating two or more alternators in parallel:

3-1) The initial step to be taken before attempting to synchronize two or more polyphase AC generators is to phase-out the leads of these alternators. Phasing-out means that the leads of the incoming AC generator will be connected to the corresponding lead of the other generator. When this is not done the generator will be damaged because of interchange of current during their operation. Figure 1 illustrates the connections to be used in phasing out two three phase alternators.

Figure 1: Phasing-out of two three phase alternator.

Assuming that the running generator is already connected to the bus, the incoming generator could now be started and made to run at synchronous speed with the circuit circuit breaker on the OFF position. Three lamps/bulbs will be connected in the circuit breaker terminals of the incoming generator as shown in Figure 1. If the three lamps become dark or bright simultaneously, the two machines are in-phase. If the three lamps do not become dark or bright simultaneously, interchange any of the two main leads of the generator. Take special care that in doing this, you have to shut off the incoming generator for your safety. If the generators are in-phase, condition 1-1 mentioned above is met.

3-2) The next step now is to adjust the voltage adjustment control of the incoming generator until its panel voltmeter registers an identical voltage with the running generator.

3-3) The third step now is to have the frequency of the incoming generator adjusted so that it would be the same as that of the running generator. This is done by raising and lowering the frequency of the incoming machine. If the dark lamp method is used (See Figure 2), engage the switch of the synchronizing lamps and wait until the lamps are dark; then, while the lamps are still dark, close the circuit breaker of the incoming generator. The incoming generator is now "on line" or in parallel with the running unit.

If the bright lamp connection is used, raise and lower the frequency of the incoming unit until the lamps are on their brightest, then close the circuit breaker of the incoming set.

Figure 2: Synchronizing two AC generators using the dark lamp method.

If a synchroscope is used, adjust the frequency as described previously until the synchroscope pointer passes very slowly to the zero position as shown in Figure 3. Close the circuit breaker of the incoming generator just before the pointer passes clockwise to the zero position.

Figure 3: A Synchroscope.

3-4) The incoming unit is now in parallel with the running unit. The next step is to divide the load proportionally between the two generating sets, increase the speed of the unit showing less than its load share in the watt-meter and reduce the speed of the other unit until proper load division is indicated.

To divide the ampere load correctly, turn the voltage control rheostat clockwise on the unit showing less than its load share on the AC ammeter and turn the voltage control rheostat counterclockwise on the other unit until the proper load division is indicated.

CAUTION: If when switching the synchronizing lights you noticed that the synchronizing lights are alternately blinking, be very careful, DO NOT CLOSE the circuit breaker of the incoming generator. This indicates that the lines are not in-phase (refer to 3-1).

How to Connect a 3 Wire DC Solid State Proximity Sensor to a PLC

How to Connect a 3 Wire DC Solid State Proximity Sensor to a PLC