Single Phase Inverter question

eddycheong

Member
Join Date
Feb 2008
Location
singapore
Posts
15
i want to ask whether a single phase inverter can be connected to PLC?

purpose :
control the speed 1 phase induction washing machine motor.
different speed and forward/reverse direction.

i tried google/yahoo but find many power dc to ac converter.
btm is the single phase motor, capacitor and dimmer switch. My friend told me to use an inverter but cant find the details of it. if any1 can help me with the link of details about it would be much appreaciated. im kinda beginner to electrical as im an electronic student.

Motor label:
YYG-60 SPIN MOTOR
220V 50Hz 60W 0.8A 4P
5uF/450VAC IP00 CLASS E

DSC004040.JPG
 
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Where do the black and red wire go to?

The blue and green wire seem to come from a supply flex, and appear to be joined in the connector. This does not look good to me

The motor has no earth on it. Real bad

By inverter do you mean a Variable Frequency Drive, VFD
If so the motor required needs to be a 3 phase motor.

The motor you have is it a capacitor run motor, or a capacitor start motor, as the dimmer you show only works with a capacitor run motor,and the motor speed will only vary, by restricting the current, dependent on the load attached to the motor.

I feel, actually I know you are outside your level of ability, and require expert help, as this voltage level 220 volts is not to be taken lightly, as you should already know thru your electronics training.

I would be alot happier that you Get the help of an Electrician.



Added later.

The unit Moggie shows requires a 3 phase motor and will not work with your motor.
 
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the ground wire will make myself see picture below..grey wire will go to the capacitor and paralell to the purple wire

coz i havent known any electrician that could help..thats y asking here if can get any useful information


aas.JPG
 
I suggest you get some qualified electrical/electronic help locally before you power any of your circuits. As said above, you need to be very careful working with this kind of equipment and not all of it is made to do what you are seeking. Proceed with CAUTION!!!!!
 
i've already tested it with what i've bought and its already working smoothly(as in the second picture)..can use the dimmer without any problem to vary the speed..

now im planning to use an inverter to connect it to PLC and make it rev/forward direction..

the problem i cant find the inverter to match single phase motor on the web. plan to vary frequency and make it run different speed.
 
There have been a spate of questions recently about applying an inverter to a single phase motor.

Inverters are designed to be used on three phase induction motors. The design is optimized for use with that type of motor. The reason you can't find any information on the web about successful applications of inverters to single phase motors is because the number of success stories is vanishingly small.

Many low HP inverter models can be operated on single phase supply power. This confuses a lot of people into thinking that the inverter can be used to vary the speed of a single phase motor. That is a misinterpretation of the spec. The reason you can supply an inverter with single phase power is because the inverter first rectifies the incoming power and then 'manufactures' a three-phase sinusoidal output.
 
Eddy
You have to understand what a motor is. It is only a magnetic device. The rotor "chases" a rotating magnetic field. Three phase motors have at least 3 fields so the rotor easily "chases" the rotating field. VFDs simply change speed of rotation. Simple.

Motors using only 1 phase do not have a rotating field. Unless the motor is somehow tricked into turning it will simply vibrate at whatever line frequency it is connected to and the rotor will be magnetically locked.
If you do a search of this site you will find some very good descriptions about how single phase motors are started.
There are VFDs out there (do another search) for single phase motors. I don't know exactly how they work but because they must create a second phase at start up they have to be more expensive.
Good luck
 
The motor has no earth on it. Real bad

By inverter do you mean a Variable Frequency Drive,

If so the motor required needs to be a 3 phase motor.


The motor you have is a capacitor run motor, as the dimmer you show does work with a capacitor run motor,and the motor speed will only vary, by restricting the current, dependent on the load attached to the motor which is what you have observed.

Restricting of current is the only way that a single phase motor can have its speed varied, and only some types of single phase motors will allow it, capacitor run, shaded pole, and universal motors, are common, these are commonly seen in consumer products of, fans, and hand held appliances.


I would be alot happier that you Get the help of an Electrician.
 
Eddy,

Here is a thread from Sogoatticus, a guy that must have been taking the same course as you. In Post# 25 of that thread, he finally posted a picture, and it looks like the same type as your motor and controls. Sogoatticus tried using only resistance to change the speed of the motor. After must discussion and frustrution, he said that he NEVER made his PLC-controlled AC single-phase motor speed control work correctly.

http://www.plctalk.net/qanda/showthread.php?p=231991&mode=linear

If you find out what your instructor had in mind, please come back and post a detailed description, so that the next guy with this washing machine motor project will know what to do!

Somewhere in Malaysia there may be a company that makes a speed-control inverter that will work with this EXACT capacitor-run single-phase 220 volt AC motor. Only someone familar with this particular motor could answer that question.

I suspect that what you are supposed to do is disassemble that speed control device (in your picture), and figure out how it controls the motor speed. Then simulate that control using a PLC. You may need to remove the speed control pot. Leave the other speed-control devices in the circuit as they are, and wire in some resistors in the place of the vaiable resistor (potentiometer), so that the new resistors can be switched On/Off by the PLC, thus using the original device to control the speed in discrete increments. The number of spearate speed levels depends on how many resistors are used.
 
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i tried already using some resistors..and it did slow the speed..but the resistors getting ultimately hot..

if i found a single phase inverter/VFD cant the VFD connected to the PLC?
 

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