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Variable ac controller?
- Thread starter L6steel
- Start date
- Joined
- Oct 18, 2001
- Messages
- 20,978
This looks to have some great info in it, btw...I know that doesn't answer your question, but I wanted to post it anyway...
http://www.joliettech.com/motor_selection.htm
http://www.joliettech.com/motor_selection.htm
Micheal
Do you have a variac (variable transformer), a DC motor controller, an AC motor controller or some other form of AC voltage controller (such as a high power light dimmer)?
Please post here everything that is printed on any "nameplate" or labels that you find on your unit.
Phil
Do you have a variac (variable transformer), a DC motor controller, an AC motor controller or some other form of AC voltage controller (such as a high power light dimmer)?
Please post here everything that is printed on any "nameplate" or labels that you find on your unit.
Phil
- Joined
- Nov 27, 1999
- Messages
- 3,745
Sorry Michael. If it is marked as 0-120 volts it very likely will not work. It is hard to control the speed on larger (Soft start) AC motors. On any motor AC or DC, when you reduce the voltage, it draws a greater amount of current to supply the needed wattage:
Volts X Amps = Watts
This current can be handled to a certain degree by DC motors but because of the polarity shift in AC, it causes much more heating in the coils and brushes. In other words, smoke and ozone.
The speed controllers that you get for routers and drills change the cycle rate for AC. 60 hertz is normal for this country. They work OK unless it uses a cap to soft start the motor. The motor won't come to speed and burns up quickly.
Volts X Amps = Watts
This current can be handled to a certain degree by DC motors but because of the polarity shift in AC, it causes much more heating in the coils and brushes. In other words, smoke and ozone.
The speed controllers that you get for routers and drills change the cycle rate for AC. 60 hertz is normal for this country. They work OK unless it uses a cap to soft start the motor. The motor won't come to speed and burns up quickly.
- Joined
- Sep 23, 1999
- Messages
- 5,855
Phil, it's a Variac.
The output is 0-130 volt, 60 htz. 3 amp protection, max 300 va.
I bought it online from a gent that said it was a dc power supply. I was going to build an anodizer. I didn't open it for a couple months and when I did I was poed to find out it was an ac supply and the jerk just thru in two radio shack rectifiers with it.
The output is 0-130 volt, 60 htz. 3 amp protection, max 300 va.
I bought it online from a gent that said it was a dc power supply. I was going to build an anodizer. I didn't open it for a couple months and when I did I was poed to find out it was an ac supply and the jerk just thru in two radio shack rectifiers with it.
Micheal
I don't think that a variac will work properly for controlling the speed of an AC motor. I think that what Peter said is correct. Also, the capacitor in the capacitor start motors are meant to be dissconnected by a centrifugal switch when the motor gets near it's rated speed. When you vary the speed of the motor, the capacitor never gets disconnected. The motor is not designed to have the capacitor in circuit all the time and both are likely to overheat if the motor runs for more than a few seconds with the capacitor connected.
Your variac with diodes is still considered a DC supply. It is just not a filtered DC supply. It will have 120Hz ripple on it. I have never done anodizing so I don't know if the ripple is acceptable. It may change the colors that you get on your Titanium. Adding a large electrolytic capacitor will smooth out the ripple. Let me know if you need help selecting or finding an appropriate capacitor. One of my former co-workers used to design DC supplies for plating tanks that were just much larger versions of what you have. Your car battery charger is similar too, just not variable.
Please note that your variac has a 300VA power limit. Take your output voltage and multiply it by your output current (P = V X A). The power that you put into your load should less than 300VA or you will overheat your variac and burn out the windings. It will not really be feasible to repair such damage. It is probably best to stay under 75%-80% of this figure for safety since it is hard to know if the 300VA is a short term or continuous rating.
Phil
I don't think that a variac will work properly for controlling the speed of an AC motor. I think that what Peter said is correct. Also, the capacitor in the capacitor start motors are meant to be dissconnected by a centrifugal switch when the motor gets near it's rated speed. When you vary the speed of the motor, the capacitor never gets disconnected. The motor is not designed to have the capacitor in circuit all the time and both are likely to overheat if the motor runs for more than a few seconds with the capacitor connected.
Your variac with diodes is still considered a DC supply. It is just not a filtered DC supply. It will have 120Hz ripple on it. I have never done anodizing so I don't know if the ripple is acceptable. It may change the colors that you get on your Titanium. Adding a large electrolytic capacitor will smooth out the ripple. Let me know if you need help selecting or finding an appropriate capacitor. One of my former co-workers used to design DC supplies for plating tanks that were just much larger versions of what you have. Your car battery charger is similar too, just not variable.
Please note that your variac has a 300VA power limit. Take your output voltage and multiply it by your output current (P = V X A). The power that you put into your load should less than 300VA or you will overheat your variac and burn out the windings. It will not really be feasible to repair such damage. It is probably best to stay under 75%-80% of this figure for safety since it is hard to know if the 300VA is a short term or continuous rating.
Phil