I have noticed that more and more participants on this forum are using, or are considering using VSD's with their grinders.
I wanted to pass on a few bits of general advice on how best to use these since I work in the R&D department of a company that manufactures VSD's and I don't want to see, or hear about any of you getting hurt while using one. I am not pushing my employer's products. They are not widely distributed outside of New Zealand and Australia and they have features that make them expensive for their power ratings.
For the sake of safety, PLEASE get the help of a qualified electrician with industrial, not just residential, experience to help you plan your installation. If you did the wiring, then have him check everything BEFORE you turn it on for the first time. Many of these VSD's will be working at higher voltages than you would normally find in your house. Consequently, some of the components such as circuit breakers and switches will be quite different to what you will find at your typical home-improvement store.
Your VSD contains a capacitor bank that stores a large amount of energy. Turning off the supply to your VSD does not render it safe to work on it's wiring. The capacitors must be allowed to discharge first before touching the terminals to make any wiring changes. Some VSD's may have an LED (like a lamp) that will indicate that there is still some stored charge in it. The manual should indicate if it has this feature. Please DO NOT even think about shorting out the capacitor bank using a screwdriver. Just wait. If your VSD has a set of terminals marked "+" and "-", you can use a voltmeter to check that the voltage has gone to near zero. If you don't understand the previous sentence clearly, let your electrician do all the wiring for you.
As I had stated in another post, VSD's do not work anything like a transformer, so one cannot use the same kind of thinking when looking at the ratings etc.
Check specifications for your VSD to ensure that it is dust-proof or splash-proof (I think that most are not). A sure sign that it is not is if you can look through the slots or holes in the enclosure and see any circuit boards or bare electrical connections. If your VSD is not dust-proof or splash-proof you will have to take some precautions when mounting it. Make sure that it can get lots of cool, CLEAN air. It may be simpler to mount it in another room and pass the wires through a wall. Our customers often have a "clean and cool" room where they put all of their VSD's and other elecronic equipment. A VSD with a remote mountable display makes this much easier.
Since the dust from your grinder is often conductive, there is the strong possiblity that any dust build up inside can cause a short circuit. This may damage your VSD, your motor, and possibly you. We get lots of VSD's in our service department where they have to wash them out before repairing them. Any dust build up on the heatsink in the VSD will reduce its efficiency. This can lead to the VSD "tripping" in some way or possibly cause the power devices in it to be damaged. Please note that a large amount of energy is stored inside the VSD so when it shorts out, it can sound as loud as a shotgun being fired in your shop. There is also the possibility of hot pieces of metal or plastic being ejected. Don't ask me how I know.
Make sure that you get access to the manual for your VSD. You will need it to adjust all the settings properly. You will also need it to set up all of the safety trip functions so that your motor is properly protected. If you got it used, it may still have the settings from the previous installion in it and they may make it work really wierd on your installation. Again, don't ask me how I know.
If your motor (it must be a 3-phase) is not rated for use with a VSD and you are running it in a hot environment, you may experience premature failure of the motor. The VSD's put out a lot of high frequencies and the insulation rating of the wires used in the motors typically falls with higher frequencies and higher temperatures.
Make sure that you follow the manufacturer's recommendation for earthing the motor to the VSD and the VSD itself. Otherwise you can have a safety hazard. You may also get a lot of interference that disrupts the reception of your radios and TV's (and that of your neighbor's too).
If you are purchasing one, see if you can return it if it does not work propeerly in your installation. Also, get some help from someone who is familiar with that particular brand of VSD when chosing the model that you will buy. Many of the manufacturers lie about their ratings or there are some hidden "gotcha's" about what you can or cannot do.
I hope that my comments have not put anyone off using a VSD on their grinder, or other power tool. A power tool connected to a properly set up and adjusted VSD is a joy to use. We have one connected to the drill press in our workshop at work. Of course, I also have some old prototypes under my desk for when I set up my own shop at home ;-).
Sorry for the long post. I hope that some of you find it useful and hopefully it saves you some grief.
Happy grinding.
Phil
I wanted to pass on a few bits of general advice on how best to use these since I work in the R&D department of a company that manufactures VSD's and I don't want to see, or hear about any of you getting hurt while using one. I am not pushing my employer's products. They are not widely distributed outside of New Zealand and Australia and they have features that make them expensive for their power ratings.
For the sake of safety, PLEASE get the help of a qualified electrician with industrial, not just residential, experience to help you plan your installation. If you did the wiring, then have him check everything BEFORE you turn it on for the first time. Many of these VSD's will be working at higher voltages than you would normally find in your house. Consequently, some of the components such as circuit breakers and switches will be quite different to what you will find at your typical home-improvement store.
Your VSD contains a capacitor bank that stores a large amount of energy. Turning off the supply to your VSD does not render it safe to work on it's wiring. The capacitors must be allowed to discharge first before touching the terminals to make any wiring changes. Some VSD's may have an LED (like a lamp) that will indicate that there is still some stored charge in it. The manual should indicate if it has this feature. Please DO NOT even think about shorting out the capacitor bank using a screwdriver. Just wait. If your VSD has a set of terminals marked "+" and "-", you can use a voltmeter to check that the voltage has gone to near zero. If you don't understand the previous sentence clearly, let your electrician do all the wiring for you.
As I had stated in another post, VSD's do not work anything like a transformer, so one cannot use the same kind of thinking when looking at the ratings etc.
Check specifications for your VSD to ensure that it is dust-proof or splash-proof (I think that most are not). A sure sign that it is not is if you can look through the slots or holes in the enclosure and see any circuit boards or bare electrical connections. If your VSD is not dust-proof or splash-proof you will have to take some precautions when mounting it. Make sure that it can get lots of cool, CLEAN air. It may be simpler to mount it in another room and pass the wires through a wall. Our customers often have a "clean and cool" room where they put all of their VSD's and other elecronic equipment. A VSD with a remote mountable display makes this much easier.
Since the dust from your grinder is often conductive, there is the strong possiblity that any dust build up inside can cause a short circuit. This may damage your VSD, your motor, and possibly you. We get lots of VSD's in our service department where they have to wash them out before repairing them. Any dust build up on the heatsink in the VSD will reduce its efficiency. This can lead to the VSD "tripping" in some way or possibly cause the power devices in it to be damaged. Please note that a large amount of energy is stored inside the VSD so when it shorts out, it can sound as loud as a shotgun being fired in your shop. There is also the possibility of hot pieces of metal or plastic being ejected. Don't ask me how I know.
Make sure that you get access to the manual for your VSD. You will need it to adjust all the settings properly. You will also need it to set up all of the safety trip functions so that your motor is properly protected. If you got it used, it may still have the settings from the previous installion in it and they may make it work really wierd on your installation. Again, don't ask me how I know.
If your motor (it must be a 3-phase) is not rated for use with a VSD and you are running it in a hot environment, you may experience premature failure of the motor. The VSD's put out a lot of high frequencies and the insulation rating of the wires used in the motors typically falls with higher frequencies and higher temperatures.
Make sure that you follow the manufacturer's recommendation for earthing the motor to the VSD and the VSD itself. Otherwise you can have a safety hazard. You may also get a lot of interference that disrupts the reception of your radios and TV's (and that of your neighbor's too).
If you are purchasing one, see if you can return it if it does not work propeerly in your installation. Also, get some help from someone who is familiar with that particular brand of VSD when chosing the model that you will buy. Many of the manufacturers lie about their ratings or there are some hidden "gotcha's" about what you can or cannot do.
I hope that my comments have not put anyone off using a VSD on their grinder, or other power tool. A power tool connected to a properly set up and adjusted VSD is a joy to use. We have one connected to the drill press in our workshop at work. Of course, I also have some old prototypes under my desk for when I set up my own shop at home ;-).
Sorry for the long post. I hope that some of you find it useful and hopefully it saves you some grief.
Happy grinding.
Phil
