View Full Version : forward reverse switch

Alistair Hosie
12-26-2006, 05:33 PM
I have a cup wheeled grinder fitted with a green wheel to cut tungsten carbide.It has a forward reverse switch on top the kind with a flip lever switch it is 3 phase can these switches be used with any kind of motor or only 3 phase etc ?I find it difficult to undestand how it would work with a single pphase motor but I believe I have heard that it can .Alistaair

12-26-2006, 06:52 PM
If it is like a drum switch check out page 4 of this PDF for the correct diagram:



Alistair Hosie
12-26-2006, 07:14 PM
That's it T S a Drum switch perfect thanks for the printout have printed a copy regards Alistair.

12-26-2006, 09:06 PM
Kinda funky the way they laid the terminals out in a drum switch. Lots of them are different Alistair...

Be sure before you get a face full of fire. OK? I have seen dozens of experienced electricians take it for granted they hooked up the same as the one they were replacing.

Checking with a meter is a good way to prevent mistakes. A motor has a few ohms resistance on the meter scale in the windings and you should not read (0) resistance between any two legs. If it reads (0) to the ground or leg to leg, do not energize it to see what will happen.. I can tell you what will.. okay?

You can reverse a single phase motor by switching the ends of the capacitor start winding from L1, L2.. used to be the black and blue in the pecker head (motor connection box).. 5 & 8 maybe? been more than a week and I got a headache now. See past posts on this topic.. okay?? It works by delaying the phase angle of the ac power in one direction or the other to "start" the armature going in that direction.. OK? once it comes up to speed the "points" in the end open up and it shifts that winding out..
A not-starting single phase motor, quick check to see if the start points, capacitor or winding is out? take off the belt and turn on power as you kick start it.. it can start in either direction by the way. If you switch directions on a start winding motor before the speed drops low enough for the points to kick in, it will continue in the direction it was going.

Hope this helps a tad. I still got a headache.. off to lay on the couch with the pup.

12-26-2006, 09:26 PM
UK single phase has only live, neutral, earth. David

12-26-2006, 10:58 PM
Single phase in US is the same. When reversing capacitor start single phase motors, ath capacitor connections are reversed. David is correct, it is usually 5 & 8, but not always enough to bet on it.

There are many different drum switches, and connections vary between manufacturers and series. Some are three phase only, single phase only or combination. Do not rely on a diagram that is not specific for the switch at hand unless you have proved the connections with a tester.