More electrical than electronics. - Page 1
Forum section: electronics / general

author: G7PSK
author_rank: Super Contributor
timestamp: December 06, 2013, 06:26:32 pm
content: I have just got a 1 KW electric motor with gearbox from E bay, it was advertised as single phase but when it arrived today I found that it was a Tornado G90/120 compound wound DC motor with the armature voltage at 150 and the shunt field 280 volts. I want to be able to reverse the motor which would mean not only reversing the armature or shunt field but also reversing the series field in relation to the armature, I was wondering in order to simplify switching could I safely leave the series field out of circuit, the motor will only run for about 30 seconds a time and no where near 1 KW power is required for the job as the original motor was only 12 volts at about 40 watts. The reason I am fitting such a big motor is I am fed up with replacing motors on this sliding gate due to the end of the shaft which is 10 mm dia. breaking off as soon as the weather gets cold, I have fitted 5 motors in as many years to date. I am hoping that running without the series field will not lead to motor burn out, myself I cannot see a problem due to the short run times but other opinions are very welcome.

author: SeanB
author_rank: Super Contributor
timestamp: December 06, 2013, 06:42:47 pm
content: You can lose the series winding as you want. Will affect regulation a lot but as you are going for a low duty cycle you just have to drive the armature as a simple shunt motor. Just use a transformer and big bridge rectifier to give you 150VDC for both shunt and armature ( 220 to 110VAC works), will slow it down a little and still have enough power to drive the gate. Just remember to have a relay contact that shorts the windings with a low value series resistor ( to save the relay contacts more than anything, a resistor under 5R or so will be fine and with a 20-50W rating) to get a fast stop and dump the stored energy and inertia fast. If you do not have a shorting action when stopping you will probably shear the drive gears off the gate or drive it off the end stops or bend it or the post.

author: G7PSK
author_rank: Super Contributor
timestamp: December 06, 2013, 10:13:43 pm
content: I was toying with the idea of using the series winding as the braking resistance by switching it into parallel with the armature on switch of. All the control would be from the original gate electronics. But after finding this via a Google search I wonder whether I should try to sell it and buy another motor, I paid £41.00 plus another £40 to get it to me but these people are selling them second hand in a more beat up condition than the one I got for over $1,800 US.http://www.sabinadrives.com/Tornado-DC-Gearmotor-1kw-2400-150-280v-VDE0530-p/g90-120-sv691.htm

author: SeanB
author_rank: Super Contributor
timestamp: December 07, 2013, 01:46:28 pm
content: If you can sell it then do so. What gate motors are you using ( along with the size of the gate) that die after a year. I get a decade or so out of the commercial ones I buy.

author: G7PSK
author_rank: Super Contributor
timestamp: December 07, 2013, 04:12:34 pm
content: The gate control and motor are an Italian make, Coel is the name. When the first one broke the supplier told me that motors were not available on their own and I would have to buy another motor and gear box complete at £400.00 I took the motor out and goggled the numbers on it and found the motor manufacturers Electro parts in Italy I bought 5 motors from them for 12 euro's each plus transport which came to more than the motors, this time when I approached them they did not even bother to answer, the company web site is still working so I presume they are still in business but are not interested in the small quantity I want. But I guess if I sold the motor for any where near what that US company are asking I could buy a complete new motor and control gear. The main problem with my gate is its 7 meters long 2 meters high and built from 60 x 12 black bar with 20 mm rails and weighs around 500 kgs. so its rather pushing these motors which are ratted to 600 kgs. one reason I thought I would build my own motor unit.

author: SeanB
author_rank: Super Contributor
timestamp: December 07, 2013, 07:52:37 pm
content: Buy a Centurion A10 and fit it. Survives out here in the harsh conditions and works. If the gate is lighter then a D10 or a D5 will do as well. Currently I am using a Vector on a gate and a few R5 units, and they are pretty reliable, and a lot cheaper to maintain than the previous BFT units. Had to replace an actuator after about 6 years of operation and bought a new one instead of getting it serviced and refurbished as that was faster. Cost about GBP200 for that.