DC Motor will only run in 1 direction ?
DC Motor will only run in 1 direction ?
(OP)
Hi all
Ok here is the problem, i have a small dc motor attatched to a gearbox, i have no nameplate so i will describe it in detail for you,
The field is made up of just 2 coils, connected top to bottom resistance is 1500 ohms, with 2 leads out to the terminal block, there are no interpoles fitted, there are just two leads coming from the brushgear, one from each side, im getting around 7 ohms from these leads
I fed the field 100v dc, and then fed the armature 100v dc and the motor ran ok, now i understood that if i switch over the + - leads form the field or the armature the motor should run in the opposite direction, but it dosnt it, always goes the same way, what am i doing wrong???
Ok here is the problem, i have a small dc motor attatched to a gearbox, i have no nameplate so i will describe it in detail for you,
The field is made up of just 2 coils, connected top to bottom resistance is 1500 ohms, with 2 leads out to the terminal block, there are no interpoles fitted, there are just two leads coming from the brushgear, one from each side, im getting around 7 ohms from these leads
I fed the field 100v dc, and then fed the armature 100v dc and the motor ran ok, now i understood that if i switch over the + - leads form the field or the armature the motor should run in the opposite direction, but it dosnt it, always goes the same way, what am i doing wrong???





RE: DC Motor will only run in 1 direction ?
From your measured resistances it appears that you have a shunt wound motor (i.e. the field and armature circuits are in parallel), not that this is relevant here because the above applies to both series and shunt wound motors. Are both circuits completely separate?
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
Both of the circuts are seperate, the field draws 1.7 amps, i also did a polarity test on the fiels, it had 1 north and 1 south pole so that seems to check out, its baffling me, could it possibly be the position of the brush gear?
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
If = 100 Volts/1500 Ohms = 0.066 amps?
RE: DC Motor will only run in 1 direction ?
You could try energizing the field, spinning the motor by hand and measuring the induced brush voltage. It should change polarity with a change in rotation direction.
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
RE: DC Motor will only run in 1 direction ?
The test you have done on the armature shows that this is working as expected, it seems likely then that the field circuit is the cause.
RE: DC Motor will only run in 1 direction ?