From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Procedure for conducting a light test on a motor to check mechanical friction and magnetic circuit integrity.
| Identifier | ExFiles\Box 35\4\ scan 126 | |
| Date | 19th August 1922 guessed | |
| -2- Contd. TEST 1. LIGHT TEST. The motor shall be run light for a period of half an hour on a battery of three accumulator cells in series. Towards the end of the run the current taken must not exceed 17.0 amperes. This ensures:- (a) That the mechanical friction of the motor is within reasonable limits. and(b) That the magnetic circuit of the motor is sufficiently good. The motor speed will be in the neighbourhood of 4000 R.P.M. but the speed need not be observed on this test. Current in excess of 17.0 amperes implies either or both of the following :- (a) Mechanical friction of motor is too great. (b) Provided the motor is alright as regards (a) excessive current means that the magnetic circuit of the motor is bad. This might occur as the result of too large an air gap, or of eccentricity of the armature. This latter has a double effect on the current. Firstly, because the total flux may be reduced. Secondly, because the flux may be twisted round so that the brushes are no longer in exact neutral position. Either of these will cause the current to be greater than normal. It will be seen that the light test should be quite sufficient to show up a bad magnetic circuit, provided the mechanical friction is first reduced within bounds. Contd. | ||