Which of the following statements with regard to DC machine, are correct?
1. Armature reaction decreases the flux under the leading pole tip in a generator.
2. Resistance commutation is generally used in fractional kW machines.
3. The polarity of the inter pole is opposite to the main pole ahead in the direction rotation for a generator.
1
1, 3
2
1 only
3
1, 2
4
2 only