ROTARY CONVERTERS 99 



and divided into five equal parts. A point of reference 

 is then marked on the field, opposite to which the marked 

 positions of the armature are placed for the successive 

 starts. 



Having brought point No. 1 opposite the reference 

 point, the alternating current switches should be closed 

 and the field on the alternator increased until about 

 one-half normal full load current is sent through the 

 rotary, reading volts and amperes in the various phases. 

 As it is impracticable to read all phases at once during 

 the start, the ammeter should be cut into that phase which 

 shows the highest current and the voltmeter across 

 the phase which indicates the highest voltage, in order 

 to get the maximum readings at the instant of starting. 

 The field of the generator should be increased until 

 the armature begins to revolve, when volts and amperes 

 input and induced volts on the field should be read. 

 The voltage across the collector rings should then be 

 held constant until the rotary reaches synchronism, 

 the time required to reach this point from the start 

 being noted. 



There are several methods of determining whether 

 the rotary is in synchronism; one, by the fact that the 

 induced volts field will fall to zero; another, that the 

 voltmeter across the armature will read a definite vol- 

 tage, which will vary from a negative to a positive 

 reading if the rotary is below synchronism. Readings 

 of volts and amperes should be taken on all phases 

 after the rotary has reached synchronism. The machine 

 should then be shut down, the armature brought to 

 position No. 2, and the test repeated. In this manner 

 all five points should be tested. After these tests have 

 been made, the time required to bring the rotary to 

 synchronism should be taken by throwing one-half 

 voltage across the collector rings. 



Starting Tests from Direct Current End 



When starting from the direct current end, the 

 rotary must be wired to a direct current generator of 

 ample capacity. The rotary should be separately 

 excited with a field current corresponding in value to 



