This model consists of a D.C. machine and a terminal box. The D.C. machine is a two pole, compound-wound machine having a series fields, a shunt field, and an armature winding. The machine may be operated as a motor or as a generator. The field excitation (located on the stator poles of the motor but which can not be seen) may be either a shunt field, a series field, or a compound field. The ratings of the machine are:

Shunt or Series Motor : 125v, 3.5A, 1/3HP, 1800 RPM

Shunt, compound, or series generator : 115v, 2A, 1800 RPM

Shunt Field Excitation : 0.5A @ 125V

Max. Ambient Temp. : 40 C

The terminal box includes two field rheostat terminals, labeled “FLD.RHEO.” two shunt field terminals, labeled “SHUNT FLD”, two armature terminals labeled as such; and two series field terminals, labeled, “Series FLD.”. Each pair of terminals given above is number 1 and 2. There are 4 terminals for the starter switch; two are labeled L1 and L2 which are located below the other two, which are labeled T1 and T2. The starter switch is in the middle of these terminals. The field rheostat knob is located on top of the terminal box. The rheostat is rated at 300W, 100 watts, .575 Amps and has a linear taper. Its minimum resistance is obtained when it is turned fully counter-clockwise.

Below the field rheostat terminals is a 1A Slo Blo fuse.

D.C. MACHINE-MODEL DM-100D.C. MACHINE-MODEL DM-100CAUTION:

Make sure both the starter switch of the machine and the main AC breaker are OFF before making connections to the machine.

OPERATION AS A COMPOUND MOTOR

1. Turn the field rheostat fully counter-clockwise.

2. Make the connections shown in figure 1 using the 125 VDC supply connected to the two L terminal.

3. Turn on the main AC breaker, then turn on the starter switch.

4. Adjust the field rheostat or the line voltage (the latter using the voltage control knob of the d.c. supply) to set the speed of the motor.

OPERATION AS A COMPOUND GENERATOR

1. Turn the field rheostat fully clockwise.

2. Make the connections shown in figure 2 and couple the machine to a suitable prime move capable of operating at approximately 1800 RPM. Connect the load at the time.

3. Operate the prime mover and control the output voltage by adjusting the field rheostat. To supply to load, place the starter switch in the ON position.

 

Figure 1: DC Motor

Figure 1: DC Motor

The primary function of the DC motor is to demonstrate the characteristics of shunt, series, and compound motors. It may also be utilized as a prime mover when testing a generator or alternator. Using the DC motor for this purpose has the advantage that the speed may be held constant by adjusting the shunt field rheostat after each load step is applied.

 

Figure2: DC Generator

Figure 2: DC Generator

 

The DC generator is primarily utilized to demonstrate the characteristics of shunt, series, and compound generators. It is also used as the loading device when testing the various motors. WOUND-ROTOR MOTOR – MODEL WRM-100

This model consists of a wound-rotor (induction) motor situated behind a terminal box. The motor is a three-phase, four-pole motor with rotor windings connected to slip rings and brushes. It has the following ratings:

Horsepower : 1/3 RP

Speed : 1725 RPM

Voltage : 208 v 3Æ

Frequency : 60 HZ

The terminal box has 3 rotor terminals, 6 stator terminals, 6 circuit breaker terminals and the circuit breaker switch. The 3 rotor terminals are labeled A, B, and C and are schematically shown to be connected to the slip rings of the rotor. The 6 stator terminals are labeled 1 through 6 and can be used to connect the stator in a Wye or in a delta configuration. The circuit breaker has 3 lower terminals labeled L1, L2, and L3 and 3 upper terminals labeled T1, T2, and T3.