Phase Analog Resolver Testing

"Phase Analog" style resolvers are wired in reverse of normal resolvers. Instead of using the standard setup of the reference winding on the rotor (Rotor Primary), the Phase Analog type have the reference winding in the stator (Stator Primary). 

Tamagawa phase analog resolvers include the BRT series, while the BRX series use the standard method.  Harowe phase analog resolvers include the BRCT and BRW series, while the BRCX and BRX use the standard method. Phase analog resolvers have been documented being used on Allen Bradley 1326AB Bulletin motors, Velconic VLBSE motors, and others.

Testing Methods

Our equipment is not designed to power the Phase Analog types, but wiring them in the normal manner (reverse of the resolver design) on the JX testers and 5000EX often will work if you use the full 8V. Keep in mind that the Vector Level will be much lower than normal, and if not above 2.0V then the color will show as yellow on the JX. Anything above 1.5V should be a strong enough signal to proceed with testing as normal. If the Vector Level is below 2.0V then the 3000JX will prevent you from running due to "Low Vec Level". Simply press the 0 button on the keypad at this warning screen to bypass the error and proceed with the run. 

Some of the Allen Bradley 1326AB motors have the added confusion of using a capacitor in the excitation circuit using the standard wiring method. The reactance of the capacitor further reduces the amplitude of the excitation and resulting sine/cosine amplitudes. At lower excitation frequencies the capacitor also introduces a phase shift that can change the angle by 180 degrees which can even result in misalignment. The reactance of the capacitor can be overcome to an extent by using a very high excitation frequency, typically around 11 – 15 KHz. Shorting out the capacitor and using a more standard 6 – 8 KHz is the safer approach.

Legacy TI-3000 Run Issue

The legacy TI-3000 uses an older resolver circuit which can not be voltage adjusted like the 5000EX and JX testers. The TI-3000 has a standard 3.5V resolver output that can only be cut in half to 1.75V. Try setting the TI-5000EX to 3.5V to simulate the signal quality going to the TI-3000. You may notice the resulting Vector Level is way too low for a dependable reading. In general, Phase Analog resolvers are not compatible to run on the legacy TI-3000. 

Resolver Wiring Methods

Most resolvers are designed to produce feedback position by applying an excitation voltage to the resolver rotor winding (EXC/EXC*) and calculating angular position based on the amplitudes of the sine (SIN/SIN*) and cosine (COS/COS*) voltages returned from the resolver stator, with a 90 degree offset between them. This is how our testers were designed to read the resolver’s angular position. The diagram below shows this standard arrangement with common wire colors.

Figure 1: Standard Resolver Wiring (Rotor Primary)

A less common resolver design is described as phase analog. With the phase analog method, excitation voltages 90 degrees apart are applied to the sine and cosine windings while the resultant output signal is taken from the stator winding.

Figure 2: Phase Analog Resolver Wiring (Stator Primary)

Notes

Resolver signals are susceptible to electrical noise pickup. Since the voltages are used to calculate the angle, changes in the voltage due to noise spikes can affect the angle calculation. View the sine/cosine voltages on a scope using the breakout board with the motor running slowly to evaluate the noise pickup. Be sure to use the GND wire from the motor power connector to the drive chassis to help with noise reduction. Keep the motor power leads as far from the resolver leads as possible. Use a shielded resolver cable. Excessive noise often results in a clicking sound from the motor indicating that the commutation may not be switching smoothly. When you hear that sound, you will generally see excessive noise on these lines.