Servo's main task is according to the requirements of the control command, the power amplification, transformation and regulation and other processing, so that the drive output torque, speed and position control is very flexible and convenient. Servo system must have good controllability, high stability and adaptability and other basic performance. To clarify, good controllability means that after the signal disappears, it can stop immediately by itself; high stability means that the torque decreases uniformly with the increase of speed; strong adaptability means that the response is fast, sensitive, and good quality of the sound state.

Test Procedure

• The first step, first test the motor, any circuit also do not need to connect, the motor of any two of the three wires short-circuited together, rotate the motor shaft by hand, feel up resistance, that's OK.
• The second step, the drive is connected to the power supply according to the drawings (for example, with a voltage regulator, from 100V to 220V, for fear that the drive is 100V), power on, the drive is normal, there is an error message display, compared to the manual, it is showing the encoder has a fault error, this is also normal, not yet connected to the encoder it.
• Step 3, connect the encoder and turn it on again, no more error display.
• Step 4: Set the driver according to the manual. For example, set the "speed control mode", and then rotate the potentiometer, the motor did not rotate. According to the instructions in the manual, adjust the toggle switch, and finally the "Servo-ON" toggle, the motor locks, OK! Then turn the potentiometer so that there is voltage on the SPR/TRQR input pin, OK! The motor turns. Servo drive on the number of revolutions reached 1000, 2000, 3000 and finally to more than 4000 revolutions. The manual recommendation is for 3000 rpm, any higher speeds may be a bit of a problem.
• Step 5, reset the servo drive, changed to "position control mode", the motion control card (or use MACH3, connected to the computer parallel port) to the pulse, direction interface, the motor also turned! According to the output rate of 500Kpps, the drive shows 3000rpm. Forward and reverse rotation can be controlled by yourself.
• Finally, a little more adjustment of the motion control card, and the little connection board that was made. The board has an array of LEDs for testing the outputs, sockets for connecting the two-phase encoder, another socket for outputting pulses/direction, and switches and buttons for testing the I/O inputs.

Determine the quality of servo motor

Check the servo motor good or bad as follows:

• Multi-meter current measurement, three-phase unbalance rate is not greater than 10%;
• Shaking table to measure insulation, each phase to ground, phase to phase are not less than 0.5 meg;
• Bridge measurement of DC resistance, three-phase unbalance rate is not greater than 2%; that is, first of all, use a multimeter to measure the voltage as well as resistance (without shaking the table), first of all, in the motor power supply side of the UVW three-phase in the two-phase, to measure the two-phase voltage whether the two ends of the 380v (higher than the 380V is fine) due to the grid in the voltage is unstable at times caused by. Measure UV, VW, UW three-phase power supply in turn. When the power side of the measurement is completed after the measurement of the load side, measuring uv, vw, uw the resistance between the three phases of the same or say the difference is not too big, if you find that one of the pair of resistance deviates from the larger it may be the motor burned out. Finally, measure the resistance of one phase to ground is 0, so that you can determine whether the motor burned. (Motor internal take △ connection, internal connected together, so as long as the measurement of one of the phase can be)

Commonly used inspection methods

• Check the power cord voltage;
• Check switches and wiring;
• Check whether the motor rotates flexibly and remove the load test;
• Check if the motor is bad.

Fault analysis of servo motor

The servo motor can not rotate after power on, but there is no abnormal noise, and there is no odor or smoke.

Causes of failure

• The power supply is not turned on (at least two phases are not turned on);

• Fuse is blown (at least two phases are blown);

• The overcurrent relay is set too small;

• The control equipment is wired incorrectly.

Troubleshooting

• Check the power circuit switch, fuse, and junction box for breakage and repair;

• Check the fuse type, the reason for melting, and replace the fuse with a new one;

• Adjust the relay setting value to match the motor;

• Correct the wiring;

• Correct the wiring;

Servo motor does not rotate after the power is turned on

Causes of failure

• There is a broken circuit in the rotor winding (one phase is disconnected) or one phase of the power supply is de-energized;
• The beginning and end of the winding lead wire are connected incorrectly or the internal connection of the winding is reversed;
• Loose power circuit contacts and high contact resistance;
• The motor is overloaded or the rotor is stuck;
• The power supply voltage is too low;
• Small motor assembly is too tight or grease in bearings is too hard;
• The bearing is stuck.

Troubleshooting

• Identify the breakpoints and repair them;
• Check the polarity of the winding; determine if the winding ends are correct;
• Tighten the loose wiring screws, and use a multimeter to determine whether each connector is falsely connected, and repair it;
• Reducing loads or identifying and eliminating mechanical problems.
• Check for misconnection of the specified surface connection; correct for excessive voltage drop due to thin power supply leads.
• Reassemble to make it flexible; replace with qualified grease;
• Repair the bearing.

The motor is difficult to start and the speed is lower than the rated speed

Causes of failure

• The power supply voltage is too low;
• Face connection method motor misconnection;
• Rotor open weld or fracture;
• The rotor local coil is misconnected or reversed;
• Increase the number of turns too much when repairing the motor winding;
• Motor overload.

Troubleshooting

• Measure the power supply voltage and try to improve it;
• Correct the connection;
• Check for open welds and breaks and repair them;
• Identify misconnections and correct them;
• Restore the correct number of turns;
• Load shedding.

Motor no-load current imbalance

Causes of failure

• The first and last ends of the winding are connected incorrectly;
• The power supply voltage is unbalanced;
• The winding has a turn-to-turn short circuit, reverse coil connection and other faults.

Troubleshooting

• Check and correct;
• Measure the power supply voltage and try to eliminate the imbalance;
• Eliminate winding faults.

The servo motor makes abnormal noise when running

Causes of failure

• Worn bearings or foreign matter such as sand in the oil;
• Loose rotor core;
• Bearings are out of oil;
• The power supply voltage is too high or unbalanced.

Troubleshooting

• Replace or clean the bearings;
• Overhaul the rotor core;
• Go for it;
• Check and adjust the power supply voltage.

Higher servo motor vibration during operation

Causes of failure

• Excessive clearance due to wear bearing;
• Uneven air gap;
• Rotor unbalance;
• The rotating shaft is bent;
• Coupling (pulley) coaxiality is too low.

Troubleshooting

• Overhaul the bearings and replace them if necessary;
• Adjust the air gap to make it even;
• Correct the rotor dynamic balance;
• Straighten the rotor shaft;
• Recalibrate to bring it into compliance.

Servo motor bearing overheating

Causes of failure

• Too much or too little slippery fat;
• Bad oil contains impurities;
• Improper fit (too loose or too tight) between bearing and journal or end cap;
• The bearing bore is eccentric and rubs against the shaft;
• Motor end caps or bearing caps are not mounted flat;
• The coupling between the motor and the load is not calibrated, or the belt is too tight;
• The bearing clearance is too large or too small;
• The motor shaft is bent.

Troubleshooting

• Add grease (1/3-2/3 of volume) as required;
• Replace clean lubricating grease;
• Too loose can be repaired with bonding agent, too tight should be turned, grinding journal or end cap bore to make it fit;
• Repair the bearing cap to eliminate rubbing points;
• Reassemble;
• Recalibrate and adjust the belt tension;
• Replace the bearing with a new one;
• Correct the motor shaft or replace the rotor.

Servo motor overheating and even smoke

Causes of failure

• Power supply voltage is too high;
• power supply voltage is too low, the motor is running with the rated load, the current is too high for the winding to heat up;
• When repairing and removing the winding, the hot dismantling method is used improperly, which burns the iron core;
• Motor overload or frequent starting;
• The motor is out of phase and running in two phases;
• Inadequate dipping of the fixed winding after rewinding;
• High ambient temperature motor surface dirt, or blockage of the ventilation channel.

Troubleshooting

• Reduce the power supply voltage (e.g., adjust the power supply transformer tap);
• Increase the power supply voltage or change the supply wire to a thicker one;
• Overhaul the iron core to eliminate the problem;
• Load shedding; controlled starting for a specified number of times;
• Restore three-phase operation;
• Adopt secondary dipping paint and vacuum dipping paint process;
• Clean the motor, improve the ambient temperature, and use cooling measures.