Editing Overvoltage and undervoltage faults
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− | Drive faulting due to voltage fluctuations in [[HV DC bus]] are commonly experienced with servo systems. These faults occur when drive measures a HV DC bus supply voltage that is not within the range defined by | + | Drive faulting due to voltage fluctuations in [[HV DC bus]] are commonly experienced with servo systems. These faults occur when drive measures a HV DC bus supply voltage that is not within the range defined by [[FUV]] and [[FOV]] parameters. The deviation of voltage may be impossible to notice with multimeter as length of these voltage surges can be in millisecond range. |
==Overvoltage faults== | ==Overvoltage faults== | ||
− | Servo drive attached to a motor can act two ways: energy supply and energy consumer. The energy consumer behavior occurs during decelerations and during fast torque reversals, and this causes current flow from motor to drive power supply capacitors. If the generated energy is not absorbed anywhere, the voltage of HV DC bus capacitors will rise above overvoltage threshold ( | + | Servo drive attached to a motor can act two ways: energy supply and energy consumer. The energy consumer behavior occurs during decelerations and during fast torque reversals, and this causes current flow from motor to drive power supply capacitors. If the generated energy is not absorbed anywhere, the voltage of HV DC bus capacitors will rise above overvoltage threshold ([[FOV]]) and trigger an software cleanable overvoltage fault. Overvoltage faults that are caused by returned energy from motor, can be dealt with a [[regenerative resistor]] and with optional extra capacitance in HV DC bus. |
Scenarios where returned energy is causing the rise of HV DC bus voltage: | Scenarios where returned energy is causing the rise of HV DC bus voltage: | ||
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<gallery widths="330px" heights="500px"> | <gallery widths="330px" heights="500px"> | ||
− | File:regeneration1.png|Voltage generation during deceleration of motor (motor current is negative, current is pumped to HV DC bus causing a 40 VDC rise) | + | File:regeneration1.png|Voltage generation during deceleration of motor (motor current is negative, current is pumped to HV DC bus causing a 40 VDC rise). |
− | File:regeneration2.png|Voltage generation during deceleration of motor (motor current is negative, current is pumped to HV DC bus). However, in this case drive is equipped with regenerative resistor and tightly set | + | File:regeneration2.png|Voltage generation during deceleration of motor (motor current is negative, current is pumped to HV DC bus). However, in this case drive is equipped with regenerative resistor and tightly set [[FOV]] parameter which prevents the significant voltage rise (only 5 VDC rise). |
File:regeneration3accel.png|Example of accelerating motor (motor current is positive, power is drawn from HV DC bus which is causing a temporary voltage drop). Rectified 50 Hz mains AC ripple is easily seen in the voltage graph. | File:regeneration3accel.png|Example of accelerating motor (motor current is positive, power is drawn from HV DC bus which is causing a temporary voltage drop). Rectified 50 Hz mains AC ripple is easily seen in the voltage graph. | ||
</gallery> | </gallery> | ||
===Sizing regenerative resistor=== | ===Sizing regenerative resistor=== | ||
− | + | The needed regenerative resistor value can be calculated by equation: | |
<math>R_{regen}=\frac{U_{DCBusVoltage}}{I_{PeakMotorCurrent}}</math>{{mathtip}} | <math>R_{regen}=\frac{U_{DCBusVoltage}}{I_{PeakMotorCurrent}}</math>{{mathtip}} | ||
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{{damage|Before connecting a resistor to drive or drive's motherboard, check from user guides and/or electrical specifications the minimum allowed resistance. Specifications (list may be partial): [[Argon specifications]], [[IONICUBE electrical specifications]], [[IONICUBE 1X electrical specifications]]. | {{damage|Before connecting a resistor to drive or drive's motherboard, check from user guides and/or electrical specifications the minimum allowed resistance. Specifications (list may be partial): [[Argon specifications]], [[IONICUBE electrical specifications]], [[IONICUBE 1X electrical specifications]]. | ||
}} | }} | ||
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==Undervoltage faults== | ==Undervoltage faults== | ||
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===Variables used in equations=== | ===Variables used in equations=== | ||
*<math>t_{duration}</math> = time duration in seconds which capacitor should be able to help at maximum current surge | *<math>t_{duration}</math> = time duration in seconds which capacitor should be able to help at maximum current surge | ||
− | *<math>L_{MotorInductance}</math> = motor coil inductance in Henrys (use value of | + | *<math>L_{MotorInductance}</math> = motor coil inductance in Henrys (use value of [[ML]]/1000) |
− | *<math>I_{PeakMotorCurrent}</math> = motor peak current in Amps (use value of | + | *<math>I_{PeakMotorCurrent}</math> = motor peak current in Amps (use value of [[MMC]]/1000) |
*<math>U_{MaxVoltageChange}</math> = maximum voltage change in HV DC bus during this current surge/peak. I.e. if drive is set to fault at 56V and supply voltage is 48VDC, then 56-48V=8V should be used. | *<math>U_{MaxVoltageChange}</math> = maximum voltage change in HV DC bus during this current surge/peak. I.e. if drive is set to fault at 56V and supply voltage is 48VDC, then 56-48V=8V should be used. | ||
*<math>scaler</math> = a user chosen value between 0.1 to 1.0. 1.0 is for the worst case where we assume instantaneous torque reversal (rare) and lower values can be used with slower change of torque direction. | *<math>scaler</math> = a user chosen value between 0.1 to 1.0. 1.0 is for the worst case where we assume instantaneous torque reversal (rare) and lower values can be used with slower change of torque direction. | ||
− | {{tip|Drive allows voltage few temporarily volts above | + | {{tip|Drive allows voltage few temporarily volts above [[FOV]] before faulting. In IONI this voltage is about 4 volts. So when FOV is set to 52V, then drive actually faults at 56V}} |
===Surge duration based method=== | ===Surge duration based method=== | ||
For short current surges/spikes, a capacitor added to HV DC bus might provide a solution for filtering out the spikes. Capacitor can be sized by equation: | For short current surges/spikes, a capacitor added to HV DC bus might provide a solution for filtering out the spikes. Capacitor can be sized by equation: | ||
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Targeting low value in max voltage change will increase capacitor size significantly, and may become unpractical. I.e. if supply voltage is 48V and max voltage is 56V, the max voltage change would be only 8V. Reducing supply voltage by few volts, say 44V, the allowed voltage change becomes 12V which yields much smaller required capacitance (in the above inductance based method example this change would make 2.2 times difference). | Targeting low value in max voltage change will increase capacitor size significantly, and may become unpractical. I.e. if supply voltage is 48V and max voltage is 56V, the max voltage change would be only 8V. Reducing supply voltage by few volts, say 44V, the allowed voltage change becomes 12V which yields much smaller required capacitance (in the above inductance based method example this change would make 2.2 times difference). | ||
{{tip|Operating drive near maximum supply voltage limit may cause high requirements for overvoltage prevention. Sometimes it may be easier to reduce supply voltage little bit to make more headroom for voltage increase. Many switching power supplies have a trimpot allowing to adjust voltage up/down by few volts.}} | {{tip|Operating drive near maximum supply voltage limit may cause high requirements for overvoltage prevention. Sometimes it may be easier to reduce supply voltage little bit to make more headroom for voltage increase. Many switching power supplies have a trimpot allowing to adjust voltage up/down by few volts.}} | ||
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