Motor drive with low leakage surge protection
A motor drive employs a combination of gas discharge tubes and metal oxide varistors to create precisely tailored surge protection that has a low leakage current minimizing the triggering of ground fault detection circuitry when multiple motor drives are attached to a single line source.
1. A motor drive with integrated surge protection comprising:
a three-phase power line input receiving AC power;
a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage;
an inverter receiving the DC bus voltage to synthesize a motor drive current and from the DC bus voltage; and
a surge protection network further comprising:
a first series connected MOV and GDT interconnecting a first line input and a common point;
a second series connected MOV and GDT interconnecting a second line input and the common point;
a third series connected MOV and GDT interconnecting a third line input and the common point; and
an MOV interconnecting the common point to ground.
2. A motor drive with integrated surge protection comprising:
a three-phase power line input receiving AC power;
a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage;
an inverter receiving the DC bus voltage to synthesize a motor drive current and from the DC bus voltage; and
a surge protection network further comprising:
a first MOV interconnecting a first dine input and a second line input;
a second MOV interconnecting a second line input and a third line input;
a third MOV interconnecting a third line input and the first line input;
a fourth MOV connected in series with a first GDT interconnecting the first line input and ground;
a fifth MOV connected in series with a second GDT interconnecting the second line input and ground; and
a sixth MOV connected in series with a third GDT interconnecting the third line input and ground.
3. The motor drive of claim 2 further comprising:
a fourth GDT connected in series with the first MOV between the first line input and the second line input;
a fifth GDT connected in series with the second MOV between the second line input and the third line input; and
a sixth GDT connected in series with the third MOV between the third line input and the first line input.
4. A motor drive with integrated surge protection comprising:
a three-phase power line input receiving AC power;
a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage;
an inverter receiving the DC bus voltage to synthesize a motor drive current and from the DC bus voltage; and
a surge protection network further comprising:
a first MOV interconnecting a first line input and a common point;
a second MOV interconnecting a second line input and the common point;
a third MOV interconnecting a third line input and the common point; and
a series connected MOV and GDT connecting the common point to ground.
5. The motor drive of claim 4 wherein each of the MOVs and the GDT are rated for breakdown voltage greater than the peak value of the AC input line voltage.
6. A method of: providing electrical protection to a motor drive of a type connected to a three-phase power line input to receive AC power at a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage, and further having an inverter receiving the DC bus voltage to synthesize a motor drive current from the DC bus voltage, the method comprising the steps of:
interconnecting a first line input and a common point with a first series connected MOV and GDT;
interconnecting a second line input and the common point with a second series connected MOV and GDT;
interconnecting a third line input and the common point with a third series connected MOV and GDT; and
interconnecting the common point to ground with a MOV.
7. A method of: providing electrical protection to a motor drive of a type connected to a three-phase power line input to receive AC power at a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage, and further having an inverter receiving the DC bus voltage to synthesize a motor drive current from the DC bus voltage, the method comprising the steps of:
interconnecting a first line input and a second line input with a first MOV;
interconnecting a second line input and a third line input with a second MOV;
interconnecting a third line input and the first line input with a third MOV;
interconnecting the first line input and ground with a fourth MOV connected in series with a first GDT;
interconnecting the second line input and ground with a fifth MOV connected in series with a second GDT; and
interconnecting the third line input and ground with a sixth MOV connected in series with a third GDT.
8. The method of claim 7 further comprising the steps of:
interconnecting a fourth GDT in series with the first MOV between the first line input and the second line input;
interconnecting a fifth GDT in series with the second MOV between the second line input and the third line input; and
interconnecting a sixth GDT in series with the third MOV between the third line input and the first line input.
9. A method of: providing electrical protection to a motor drive of a type connected to a three-phase power line input to receive AC power at a rectifier unit communicating with the power line input and converting the AC power to a DC bus voltage, and further having an inverter receiving the DC bus voltage to synthesize a motor drive current from the DC bus voltage, the method comprising the steps of:
interconnecting a first line input and a common point with a first MOV;
interconnecting a second line input and the common point with a second MOV;
interconnecting a third line input and the common point with a third MOV; and
connecting the common point to ground with a fourth MOV connected in series with a GDT.
10. The method of claim 9 wherein the each of the MOVs and the GDT are rated for breakdown voltage greater than the peak value of the AC input line voltage.