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Motor Guard is a patented motor testing and protection system designed to monitor winding insulation breakdown in critical duty motors.
Meg-Alert has created a patented, automatic, in-line insulation resistance tester and monitor with test capabilities from 500 to 5000 VDC. Downtime and maintenance costs are reduced as critical motors are pulled out of production as part of a preventive maintenance program rather than after a catastrophic failure. Personnel safety is improved and adherence to a preventive maintenance schedule enhanced as Motor Guard testing is conducted automatically rather than manually. In effect, Motor Guard provides the peace of mind that comes from meg ohm testing the motor windings before every start.
Features
- Auto/manual test operation
- Flashing L.E.D. display with test and fault indication
- Adjustable alarm/fault setpoint with latching contacts and manual reset capability
- Full 500 VDC test voltage
- Fused input and H.V. test leads
- Compact, lightweight enclosure with terminal guard and dust cover
- DIN rail mounting bracket
- Shock and vibration resistant construction
- Five year limited warranty
- Remote L.E.D. display and nameplate (optional)
- 1% or 2% switchboard meg ohm meter M/MU models only
Operation
Motor Guard applies a current limited, fixed dc voltage to the motor windings during idle periods. A solid state comparator circuit monitors measured leakage current to ground. An adjustable setpoint, factory preset to customer specifications, can be programmed to signal an alarm and lockout the equipment from operating if the set point is exceeded. The manual reset feature enables a return to operational status only after the fault condition has been corrected. Motor Guard will not impair normal operation of equipment being monitored.
Motor Guard GP500 Series Specifications
| Input Power |
115-125 VAC 50/60 Hz @.05 A max. |
| Test Voltage |
500 VDC @ 200 uA max. |
| Alarm Contacts |
5A @ 240 VAC or 28 VDC |
| Lockout Contacts |
5A @ 240 VAC or 28 VDC |
| L.E.D. Display |
Test on: green (flash); Fault: red (flash) |
| Control Accuracy |
2% overall |
| Ambient Temp. |
–14°F to 140°F |
| Dimensions (Inches) |
H 2.75 x W 2.25 x D 4.50 |
| Weight |
1 lb. |
| Assembly |
Meets UL 508 specifications |
Models
GP500
This is the base model. It connects to a single motor and has a test voltage of 500VDC. The GP500 is a "go/no go" unti. If the meg-ohm insulation resistance is in the safe range, it will allow the motor to start. If not it will lockout the starter circuit. Includes contacts for remote alarms or monitoring.
GP500-PS
All of the above plus a 2% meg=ohm panel meter.
GP500-MU 2%
This model has more reporting functions but still tests at 500 VDC. Includes a "pre-alarm" circuit that lights a yellow flashing LED when the motor enters the low insulation resistance range (yellow zone on the meter). It also has the lockout function when the motor enters the danger range (red zone on the meter). Has a test/calibrate feature that allows customization for an individual application.
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