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China Maximum Demand Indicator Suppliers | Bimetallic Movement and Combined Ammeter Factory
1. Measuring Range
1.1 Maximum Demand Indicator with Bimetallic Movement
1.2 Combined Maximum Demand Indicator with Bimetallic Moving-Iron Ammeter
Maximum Demand Indicator (MDI) is a panel mount meter. The thermal/time characteristics of MDI meters can monitor the most economic use of cable, protective devices, and transformers. It indicates the mean RMS current in the circuit within a given period of time and also records the maximum RMS current. Combining a moving-iron measuring system enables measurement of instantaneous values.
MDI can be divided into 3 categories:
- With bimetallic movement
- With moving-iron ammeter
- With alarm relay
- The demand value is indicated by the black moving pointer.
- The maximum demand value is indicated by the red slave pointer, which can be resumed by the reset knob.
- It can be lead-sealed for prevention of unauthorized reset.
Technical Specifications
| Parameter | Value / Description |
|---|---|
| Thermal Time Delay | 15 minutes |
| Accuracy Class | 3.0 (Precise reading starts from 25% of full scale) |
| Overload — Continuous | 1.2 times rated current |
| Overload — Short Duration | 10 times rated current for 1 second |
| Overload — With Saturating CT | 20 times rated current for 1 second |
| Power Consumption | < 3 VA |
MDI Categories
Type A
Maximum Demand Indicator with Bimetallic Movement
Measures the maximum load average value, indicated by the black pointer.
Type B
Combined MDI with Moving-Iron Ammeter
Measures maximum average load value (black horizontal pointer) and transient value (black vertical pointer). Accuracy class: 1.5.
2. Temperature Range of Operation
🌡️
Operating Range: -20°C to +40°C
All panel meters can operate trouble-free at room temperatures ranging from -20°C to +40°C.
3. Temperature Range of Storage
📦
Storage Range: -40°C to +70°C
4. Insulation Test
⚡
Test Voltage: 2 kV RMS
⏱️
Duration: 1 Minute
🔁
Frequency: 50 Hz
✅
Standard: IEC 61010-1
The test voltage is 2 kV RMS for 1 minute at a frequency of 50 Hz. All requirements conform to IEC 61010-1.
Frequently Asked Questions (FAQ)
Q
What is a Maximum Demand Indicator (MDI) and how does it work?
A Maximum Demand Indicator (MDI) is a panel-mount meter that monitors the mean RMS current in a circuit over a given period of time and records the maximum RMS current reached. It uses thermal/time characteristics to help ensure the most economic use of cables, protective devices, and transformers. The demand value is shown by a black moving pointer, while the peak maximum demand value is tracked by a red slave pointer.
Q
What are the different types of MDI meters available?
MDI meters are available in three main categories: (A) with bimetallic movement — measuring maximum average load value; (B) combined with a moving-iron ammeter — measuring both maximum average load and instantaneous transient values; and (C) with an alarm relay for alert-based applications.
Q
What is the accuracy class of the MDI meter?
The standard MDI meter has an accuracy class of 3.0, with precise readings starting from 25% of the full scale. The combined MDI with a moving-iron ammeter offers a higher accuracy class of 1.5 for the instantaneous transient value measurement.
Q
What overload capacity does the MDI meter support?
The MDI meter supports continuous overload of 1.2 times the rated current. For short durations, it can handle 10 times the rated current for 1 second. When used with a saturating CT, it supports up to 20 times the rated current for 1 second.
Q
What are the operating and storage temperature ranges for these panel meters?
All panel meters operate trouble-free within a temperature range of -20°C to +40°C. For storage, the acceptable temperature range is -40°C to +70°C, ensuring reliability across a wide range of environmental conditions.
Q
What insulation standard does the MDI meter comply with?
The MDI meter complies with IEC 61010-1. The insulation test is performed at 2 kV RMS for 1 minute at a frequency of 50 Hz, ensuring safe and reliable electrical insulation performance.