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Maximum Demand Indicator Suppliers in China - Bimetallic Movement & Combined Moving-Iron Ammeter Factory
1. Measuring Range
1.1 Maximum Demand Indicator with Bimetallic Movement
1.2 Combined Maximum Demand Indicator with Bimetallic Moving-Iron Ammeter
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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.
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MDI can be divided into 3 categories: with bimetallic movement, with moving-iron ammeter, or with alarm relay.
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The demand value is indicated by a black moving pointer. The maximum demand value is indicated by a red slave pointer, which can be resumed by a 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 × rated current |
| Overload — Short Duration | 10 × rated current for 1 second |
| With Saturating CT | 20 × rated current for 1 second |
| Power Consumption | < 3 VA |
MDI Categories
Category A
Maximum Demand Indicator with Bimetallic Movement
Measures the maximum load average value, indicated by the black pointer.
Category B
Combined Maximum Demand Indicator with Moving-Iron Ammeter
Measures maximum average load value (black horizontal pointer); transient value (black vertical pointer). Accuracy class: 1.5.
2. Temperature Range of Operation
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Operating Temperature
-20℃ to +40℃
⚠ Note: All panel meters can operate trouble-free at room temperatures ranging from -20℃ to +40℃.
3. Temperature Range of Storage
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Storage Temperature
-40℃ to +70℃
4. Insulation Test
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Test Voltage
2 kV RMS
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Duration
1 Minute
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Frequency
50 Hz
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Standard
IEC 61010-1
All requirements conform to IEC 61010-1. The insulation test voltage is 2 kV RMS for 1 minute at a frequency of 50 Hz.
Frequently Asked Questions (FAQ)
Q
What is a Maximum Demand Indicator (MDI) and what is it used for?
A Maximum Demand Indicator (MDI) is a panel-mounted meter designed to monitor and record the maximum RMS current in an electrical circuit over a defined period of time. It helps manage the most economic use of cables, protective devices, and transformers by tracking peak demand and mean load values.
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What are the different types of MDI meters available?
MDI meters are available in three main categories: (1) with bimetallic movement, (2) with moving-iron ammeter (combined type), and (3) with alarm relay. Each type serves specific measurement and monitoring requirements in electrical panel applications.
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How do the pointers on an MDI meter function?
The MDI meter uses two pointers: a black moving pointer that indicates the current demand value in real time, and a red slave pointer that records and holds the maximum demand value reached. The red pointer can be reset using a reset knob, and the meter can be lead-sealed to prevent unauthorized resets.
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What are the overload capabilities of the MDI meter?
The MDI meter supports continuous overload at 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 can withstand 20 times the rated current for 1 second.
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What is the operating and storage temperature range for MDI panel meters?
All MDI panel meters can operate reliably at temperatures ranging from -20℃ to +40℃. For storage purposes, the meters can be safely stored within a temperature range of -40℃ to +70℃ without any damage or performance degradation.
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What insulation test standard does the MDI meter comply with?
The MDI meter complies with IEC 61010-1. The insulation test is conducted at a test voltage of 2 kV RMS for 1 minute at a frequency of 50 Hz, ensuring the meter meets international safety and performance standards for electrical measurement equipment.