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A pulse capacitor in an impulse magnetizing system must do more than store energy. It must release that energy through the discharge circuit as a short, high-current magnetizing pulse.
In a capacitor-discharge magnetizer, the stored energy must be released through a switching device, busbars, connections, and a magnetizing coil within a very short period. Peak current, discharge speed, circuit inductance, and pulse conditions can therefore become critical to the actual magnetizing performance.
This makes pulse capacitor selection more demanding than simply choosing a larger capacitance.
In a capacitor-discharge impulse magnetizer, the pulse capacitor is first charged to the required voltage. When the discharge circuit is triggered, the stored energy is released through the switching device and magnetizing coil, generating the high-current pulse required for magnetization.
The energy stored in the capacitor is:
E = ½CV²
However, stored energy alone does not define the resulting magnetizing pulse. The discharge current and waveform are also affected by the total electrical characteristics of the circuit.
Capacitor inductance, switching components, busbars, connections, and the magnetizing coil all contribute to the discharge loop. Excessive inductance can limit current rise and influence how effectively the stored energy is transferred to the coil.
Research on capacitor-discharge impulse magnetizers has analyzed the capacitor, switching circuit, magnetizing fixture, and discharge current as parts of the same system. [1][2]
For impulse magnetizing, the capacitor must release stored energy into the magnetizing coil within a short discharge period. The required current pulse depends on the characteristics of the complete discharge circuit, not on capacitance alone.
CRE's MKMJ-S metal film pulse capacitor is used in high-energy pulse discharge systems. In an impulse magnetizer, it provides the stored energy for rapid discharge into the magnetizing coil, supporting the high-current pulse required for magnetization.
MKMJ-S pulse capacitors
One MKMJ-S configuration uses 4 × 125 μF ±5% at 2 kV DC, corresponding to approximately 1000 J of stored energy. Its maximum allowed charge/discharge current is ≤4 × 30 kA, while the capacitor's self-inductance is ≤100 nH. Under the specified rated conditions, its pulse life is at least 2,000,000 cycles.
The low self-inductance limits the capacitor's contribution to the total discharge-loop inductance. The switching device, busbars, connections, coil geometry, and physical layout still influence the final current waveform, so the pulse capacitor needs to be evaluated as part of the complete magnetizing circuit.
MKMJ-S is a metal film pulse capacitor for high-energy discharge applications, including impulse magnetizing and demagnetizing.
Its construction is intended for demanding pulse conditions, using a non-magnetic stainless-steel case, dry epoxy resin insulation, and M8 bolt terminals. Natural cooling is used, with an operating temperature range of -40°C to +55°C.
The combination of high current capability, low inductance, and long pulse life makes MKMJ-S suitable for pulse systems where energy must be released rapidly and repeatedly.
An impulse magnetizer doesn’t always require the same capacitor configuration. Charging voltage, peak current, pulse conditions, coil characteristics, and available installation space can vary from one system to another.
Tell us your required voltage, capacitance, peak current, pulse conditions, and installation space. CRE can evaluate the requirements and provide a suitable MKMJ-S configuration for your application.
What is a pulse capacitor used for in an impulse magnetizer?
A pulse capacitor stores electrical energy and releases it rapidly through the magnetizing coil to generate the high-current pulse required to magnetize a permanent magnet.
Why is low inductance important in an impulse magnetizer?
Low inductance helps reduce the capacitor's contribution to the total discharge-loop inductance, supporting faster current delivery during a short-duration, high-current pulse.
Does stored energy determine the magnetizing pulse?
No. Stored energy depends on capacitance and charging voltage, but the resulting current pulse is also influenced by circuit inductance, resistance, switching characteristics, and the magnetizing coil.
Is higher capacitance always better for an impulse magnetizer?
No. A larger capacitance increases stored energy at the same charging voltage, but the required configuration also depends on peak current, pulse duration, circuit characteristics, and coil requirements.
Can MKMJ-S be customized for different impulse magnetizers?
Yes. CRE can customize the capacitor according to the electrical and mechanical requirements of the magnetizing system, including voltage, capacitance, current capability, dimensions, terminals, and other construction requirements.
[1] Kim, P. S., Kim, Y., & Hong, B. An Investigation to General Characteristics of Impulse Magnetizer. I. Circuit, Thermal and Cost Modeling of Impulse Magnetizer. IEEE Industry Applications Conference, 1999. DOI: 10.1109/IAS.1999.805970.
[2] Takahashi, N. 3D analysis of magnetization distribution magnetized by capacitor-discharge impulse magnetizer. Journal of Materials Processing Technology, 2001, 108(2), 241–245. DOI: 10.1016/S0924-0136(00)00763-9.
